tag:theconversation.com,2011:/es/topics/thermoregulation-10959/articlesThermoregulation – The Conversation2024-02-12T04:57:01Ztag:theconversation.com,2011:article/2228632024-02-12T04:57:01Z2024-02-12T04:57:01ZCurious Kids: why do we shiver when we feel cold?<figure><img src="https://images.theconversation.com/files/574832/original/file-20240212-26-pv68gh.jpg?ixlib=rb-1.1.0&rect=33%2C0%2C3748%2C2496&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/sad-froze-teenage-caucasian-girl-shivering-2017458494">Georgy Dzyura/Shutterstock</a></span></figcaption></figure><blockquote>
<p><strong>“Why do we shiver when we feel cold?” – Syeda, age 10, from Karachi</strong></p>
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<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>What a cool question, Syeda!</p>
<p>Our bodies like to be nice and warm, usually <a href="https://www.ncbi.nlm.nih.gov/books/NBK331/">around 37°C</a>. This allows our internal functions to work at their best. But our bodies are constantly losing heat to the outside air.</p>
<p>When it’s cold outside, or if we jump into a cold swimming pool, or even if the air-conditioning is a bit strong, our body temperature can lower, sometimes to levels that are uncomfortable.</p>
<p>If our body temperature drops too low, our heart, nervous system and other organs are not able to work <a href="https://www.cdc.gov/niosh/topics/coldstress/coldrelatedillnesses.html">normally</a>. If it falls to extremely low temperatures, called hypothermia, this can cause some organs to <a href="https://www.mayoclinic.org/diseases-conditions/hypothermia/symptoms-causes/syc-20352682">completely fail</a>.</p>
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Read more:
<a href="https://theconversation.com/why-are-my-hands-and-feet-always-cold-and-when-should-i-be-worried-184154">Why are my hands and feet always cold? And when should I be worried?</a>
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<p>Luckily, our bodies have their own internal heaters to protect us against small changes in temperature. This is mostly thanks to the actions of our muscles, through a process called <a href="https://www.ncbi.nlm.nih.gov/books/NBK507838/">thermoregulation</a>. It’s this process that leads our bodies to shiver when we’re chilly.</p>
<h2>Muscles are our bodies’ personal heaters</h2>
<p>When our muscles twitch, they generate <a href="https://www.ted.com/talks/christian_moro_the_surprising_reason_our_muscles_get_tired">movement</a>. This is called “muscle contraction”, and can involve the muscles tightening and shortening. </p>
<p>Muscle contractions help us walk around, smile, lift heavy objects and high-five each other.</p>
<p>Moving our muscles also generates a bit of <a href="https://www.britannica.com/science/excretion/Types-of-waste-metabolic-and-nonmetabolic">heat</a>. With many <a href="https://www.youtube.com/watch?v=ZqwGTso2Wmc">muscles moving</a> most of the time, this helps our bodies stay nice and warm.</p>
<figure class="align-center ">
<img alt="A woman shivering." src="https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">We’ll often hunch our necks, tense up, and rub our shoulders when cold. Shivering usually follows to help warm us up.</span>
<span class="attribution"><span class="source">Christian Moro</span></span>
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<p>The more our muscles move, the more heat they generate. This is why you might feel hot and bothered after running around or playing sports.</p>
<p>On the other hand, when we stop moving our muscles, we start to cool down. This is one of the reasons we cover up with bedsheets at night.</p>
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Read more:
<a href="https://theconversation.com/yes-women-might-feel-the-cold-more-than-men-heres-why-184329">Yes, women might 'feel the cold' more than men. Here's why</a>
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<h2>What about the shiver?</h2>
<p><a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3167123/">Shivering</a> is the rapid contractions of our muscles over and over. This doesn’t generate any significant movement, but instead releases heat that helps to warm us up.</p>
<p>Most of the time we don’t have control over when our brain tells our muscles to shiver. We have special sensors throughout our <a href="https://www.ncbi.nlm.nih.gov/books/NBK507838/">body</a> that pick up when our system is cold, and our brain then responds by telling the muscles to start shivering.</p>
<p>And we aren’t the only ones who shiver! All <a href="https://www.khanacademy.org/science/ap-biology/ecology-ap/energy-flow-through-ecosystems/a/animal-temperature-regulation-strategies">mammals</a> have the ability to shiver, so your pet cat or dog might shiver when they’re cold too. Even <a href="https://www.fws.gov/story/how-do-birds-keep-warm-winter">birds</a> shiver.</p>
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Read more:
<a href="https://theconversation.com/curious-kids-if-our-bodies-are-happy-at-37-why-do-we-feel-so-unhappy-when-its-too-hot-outside-159134">Curious Kids: if our bodies are happy at 37℃, why do we feel so unhappy when it's too hot outside?</a>
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<p>When it’s a chilly day outside, you might also notice you get <a href="https://www.health.harvard.edu/blog/wondering-about-goosebumps-of-course-you-are-2020080320688">goosebumps</a>. Goosebumps happen when tiny muscles connected to the hair follicles (from which our hair grows) tighten. This causes the little hairs on our arms to stand up, helping to trap in warm air and slow down body heat loss to the outside.</p>
<h2>How can you ‘chill out’ your shiver?</h2>
<p>Thermoregulation is key to maintaining a nice, consistent body temperature, which keeps our internal organs happy.</p>
<p>While shivering can help us warm up, it’s best to make sure you wear the right clothes if you’re going to be out in the cold.</p>
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<p><em>Hello, Curious Kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au</em></p><img src="https://counter.theconversation.com/content/222863/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Shivering actually helps warm our bodies up.Charlotte Phelps, Senior Teaching Fellow, Medical Program, Bond UniversityChristian Moro, Associate Professor of Science & Medicine, Bond UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2173682024-01-24T23:40:59Z2024-01-24T23:40:59ZExtreme heat can be risky during pregnancy. How to look after yourself and your baby<figure><img src="https://images.theconversation.com/files/570779/original/file-20240123-25-6rr05.jpg?ixlib=rb-1.1.0&rect=0%2C20%2C6709%2C4446&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/kid-kissing-belly-her-mom-633713483">Shutterstock</a></span></figcaption></figure><p>As we face the continued effects of <a href="https://www.lancetcountdown.org/2023-report/">climate change</a>, the frequency and intensity of heatwaves is increasing. We’ve recently learnt 2023 was <a href="https://www.climatecouncil.org.au/resources/2023-named-hottest-year-record-scorching-temps-sweep-australia/">the hottest year</a> on record.</p>
<p>Extreme heat presents a major public health threat. It can be <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01208-3/fulltext">especially dangerous</a> for people who are socioeconomically disadvantaged, and people who have reduced physiological ability to adapt, such as older adults and those with certain medical conditions.</p>
<p>Pregnant people are also more vulnerable, with evidence showing exposure to extreme heat <a href="https://pubmed.ncbi.nlm.nih.gov/37501633/">is associated with</a> increased risks for the baby.</p>
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Read more:
<a href="https://theconversation.com/health-check-can-stress-during-pregnancy-harm-my-baby-81825">Health Check: can stress during pregnancy harm my baby?</a>
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<h2>What are the risks?</h2>
<p>Globally one stillbirth occurs <a href="https://www.unicef.org/reports/neglected-tragedy-global-burden-of-stillbirths-2020">every 16 seconds</a> and <a href="https://pubmed.ncbi.nlm.nih.gov/30389451/">15 million babies</a> are born preterm (before 37 complete weeks of pregnancy) every year. Complications of preterm birth are the leading cause of death and disability for children aged under five years old. </p>
<p>A <a href="https://pubmed.ncbi.nlm.nih.gov/33148618/">systematic review</a> which included studies from 27 countries showed that for every 1˚C increase in ambient (environmental) temperature, the risk for preterm birth and stillbirth increased by 5%.</p>
<p>The risk of stillbirth and preterm birth attributed to heat is greater in lower- and middle-income countries where women are often employed in agriculture or other manual labour positions, and their work continues until <a href="https://pubmed.ncbi.nlm.nih.gov/35237548/">the end of their pregnancy</a>. </p>
<p>Within high-income countries the risk <a href="https://pubmed.ncbi.nlm.nih.gov/34951022/">is greater</a> in <a href="https://pubmed.ncbi.nlm.nih.gov/35710419/">disadvantaged populations</a>.</p>
<p>Recent Australian research has also suggested a mother’s exposure to extreme temperatures may <a href="https://ehp.niehs.nih.gov/doi/10.1289/EHP12660">influence a baby’s birth weight</a>. </p>
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<a href="https://images.theconversation.com/files/570781/original/file-20240123-17-77i0s4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="woman drinks glass of water" src="https://images.theconversation.com/files/570781/original/file-20240123-17-77i0s4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/570781/original/file-20240123-17-77i0s4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570781/original/file-20240123-17-77i0s4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570781/original/file-20240123-17-77i0s4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570781/original/file-20240123-17-77i0s4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570781/original/file-20240123-17-77i0s4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570781/original/file-20240123-17-77i0s4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Make sure you stay hydrated while pregnant.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/pregnant-water-drinking-woman-young-pregnancy-2177419759">Shutterstock</a></span>
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Read more:
<a href="https://theconversation.com/5-expert-tips-on-how-to-look-after-your-baby-in-a-heatwave-216906">5 expert tips on how to look after your baby in a heatwave</a>
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<p>Pregnant people are thought to be at increased risk of heat stress due to changes in their body’s capacity to <a href="https://pubmed.ncbi.nlm.nih.gov/37501633/">regulate temperature</a>. These changes include:</p>
<ul>
<li><p>increased body mass and body fat which reduces a pregnant woman’s ability to dissipate heat to the environment </p></li>
<li><p>decreased ratio of surface area to body mass can make sweating less effective</p></li>
<li><p>additional energy produced from the baby increases the mother’s core body temperature. </p></li>
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<h2>The effects on the body and baby</h2>
<p>When the ambient environment is hotter than the pregnant woman’s core body temperature (that is when the air temperature reaches around 38 degrees or above) blood flow is diverted to the skin to allow sweating. This can decrease blood flow to the placenta, meaning less nutrition and oxygen to the baby.</p>
<p>If dehydration occurs, hormonal changes can include the release of prostaglandin and oxytocin, potentially triggering labour prematurely. </p>
<p>Heat exposure can also release heat-shock protein (a family of proteins produced by cells secondary to stressful conditions) which can damage placental cells and placental function. This can contribute to poor fetal nutrition, leading to <a href="https://pubmed.ncbi.nlm.nih.gov/30594173/">low birth weight</a>. </p>
<p>However, actual thermo-physiological data from pregnant women during heat exposure is sparse. Our <a href="https://pubmed.ncbi.nlm.nih.gov/29496695/">recent review</a> showed no study has assessed thermoregulatory function in pregnant women at temperatures higher than 25˚C. </p>
<p>Our subsequent <a href="https://pubmed.ncbi.nlm.nih.gov/34165763/">climate chamber study</a> with pregnant women showed their bodies regulate temperature up to 32˚C as well as non-pregnant women.</p>
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<a href="https://images.theconversation.com/files/570775/original/file-20240123-15-zkxgxo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Woman in sun hat sits with legs in swimming pool. She appears pregnant." src="https://images.theconversation.com/files/570775/original/file-20240123-15-zkxgxo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/570775/original/file-20240123-15-zkxgxo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570775/original/file-20240123-15-zkxgxo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570775/original/file-20240123-15-zkxgxo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570775/original/file-20240123-15-zkxgxo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570775/original/file-20240123-15-zkxgxo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570775/original/file-20240123-15-zkxgxo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Dipping your feet into a cool pool can help you and your baby cool off.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/beautiful-young-pregnant-woman-sitting-near-422267806">Tanya Yatsenko/Shutterstock</a></span>
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Read more:
<a href="https://theconversation.com/dont-like-drinking-plain-water-10-healthy-ideas-for-staying-hydrated-this-summer-191859">Don’t like drinking plain water? 10 healthy ideas for staying hydrated this summer</a>
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<h2>5 ways to beat the heat while pregnant</h2>
<p>Evidence of the effectiveness of interventions that address acute heat exposure during pregnancy specifically are limited. Air-conditioning is exceptionally protective, however it is unaffordable for many in Australia and globally. </p>
<p>More evidence of the effect of extreme heat on pregnancy outcomes at a population level in both low and high income countries will help us develop ways to protect pregnant people and the community. </p>
<p>In the meantime, with the threat of more very hot summer days, simple strategies to <a href="https://www.health.nsw.gov.au/environment/beattheheat/pages/default.aspx">beat the heat</a> when pregnant include:</p>
<p><strong>1) Drink enough water</strong> – take a water bottle with you when out and about</p>
<p><strong>2) Plan your day</strong> – avoid the hottest part of the day if you can. Take a hat or umbrella with you for shade</p>
<p><strong>3) Stay cool</strong> – use fans or air-conditioning if possible, close blinds and curtains, visit a cooled public environment </p>
<p><strong>4) Dress down</strong> – wear lightweight, long-sleeved, light-coloured, loose-fitting clothes made from natural fibres, such as cotton or linen</p>
<p><strong>5) Go to sleep on your side</strong> – at night and for daytime naps to allow the <a href="https://theconversation.com/five-ways-to-reduce-the-risk-of-stillbirth-108253">best blood flow to the baby</a>.</p>
<p>These strategies need to be adapted to personal circumstances, and of course seek medical advice if you feel unwell. Signs of heat exhaustion that can lead to <a href="https://www.healthdirect.gov.au/heatstroke">heat stroke</a> if not treated early include:</p>
<ul>
<li>sweating and pale, cool, damp skin</li>
<li>dizziness and weakness</li>
<li>a headache</li>
<li>nausea or vomiting</li>
<li>a rapid pulse and fast, shallow breathing</li>
<li>muscle cramps </li>
<li>fainting</li>
<li>feeling restless and anxious</li>
<li>heat rash.</li>
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Read more:
<a href="https://theconversation.com/its-extremely-hot-and-im-feeling-weak-and-dizzy-could-i-have-heat-stroke-215084">It's extremely hot and I'm feeling weak and dizzy. Could I have heat stroke?</a>
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<p>If you have these symptoms, find a cool place to rest, drink cool water or a rehydration drink, remove excess clothing, have a cool shower or bath, or sit for a while with your feet in cool water.</p>
<p>More severe symptoms indicating heatstroke include intense thirst, slurred speech, lack of coordination or confusion, and aggressive or strange behaviour. Heatstroke is a medical emergency, so call triple 0.</p>
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Read more:
<a href="https://theconversation.com/five-ways-to-reduce-the-risk-of-stillbirth-108253">Five ways to reduce the risk of stillbirth</a>
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<img src="https://counter.theconversation.com/content/217368/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Adrienne Gordon receives funding from MRFF, NHMRC and Wellcome Trust. She is affiliated with the International Stillbirth Alliance, the NHMRC Stillbirth Centre of Research Excellence, The Perinatal Society of Australia and New Zealand, The Sydney Institute for Women, Children and their Families, Womens Healthcare Australasia and RedNose Australia. </span></em></p><p class="fine-print"><em><span>Camille Raynes-Greenow receives funding from NHMRC, Wellcome Trust, ERLA, UK. </span></em></p><p class="fine-print"><em><span>Ollie Jay receives funding from National Health and Medical Research Council, Wellcome Trust, NSW Health, NSW Dept of Planning, Industry and Environment, and the NSW Reconstruction Authority (formerly Resilience NSW), Tennis Australia.</span></em></p>During pregnancy, the body’s capacity to regulate temperature changes. Here’s how to cool down and the overheating red flags to watch out for.Adrienne Gordon, Neonatal Staff Specialist, NHMRC Early Career Research Fellow, University of SydneyCamille Raynes-Greenow, Professor and Deputy Head of School, Sydney School of Public Health, University of SydneyOllie Jay, Professor of Heat & Health; Director of Heat & Health Research Incubator; Director of Thermal Ergonomics Laboratory, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2169062023-12-06T22:04:49Z2023-12-06T22:04:49Z5 expert tips on how to look after your baby in a heatwave<figure><img src="https://images.theconversation.com/files/562908/original/file-20231201-21-qxkftk.jpg?ixlib=rb-1.1.0&rect=1%2C0%2C997%2C667&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/baby-being-washed-face-down-during-2217329091">b-finity/Shutterstock</a></span></figcaption></figure><p>Extreme heat events are becoming more <a href="https://www.acs.gov.au/pages/heatwaves">frequent and intense</a> in Australia. This can cause illness or worsen existing conditions. During hot weather, hospital admissions and deaths <a href="https://www.climatechange.environment.nsw.gov.au/impacts-climate-change/weather-and-oceans/heatwaves">increase</a>.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1732139339596083256"}"></div></p>
<p>Babies are among those particularly vulnerable.</p>
<p>Looking after a baby during extreme heat takes a little planning and a lot of patience. Here are five practical tips.</p>
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Read more:
<a href="https://theconversation.com/extreme-weather-is-landing-more-australians-in-hospital-and-heat-is-the-biggest-culprit-216440">Extreme weather is landing more Australians in hospital – and heat is the biggest culprit</a>
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<h2>Why are babies particularly at risk?</h2>
<p>Babies are more vulnerable to extreme heat for several reasons.</p>
<p>They have a <a href="https://www.science.org/doi/10.1126/science.abe5017">higher metabolic rate</a> than older children and adults, so their body generates more internal heat. </p>
<p>They also have a larger surface area compared with the volume of their body. So they <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6770410">adsorb heat</a> more easily from the environment. </p>
<p>Their sweat glands are <a href="https://www.livescience.com/newborns-no-tears-or-sweat.html">not fully developed</a>. So they cannot lose heat by sweating as easily as older children and adults.</p>
<p>Babies also have to rely on adults to keep them safe when the weather is hot. They cannot move to a cooler place or drink more fluids without help from their parents or caregivers.</p>
<h2>1. Plan ahead</h2>
<p>Knowing if hot weather is coming allows you to prepare and avoid, or reduce, your baby’s exposure to heat. </p>
<p>So keep an eye on forecasts from the <a href="http://www.bom.gov.au/">Bureau of Meteorology</a> (including its <a href="http://www.bom.gov.au/australia/heatwave/">heatwave warning service</a>). Your local <a href="https://www.abc.net.au/local">ABC radio station</a> broadcasts emergency information, and you can search for emergency conditions on the <a href="https://www.abc.net.au/emergency">ABC website</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/worried-about-heat-and-fire-this-summer-heres-how-to-prepare-212443">Worried about heat and fire this summer? Here's how to prepare</a>
</strong>
</em>
</p>
<hr>
<h2>2. Keep your home cool</h2>
<p>On hot days, close windows, blinds and curtains early in the day and keep outside doors shut. If you live in a multi-storey building, stay downstairs where the air will be cooler. </p>
<p>Air conditioning will keep you cool if you have it. Staying in one part of the house and closing doors to the rest, can make air conditioning more effective and reduce your energy use. Take care to ensure rooms do not become too cold and ensure air flow from air conditioners or fans is not directed at your baby. That’s because babies also have difficulty <a href="https://www.chop.edu/conditions-diseases/warmth-and-temperature-regulation">regulating their temperature</a> in the cold and their temperature can quickly drop. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/562923/original/file-20231201-25-pkaqll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Fan on chest of drawers, cot in background" src="https://images.theconversation.com/files/562923/original/file-20231201-25-pkaqll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/562923/original/file-20231201-25-pkaqll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/562923/original/file-20231201-25-pkaqll.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/562923/original/file-20231201-25-pkaqll.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/562923/original/file-20231201-25-pkaqll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/562923/original/file-20231201-25-pkaqll.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/562923/original/file-20231201-25-pkaqll.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Make sure your fan isn’t blowing directly at your baby.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/modern-fan-on-commode-baby-room-1897747780">New Africa/Shutterstock</a></span>
</figcaption>
</figure>
<p>Power blackouts are <a href="https://www.energynetworks.com.au/resources/fact-sheets/heatwaves-and-energy-supply-explained/#:%7E:text=Heatwaves%20are%20three%20or%20more,faults%2C%20bushfires%20or%20generator%20faults.">common</a> during extreme heat events. So, think about what you’ll do if you can’t use air conditioning because of a blackout.</p>
<p>If you cannot keep cool at home, try to find somewhere you can go that is air conditioned. This could be a public building, such as a library or shopping centre, or the home of a friend or relative. </p>
<p>Some communities have “<a href="https://www.smh.com.au/national/nsw/no-way-to-escape-the-heat-push-for-havens-to-stop-australia-s-silent-killer-20230816-p5dwzl.html">heat havens</a>” or “<a href="https://www.smh.com.au/national/nsw/homes-aren-t-safe-western-sydney-prepares-evacuation-shelters-for-hot-summers-20220505-p5aioj.html">heat shelters</a>” where vulnerable people, including pregnant women and families with babies, can go during extreme heat.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/evacuating-with-a-baby-heres-what-to-put-in-your-emergency-kit-127026">Evacuating with a baby? Here's what to put in your emergency kit</a>
</strong>
</em>
</p>
<hr>
<h2>3. Take care if you need to go out</h2>
<p>If you do have to go out, ensure your baby is sheltered from the sun and heat as much as possible. </p>
<p>Use a sunshade on car windows to protect you baby from direct sunlight. Never leave a baby or young child <a href="https://raisingchildren.net.au/toddlers/safety/car-pedestrian-safety/never-leave-children-in-cars">in a parked car</a>.</p>
<p>You can help keep your baby cool in their pram by covering it with a light, damp cloth and spraying it with water every 15-20 minutes. Don’t let the cloth dry out completely because this can <a href="https://theconversation.com/covering-your-babys-pram-with-a-dry-cloth-can-increase-the-temperature-by-almost-4-degrees-heres-what-to-do-instead-199099">increase the temperature</a> in the pram.</p>
<p>Once the day starts to cool down, playing with water in a shady spot outside is a great way to cool down. Always supervise babies in or near water.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1629708787866038272"}"></div></p>
<h2>4. Offer babies extra fluids</h2>
<p>Babies need extra fluids during hot weather, but their pattern of feeding can change when it’s hot.</p>
<p>For breastfed babies this often means they start fussing or crying at the breast after just a few minutes, then want to breastfeed again as soon as 30-40 minutes later. </p>
<p>Mothers may worry their breasts have run out of milk, but they haven’t. These short feeds provide milk that is <a href="http://www.foodandnutritionjournal.org/volume2number2/importance-of-exclusive-breastfeeding-and-complementary-feeding-among-infants/">higher in water</a> than a longer breastfeed. </p>
<p>Just like adults, babies don’t want to eat a full meal when they’re hot. Once the day starts to cool down, most babies will have several <a href="https://www.breastfeeding.asn.au/resources/breastfeeding-hot-weather">longer, more satisfying feeds</a>.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1730246909317579131"}"></div></p>
<p>Similarly, formula-fed babies will often take less milk at a feed during the heat of the day but look for another feed sooner than usual.</p>
<p>Instead of trying to make a baby finish a whole bottle, try splitting their usual feed into two. If the baby finishes the first bottle, you can top it up from the second bottle or keep it in the fridge and warm it up again when they start <a href="https://www.breastfeeding.asn.au/resources/feeding-cues">looking hungry</a> again. Just like breastfed babies, they will usually be looking for slightly bigger feeds as the day starts to cool. </p>
<p>Do NOT give babies under six months old water as this can make them very ill. Their kidneys are not mature and <a href="https://www.reuters.com/article/us-water-babies-idUSCOL16728820080521">cannot handle the extra water</a>.</p>
<p>You can tell your baby is getting enough fluids if they have <a href="https://www.breastfeeding.asn.au/resources/baby-getting-enough-breastmilk">five heavy, wet disposable nappies</a> in 24 hours, their urine is pale yellow and doesn’t have a strong smell. </p>
<p>If this isn’t happening, your baby <a href="https://www.health.nsw.gov.au/environment/beattheheat/Pages/babies-children-hot-weather.aspx">needs more fluids</a> and you need to offer more frequent feeds. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/562925/original/file-20231201-23-pkaqll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Baby chewing on water melon outside in grassy garden or park" src="https://images.theconversation.com/files/562925/original/file-20231201-23-pkaqll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/562925/original/file-20231201-23-pkaqll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/562925/original/file-20231201-23-pkaqll.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/562925/original/file-20231201-23-pkaqll.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/562925/original/file-20231201-23-pkaqll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/562925/original/file-20231201-23-pkaqll.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/562925/original/file-20231201-23-pkaqll.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">For older babies, try offering watermelon or strawberries.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/little-boy-eating-watermelon-red-garden-459152617">Dudaeva/Shutterstock</a></span>
</figcaption>
</figure>
<p>From six months, babies can be given small amounts of <a href="https://www.health.tas.gov.au/publications/drinking-water-babies-fact-sheet">cooled boiled water</a> in addition to breastmilk or formula. You can also offer foods containing lots of water, such as watermelon or strawberries, or iceblocks made with breastmilk, formula or diluted fruit juice. Chewing on a cold, wet face washer is another way older babies can get extra fluids.</p>
<p>Remember to look after yourself when the weather gets hot. Have a glass of water at least every time your baby feeds. If you are breastfeeding and the heat makes skin contact uncomfortable for you and your baby, you can put a light cloth or damp hand-towel between you, or you can lie down to feed so your baby is next to your body instead of on it.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-how-do-i-tell-if-im-dehydrated-107437">Health Check: how do I tell if I'm dehydrated?</a>
</strong>
</em>
</p>
<hr>
<h2>5. Prepare for sleep</h2>
<p>Everyone struggles to sleep in hot weather. A lukewarm bath may help your baby cool off enough to fall asleep. However, avoid cold baths as your baby’s temperature may drop too much. </p>
<p>Nobody sleeps well on hot nights and we all need to catch up on sleep when the weather cools.</p>
<hr>
<p><em>In extreme heat, if your baby won’t feed well, is limp or floppy, has dull sunken eyes and a sunken soft spot in the skull (fontanelle), seek medical treatment straight away. In an emergency, call 000.</em></p><img src="https://counter.theconversation.com/content/216906/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Karleen Gribble is project lead on the Australian Breastfeeding Association's Community Protection for Infants and Young Children in Bushfire Emergencies Project and is an Australian Breastfeeding Association Educator and Counsellor. Karleen is also on the steering committee of the international interagency collaboration the Infant and Young Child Feeding in Emergencies Core Group and has been involved in the development of international guidance and training on infant and young child feeding in emergencies for over a decade.
</span></em></p><p class="fine-print"><em><span>Michelle Hamrosi is the community engagement officer on the Australian Breastfeeding Association's Community Protection for Infants and Young Children in Bushfire Emergencies Project. Michelle is also a general practitioner and an international board certified lactation consultant. Michelle volunteers as a breastfeeding counsellor and group leader for the Australian Breastfeeding Association Eurobodalla group. She is also a member of Doctors for the Environment, Climate and Health Alliance and Australian Parents for Climate Action.</span></em></p><p class="fine-print"><em><span>Nina Chad is an infant and young child feeding consultant for the World Health Organization. She is a member of the Public Health Association of Australia, the World Public Health Nutrition Association, and the Australian Breastfeeding Association.</span></em></p>Looking after a baby during extreme heat events takes a little planning and a lot of patience. Here are some practical steps you can take.Karleen Gribble, Adjunct Associate Professor, School of Nursing and Midwifery, Western Sydney UniversityMichelle Hamrosi, Clinical lecturer, Rural Clinical School, Australian National UniversityNina Jane Chad, Research Fellow, University of Sydney School of Public Health, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2013802023-06-15T02:07:48Z2023-06-15T02:07:48ZBig hair? Bald? How much difference your hair really makes to keep you cool or warm<figure><img src="https://images.theconversation.com/files/525825/original/file-20230512-21-gwsojg.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1000%2C666&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/close-photo-beautiful-she-her-wear-1776598856">Shutterstock</a></span></figcaption></figure><p>We have <a href="https://theconversation.com/health-check-why-does-womens-hair-thin-out-39126">millions</a> of hair follicles on our body, including around 100,000 on our scalp. </p>
<p>This might sound like a lot of hair, yet humans are described as “hairless”. We have evolved to be the only mammals with a relatively hairless body, but still with scalp hair.</p>
<p>So how does your hair affect your body temperature when it’s hot or cold? </p>
<p>Compared with other animals, our hair does not have as much influence on keeping us warm or cool as you might think. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-why-do-some-people-feel-the-cold-more-than-others-37805">Health Check: why do some people feel the cold more than others?</a>
</strong>
</em>
</p>
<hr>
<h2>Essential to our survival</h2>
<p>Our brain function and body’s metabolism depend on an optimal temperature of around 37°C. Thermoregulation maintains this body temperature, even when we are exposed to a hotter or colder external temperature.</p>
<p>For non-human mammals, body hair or fur plays a role in protecting against environmental cold or heat. </p>
<p>For instance, a heavy fur coat helps keep a polar bear <a href="https://polarbearsinternational.org/polar-bears-changing-arctic/polar-bear-facts/adaptions-characteristics/">warm</a> in the cold. But fur also keeps an animal cool in the heat because it can <a href="https://www.jstor.org/stable/25064866">absorb or reflect</a> radiant heat. </p>
<p>Scientists think this is why humans have kept hair on our heads. Our heads are exposed to the most heat from the sun, and scalp hair keeps our heads cool. </p>
<p>Research published just last week <a href="https://www.pnas.org/doi/10.1073/pnas.2301760120">suggests</a> curly hair provides the best heat protection. That’s because curly hair’s thicker layer of insulation reduces the amount of sun that reaches the scalp.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Four people arm in arm walking along dirt road" src="https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=490&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Curly hair may provide the best protection.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/friends-walking-travel-young-people-nature-2212936811">Shutterstock</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-humid-is-it-3-things-to-keep-you-cool-in-a-hot-and-sticky-summer-and-3-things-that-wont-176365">How humid is it? 3 things to keep you cool in a hot and sticky summer (and 3 things that won't)</a>
</strong>
</em>
</p>
<hr>
<h2>But hair is not the only factor</h2>
<p>When humans moved from living in the jungle to the savannah, they needed to walk and run long distances in the sun. This meant they needed a way to handle the increased body temperature that comes with physical activity in the heat. </p>
<p>Sweating is the best way to lose heat and cool down, but the presence of hair reduces sweating and heat loss from the skin.</p>
<p>So humans evolved to <a href="https://www.pnas.org/doi/10.1073/pnas.1113915108">lose body hair</a> to be better adapted to exercising in the heat. Fewer hair follicles in our skin made room for more sweat glands. This made our skin optimal for sweat evaporation – and the <a href="https://theconversation.com/want-to-keep-cool-on-hot-summer-days-heres-how-34489">heat loss</a> that goes with it – to keep us cool.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-art-of-balding-a-brief-history-of-hairless-men-199531">The art of balding: a brief history of hairless men</a>
</strong>
</em>
</p>
<hr>
<h2>So what’s best in the heat?</h2>
<p>You might think removing body hair or having a bald head is best for sweating and keeping cool when exercising in the heat. However, it’s not that simple.</p>
<p>Removing head hair would increase the <a href="https://www.pnas.org/doi/10.1073/pnas.2301760120">amount of sun</a> that reaches your scalp. This means you would need to <a href="https://pubmed.ncbi.nlm.nih.gov/20683812/">sweat more</a> during exercise in the sun to reduce an increase in body temperature, but not by much.</p>
<p>In fact, it’s the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4667044/#:%7E:text=The%20body%20hair%20is%20advantageous,heat%20removal%20during%20heat%20stress.">least hairy</a>
areas of our body that have the highest sweat rates during exercise. These are our forehead, neck, feet and hands.</p>
<p>So the best way to keep cool in the heat is to keep these areas uncovered (but still use sunscreen). Removing body hair will not have a large impact on your overall sweat rate.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Bald man combing head" src="https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Going bald or thinking of shaving your head? It won’t much affect your overall sweat rate.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/nostalgic-man-comb-his-bald-head-180040100">Shutterstock</a></span>
</figcaption>
</figure>
<h2>How about when it’s cold?</h2>
<p>Our body hair and head hair theoretically have a role in keeping us warm, but the effects are minimal.</p>
<p>When we are cold, the muscles of the hair follicles on the body contract to cause the hairs to stand straight. This is an attempt to trap heat close to the body and we see this as goosebumps. However, because our body hair is so thin, this does not have a big effect in keeping us warm.</p>
<p>Our head hair can prevent some heat loss from the head, but again this is limited. </p>
<p>When it’s cold, heat can still be lost through the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4667044/#:%7E:text=The%20body%20hair%20is%20advantageous,heat%20removal%20during%20heat%20stress.">skin of the head</a> regardless of your hairstyle. </p>
<p>The scalp also has only a very thin layer of fat compared to the rest of our skin, so our head has less insulation to protect against the cold. </p>
<p>A warm hat or beanie is the only way to prevent too much heat lost from the head.</p>
<h2>In a nutshell</h2>
<p>Our head and body hair, or lack of it, does have a small role in how you maintain your body temperature. </p>
<p>But overall, your hairstyle does not influence whether you feel warm or cool.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/ive-always-wondered-why-did-mammals-go-the-fur-route-rather-than-developing-feathers-103905">I've Always Wondered: why did mammals go the fur route, rather than developing feathers?</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/201380/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Theresa Larkin does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Keeping warm in winter and cool in summer is down to more than the length of your hair.Theresa Larkin, Associate professor of Medical Sciences, University of WollongongLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1990852023-02-10T01:50:05Z2023-02-10T01:50:05ZIs my medicine making me feel hotter this summer? 5 reasons why<figure><img src="https://images.theconversation.com/files/508796/original/file-20230208-24-lf74uh.jpg?ixlib=rb-1.1.0&rect=2%2C1%2C995%2C664&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/overheated-woman-sitting-on-couch-waving-1707953323">Shutterstock</a></span></figcaption></figure><p>If you’re really feeling the heat this summer, it might be down to more than the temperature outside.</p>
<p>Some types of medicines can increase your core body temperature or make you feel hotter than you really are. Some can affect your body’s ability to cool down.</p>
<p>Here’s what you need to know about heat intolerance and medicines.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-to-cope-with-extreme-heat-days-without-racking-up-the-aircon-bills-128857">How to cope with extreme heat days without racking up the aircon bills</a>
</strong>
</em>
</p>
<hr>
<h2>What is heat intolerance?</h2>
<p>Some people simply dislike the feeling of feeling hot, while others feel hot at temperatures most people find comfortable. Both are examples of
<a href="https://www.medicalnewstoday.com/articles/325232#symptoms">heat intolerance</a>.</p>
<p>Typical symptoms during warm weather include excessive sweating (or not sweating enough), exhaustion and fatigue, nausea, vomiting or dizziness, and changes in mood.</p>
<p>A number of factors can cause heat intolerance.</p>
<p>This includes the disorder <a href="https://my.clevelandclinic.org/health/diseases/6004-dysautonomia">dysautonomia</a>, which affects people’s autonomic nervous system – the part of the body that regulates the automatic functions of the body, including our response to heat. </p>
<p>Conditions such as diabetes, alcohol misuse, <a href="https://theconversation.com/what-causes-parkinsons-disease-what-we-know-dont-know-and-suspect-57579">Parkinson’s disease</a>, the autoimmune disease <a href="https://theconversation.com/explainer-what-is-guillain-barre-syndrome-and-is-it-caused-by-the-zika-virus-53884">Guillain-Barré syndrome</a> and <a href="https://theconversation.com/explainer-what-are-mitochondria-and-how-did-we-come-to-have-them-83106">mitochondrial disease</a> can cause dysautonomia. People in old age, those with some neurological conditions, or people less physically fit may also have it.</p>
<p>But importantly, medications can also contribute to heat intolerance.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/5-reasons-to-check-on-your-elderly-neighbour-during-a-heatwave-196218">5 reasons to check on your elderly neighbour during a heatwave</a>
</strong>
</em>
</p>
<hr>
<h2>1. Your body temperature rises</h2>
<p>Some medicines directly increase your body temperature, which then increases the risk of heat intolerance. </p>
<p>These include <a href="https://bpspubs.onlinelibrary.wiley.com/doi/epdf/10.1111/bph.15465">stimulant medications</a> to treat ADHD (attention deficit hyperactivity disorder), such as methylphenidate, dexamfetamine and lisdexamfetamine.</p>
<p><a href="https://www.healthdirect.gov.au/antipsychotic-medications">Antipsychotic medications</a> (such as clozapine, olanzapine and quetiapine) used to treat mental health conditions, such as schizophrenia and bipolar disorder, are other examples. </p>
<p>These ADHD and antipsychotic medicines raise your temperature by acting on the hypothalamus, the region of the brain essential for cooling.</p>
<p>The drug levothyroxine, used to treat an under-active thyroid, also increases your body temperature, this time by <a href="https://www.ncbi.nlm.nih.gov/books/NBK500006/">increasing your metabolism</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Medical illustration of hypothalamus region of brain" src="https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Some medicines raise your body temperature directly by acting on the hypothalamus region of the brain.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/3d-rendered-medically-accurate-illustration-hypothalamus-1292650669">SciePro/Shutterstock</a></span>
</figcaption>
</figure>
<h2>2. Your blood flow is affected</h2>
<p>Other medicines constrict (tighten) blood vessels, decreasing blood flow to the skin, and so prevent heat from escaping this way. This means your body can’t regulate its temperature as well in the heat. </p>
<p>Examples include <a href="https://www.healthdirect.gov.au/beta-blockers">beta-blockers</a> (such as metoprolol, atenolol and propranolol). These medications are used to treat conditions such as high blood pressure, angina (a type of chest pain), tachycardia (fast heart rate), heart failure, and to prevent migraines. </p>
<p><a href="https://www.nhs.uk/conditions/decongestants/">Decongestants</a> for blocked noses (for example, pseudoephedrine and phenylephrine), triptans for migraines (such as sumatriptan and zolmitriptan) and the ADHD medications mentioned earlier can also act to decrease blood flow to the skin.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/forget-nose-spray-good-sex-clears-a-stuffy-nose-just-as-effectively-and-is-a-lot-more-fun-167901">Forget nose spray, good sex clears a stuffy nose just as effectively — and is a lot more fun</a>
</strong>
</em>
</p>
<hr>
<h2>3. You can get dehydrated</h2>
<p>Other medicines can cause dehydration, which then makes you more susceptible to heat intolerance. The best examples are <a href="https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/in-depth/diuretics/art-20048129">diuretics</a> such as furosemide, hydrochlorothiazide, acetazolamide and aldosterone.</p>
<p>These are used to control high blood pressure and heart failure by forcing your kidneys to remove more fluid from your body. </p>
<p>Laxatives, such as senna extract and bisacodyl, also remove water from your body and so have a similar effect.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-how-do-i-tell-if-im-dehydrated-107437">Health Check: how do I tell if I'm dehydrated?</a>
</strong>
</em>
</p>
<hr>
<h2>4. You can sweat less</h2>
<p>Other medicines have a drying effect. This can be needed for medicines to do their job (for instance, to dry up a runny nose). For others, it is an unwanted side effect. </p>
<p>This drying reduces the amount you sweat, making it harder to lose heat and regulate your core temperature. A number of medicines have these effects, including:</p>
<ul>
<li>some antihistamines (such as promethazine, doxylamine and diphenhydramine)</li>
<li>certain antidepressants (such as amitriptyline, clomipramine and dothiepin)</li>
<li>medicines used to treat <a href="https://www.healthdirect.gov.au/urinary-incontinence#:%7E:text=Urinary%20incontinence%2C%20or%20poor%20bladder%20control%2C%20is%20very%20common%20in,to%20cure%20or%20improve%20it.">urinary incontinence</a> (for example, oxybutynin and solifenacin) </li>
<li>nausea medicine (prochlorperazine)</li>
<li>medicines for stomach cramps and spasms (for instance, hyoscine) </li>
<li>the antipsychoptics chlorpromazine, olanzapine, quetiapine and clozapine.</li>
</ul>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-do-men-really-sweat-more-than-women-73903">Health Check: do men really sweat more than women?</a>
</strong>
</em>
</p>
<hr>
<h2>5. You don’t feel thirsty</h2>
<p>Finally, some medicines, such as the antipsychotics haloperidol and droperidol, can aggravate heat intolerance by reducing your ability to feel thirsty. </p>
<p>If you don’t feel thirsty, you drink less and are therefore at risk of dehydration and feeling hot.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Woman staring at glass of water on counter" src="https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">People taking some medications just don’t feel thirsty.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/upset-young-woman-looking-through-glass-754782025">Shutterstock</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-how-can-extreme-heat-lead-to-death-91480">Health Check: how can extreme heat lead to death?</a>
</strong>
</em>
</p>
<hr>
<h2>What can you do about it?</h2>
<p>If you are feeling hot this summer and think your medicine may be contributing, it’s very important you keep taking your medicine.</p>
<p>Speak to your pharmacist or doctor about your symptoms. They will offer advice and discuss alternatives.</p><img src="https://counter.theconversation.com/content/199085/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Associate Professor Wheate in the past has received funding from the ACT Cancer Council, Tenovus Scotland, Medical Research Scotland, Scottish Crucible, and the Scottish Universities Life Sciences Alliance. He is a Fellow of the Royal Australian Chemical Institute, a member of the Australasian Pharmaceutical Science Association, and a member of the Australian Institute of Company Directors. Nial is the chief scientific officer of Vairea Skincare LLC and a Standards Australia panel member for sunscreen agents.</span></em></p><p class="fine-print"><em><span>Jessica Pace does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>If you think your medicine may be contributing to overheating, it’s very important you keep taking your medicine. Discuss your symptoms with your pharmacist or doctor.Nial Wheate, Associate Professor of the Sydney Pharmacy School, University of SydneyJessica Pace, Associate Lecturer, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1962182023-01-25T00:32:09Z2023-01-25T00:32:09Z5 reasons to check on your elderly neighbour during a heatwave<figure><img src="https://images.theconversation.com/files/500956/original/file-20221214-20-19j3u9.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1000%2C664&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/overheated-asian-senior-woman-sweatinghigh-temperature-1954041304">Shutterstock</a></span></figcaption></figure><p>We all know someone who insists on wearing a cardigan in summer or refuses to turn on the air conditioning because “it’s not that hot”. Chances are this is an older person, and there’s a good reason for that.</p>
<p>As we get older, we tend to not “feel” the heat <a href="https://www.sciencedirect.com/science/article/pii/S1568163710000450?casa_token=LxiONa0xZXQAAAAA:8IYLW0YquTHHUGkd2qiMgz6FNU3y2f4FIW96Lu9a-gjbAWw8iOgt7AOQ9C0UWMmDtXWOkqw#fig4">as much</a> even though our bodies are <a href="https://journals.physiology.org/doi/full/10.1152/japplphysiol.00202.2003">less able to handle the heat</a>. This contradiction can have <a href="https://www.sciencedirect.com/science/article/pii/S0160412017321980?casa_token=-nCG3M20MawAAAAA:VYwlO1kZIpibQnCLlm4LuSKMkK9nNvOgvdrXzUPHglOknNKp20UX0oty1DS2uWrlCZnoZhg">lethal consequences</a>, especially during periods of extreme heat.</p>
<p>So, why is extreme heat so dangerous for older people? And what can we do to help?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-how-can-extreme-heat-lead-to-death-91480">Health Check: how can extreme heat lead to death?</a>
</strong>
</em>
</p>
<hr>
<h2>Why are older people at risk?</h2>
<p><a href="https://www.sciencedirect.com/science/article/pii/S2212420921006324">Extreme heat kills</a> more Australians than <a href="https://www.sciencedirect.com/science/article/pii/S1462901114000999">all other natural hazards</a>, and people aged 60 or older account for 69% of those deaths.</p>
<p>There are five key reasons we’re more susceptible to heat as we get older.</p>
<p><strong>1. Bodily changes</strong></p>
<p>One of the main ways we lose excess heat, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3228253/">blood flowing to our skin</a>, isn’t as effective as we get older. This is in part because the blood vessels in our skin don’t expand fast enough, and we may have less blood pumping with each beat of our heart.</p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S016041202031864X#f0010">Many other changes</a> in our bodies also lead us to gain and store more heat as we get older. These include how our bodies control sweat and how well our kidneys balance fluid, which are both important for staying cool.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-rising-temperatures-affect-our-health-123016">How rising temperatures affect our health</a>
</strong>
</em>
</p>
<hr>
<p><strong>2. Social isolation</strong></p>
<p>Loneliness and social isolation are <a href="https://www.sciencedirect.com/science/article/pii/S1064748120304425">health risks</a> on their own, but also <a href="https://www.sciencedirect.com/science/article/pii/S0160412020318237#b0065">multiply the risk</a> of heat-related illness. </p>
<p>A South Australian <a href="https://www.mdpi.com/1660-4601/10/12/6721">survey</a> of older people showed those who were socially isolated were less confident in asking for help during a heatwave. </p>
<p>This is concerning as many older Australians <a href="https://www.aihw.gov.au/reports/older-people/older-australians/contents/housing-and-living-arrangements">live alone</a>, and we are more likely to live alone as we get older.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/one-in-four-australians-are-lonely-which-affects-their-physical-and-mental-health-106231">One in four Australians are lonely, which affects their physical and mental health</a>
</strong>
</em>
</p>
<hr>
<p><strong>3. Beliefs and behaviour</strong></p>
<p>Older Australians may not respond to heat in ways that protect their own health and wellbeing. Australian culture tends to view heat tolerance as a matter of <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3290974/">resilience</a> and <a href="https://www.tandfonline.com/doi/full/10.3402/gha.v5i0.19277">identity</a>, where there is a sense of generational pride in being able to cope with the heat. </p>
<p><a href="https://www.sahealth.sa.gov.au/wps/wcm/connect/c67cf100436d8e7082a2dfc9302c1003/Adaptive+capabilities+in+elderly+people+during+extreme+heat+events+in+SA+-+Public+Health+Service+-+scientific+services+20140328.pdf?MOD=AJPERES&CACHEID=ROOTWORKSPACE-c67cf100436d8e7082a2dfc9302c1003-nKKgCmQ">Reports also suggest</a> many older people have concerns about the cost of air conditioning, may be hesitant to use it, or accidentally use reverse cycle units as heaters.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/high-energy-costs-make-vulnerable-households-reluctant-to-use-air-conditioning-study-86624">High energy costs make vulnerable households reluctant to use air conditioning: study</a>
</strong>
</em>
</p>
<hr>
<p><strong>4. Medical issues</strong></p>
<p>Many chronic illnesses that are more common with age are also associated with an increased risk for heat-related illness. Because blood flow is so important for regulating our body temperature, it’s not surprising that conditions such as <a href="https://www.sciencedirect.com/science/article/pii/S1071916417300969?casa_token=LEe23NWx7V0AAAAA:-cw7TgysaYdqXq0FTuTtIxxE3Oua1NImlwmmvWWSyt39guUUWbzOsevcsoBI8tw5hbbkwaI">heart failure</a> and <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4861190/">diabetes</a> are associated with increased heat risk.</p>
<p>Similarly, many medications commonly prescribed for chronic illnesses can <a href="https://www.health.vic.gov.au/environmental-health/extreme-heat-information-for-clinicians">interfere</a> with how our body regulates temperature. For instance, some blood pressure medicines reduce our ability to sweat and lose heat.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-time-of-day-should-i-take-my-medicine-125809">What time of day should I take my medicine?</a>
</strong>
</em>
</p>
<hr>
<p><strong>5. Home environment</strong></p>
<p>It is <a href="https://www.anglicare.asn.au/wp-content/uploads/2022/09/Australia-Fair-Ageing-in-Place.pdf">increasingly difficult</a> for older Australians to find affordable and appropriate housing, especially pensioners and renters. </p>
<p>Poor home design, lack of insulation, inability to pay their energy bills, and limited income <a href="https://cur.org.au/cms/wp-content/uploads/2016/12/heatwaveshomeshealth-briefing-paper_rmit-2.pdf">all contribute</a> to being vulnerable to heatwaves in Australia. This is particularly troubling as energy prices soar.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/to-keep-heatwaves-at-bay-aged-care-residents-deserve-better-quality-homes-85174">To keep heatwaves at bay, aged care residents deserve better quality homes</a>
</strong>
</em>
</p>
<hr>
<h2>What can we do?</h2>
<p><strong>Older Australians</strong></p>
<p>Knowing the risks of extreme heat is the first step. Don’t <a href="https://www.mdpi.com/1660-4601/10/1/1">underestimate</a> your own risk during a heatwave. </p>
<p>There are many practical ways we can all keep ourselves and our homes cool, both safely and efficiently. These include:</p>
<ul>
<li>using a fan, <a href="https://theconversation.com/how-humid-is-it-3-things-to-keep-you-cool-in-a-hot-and-sticky-summer-and-3-things-that-wont-176365">which is effective</a>, especially when it’s humid, but may <a href="https://www.sciencedirect.com/science/article/pii/S0003687014001355?casa_token=NoCMHlZZ_SUAAAAA:vu-Yk1WnHpy5RsumlwQ-5_SvvuMjJLeV5Cm087QTUYKI6kLUKwjnZ1-FuATlzGDC36WyCTI">not be enough</a> when it’s very hot and dry. If you have an air conditioner, consider using it</li>
</ul>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/500965/original/file-20221214-12-u73s9p.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Know the signs of heat exhaustion and heat stroke" src="https://images.theconversation.com/files/500965/original/file-20221214-12-u73s9p.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/500965/original/file-20221214-12-u73s9p.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=846&fit=crop&dpr=1 600w, https://images.theconversation.com/files/500965/original/file-20221214-12-u73s9p.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=846&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/500965/original/file-20221214-12-u73s9p.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=846&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/500965/original/file-20221214-12-u73s9p.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1063&fit=crop&dpr=1 754w, https://images.theconversation.com/files/500965/original/file-20221214-12-u73s9p.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1063&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/500965/original/file-20221214-12-u73s9p.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1063&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Do you know the signs of heat-related illness?</span>
<span class="attribution"><a class="source" href="https://www.sahealth.sa.gov.au/wps/wcm/connect/6023f98b-bdcf-416b-9d3a-cfff9ea728c8/A4+Poster+-+Signs+and+symptoms+of+heat+illness.pdf?MOD=AJPERES&amp;CACHEID=ROOTWORKSPACE-6023f98b-bdcf-416b-9d3a-cfff9ea728c8-nwMnDGl">SA Health</a></span>
</figcaption>
</figure>
<ul>
<li><p>knowing the conditions inside your home by installing thermometers that ideally also <a href="https://theconversation.com/how-humid-is-it-3-things-to-keep-you-cool-in-a-hot-and-sticky-summer-and-3-things-that-wont-176365">measure humidity</a> so you know which ways will work best to cool down</p></li>
<li><p>opening windows facing away from the sun when it’s cooler outside; otherwise keep blinds closed in the heat of the day</p></li>
<li><p>taking cool showers or applying a damp cloth to the back of your neck can help cool the skin</p></li>
<li><p>taking regular, small drinks of water, even when you’re not thirsty (unless you have <a href="https://www.betterhealth.vic.gov.au/health/healthyliving/heat-stress-and-older-people#how-to-help-an-older-relative-or-friend">heart or kidney problems</a> in which case you need to talk to your doctor first as too much water may be a problem for you)</p></li>
<li><p><a href="https://www.sahealth.sa.gov.au/wps/wcm/connect/6023f98b-bdcf-416b-9d3a-cfff9ea728c8/A4+Poster+-+Signs+and+symptoms+of+heat+illness.pdf?MOD=AJPERES&CACHEID=ROOTWORKSPACE-6023f98b-bdcf-416b-9d3a-cfff9ea728c8-nwMnDGl">knowing the signs</a> of heat exhaustion and heat stroke.</p></li>
</ul>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-to-cope-with-extreme-heat-days-without-racking-up-the-aircon-bills-128857">How to cope with extreme heat days without racking up the aircon bills</a>
</strong>
</em>
</p>
<hr>
<p><strong>Older relatives, friends and neighbours</strong></p>
<p>We can all keep an eye on our older relatives, friends and neighbours as:</p>
<ul>
<li><p>keeping in touch is <a href="https://link.springer.com/article/10.17269/s41997-020-00309-2">great protection</a> from heat-related illness; check in regularly</p></li>
<li><p>when an older person can’t keep the house cool, support a day trip to a cooler place such as a library, cinema, or shopping centre</p></li>
<li><p>encourage them to talk to their doctor about how medical conditions or medications might increase their risk to heat.</p></li>
</ul>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australias-deadliest-natural-hazard-whats-your-heatwave-plan-90165">Australia's 'deadliest natural hazard': what's your heatwave plan?</a>
</strong>
</em>
</p>
<hr>
<h2>We need to raise awareness</h2>
<p>Australians are growing complacent about the health risks of extreme heat, see heatwaves as normal and public health messages <a href="https://widgets.figshare.com/articles/7618403/embed?show_title=1">aren’t cutting through</a> any more.</p>
<p>It’s also important to remember that older people aren’t all the same, so any public health approaches to extreme heat should be tailored to <a href="https://www.sciencedirect.com/science/article/pii/S0959378010001135?casa_token=e3YcjpeKWsgAAAAA:jzFlD6Wk7dvO05YEuoteZ0jUmMVc6eJczVhLxpDcw8qrLvCoTkvo2dz_wH_puWE-frzQNx4">communities and individuals</a>. </p>
<p>One way we’re trying to help is by working directly with older people. Together, we’re <a href="https://www.griffith.edu.au/research/climate-action/climate-transitions/health/ethos-project">researching and developing a smart device</a> that makes it easier to know when your house is getting warm, and customising strategies you can use to cool down safely.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-how-do-i-tell-if-im-dehydrated-107437">Health Check: how do I tell if I'm dehydrated?</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/196218/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sarah Cunningham receives an Australian Government Research Training Program scholarship. She is affiliated with the Extreme Heat and Older Persons research group which receives funding from Wellcome. </span></em></p><p class="fine-print"><em><span>Shannon Rutherford receives funding from Wellcome</span></em></p>Extreme heat kills more Australians than any other natural hazard. Here’s why it’s important to keep an eye on older family and friends this summer.Sarah Cunningham, Doctoral Candidate in Public Health, Griffith UniversityShannon Rutherford, Associate Professor, Public Health, Griffith UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1936092022-11-07T21:58:53Z2022-11-07T21:58:53ZHow to prevent missing person incidents for seniors living with dementia<figure><img src="https://images.theconversation.com/files/493928/original/file-20221107-3609-4js0ul.jpg?ixlib=rb-1.1.0&rect=87%2C150%2C5207%2C3342&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Missing person calls involving an individual with dementia increased by between 10 and 50 per cent across all Ontario regions over the last five years.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>People living with dementia are at risk of getting lost, and <a href="https://doi.org/10.1155/2021/5572764">go missing every day in Canada</a>. For example, in July, a person living with dementia went missing and was found by the police <a href="https://www.thespec.com/news/hamilton-region/2022/07/23/man-71-with-early-onset-dementia-missing-in-east-hamilton-police.html">under a highway bridge more than 24 hours after he was last seen</a>. </p>
<p>But for some people, the outcome might be different. They might <a href="https://www.cbc.ca/news/canada/british-columbia/ioan-john-pop-missing-senior-found-dead-1.5337124">never return home</a>, or in some cases <a href="https://vancouversun.com/news/dementia-and-wandering-finding-a-way-forward">never be found</a>. </p>
<p>This is a growing problem. Today, <a href="https://www.who.int/news-room/fact-sheets/detail/dementia">over 55 million people live with dementia worldwide</a>, and this number is projected to <a href="https://doi.org/10.1016/S2468-2667(21)00249-8">triple by 2050</a>. Recent research reported that the prevalence of missing person calls involving an individual with dementia has increased <a href="https://doi.org/10.1155/2021/5572764">by between 10 and 50 per cent across all Ontario regions over the last five years</a>. </p>
<p>The risk of getting lost differs among people living with dementia based on their <a href="https://doi.org/10.1093%2Fgeroni%2Figab046.2432">individual risk factors</a>. For example, some individuals may have <a href="https://doi.org/10.1093%2Fbrain%2Fawv276">reduced processing of pain and thermoregulation</a>, which means they don’t feel the cold or heat. That <a href="https://doi.org/10.1080/13607863.2014.924091">increases the likelihood of adverse outcomes when the person goes missing</a>.</p>
<h2>Prevention strategies</h2>
<p>Prevention is fundamental and <a href="https://www.publicsafety.gc.ca/cnt/mrgnc-mngmnt/rspndng-mrgnc-vnts/nss/prev-prev-en.aspx">has the potential to save lives and decrease the risk of injuries</a> for persons living with dementia. For example, Alzheimer Scotland developed <a href="https://www.alzscot.org/purplealert">a missing person app called Purple Alert to support the safety and well-being of people living with dementia</a>. If someone with dementia goes missing in the area, the app sends an alert to community citizens who have opted in.</p>
<p>In Canada, data on missing older adults living with dementia are sparse, and information on reported incidents typically comes from news and media reports. Japan is the only country we know of that keeps annual statistics regarding the number of cases of missing adults with dementia. In 2021, <a href="https://www.nippon.com/en/news/yjj2022062300331/">17,636 persons living with dementia went missing in Japan</a>.</p>
<p>It is clear that as a country, Canada needs better approaches to manage and prevent missing incidents involving people living with dementia. For example, prevention strategies could include: </p>
<ol>
<li><p><a href="https://alzheimer.ca/sites/default/files/documents/First-Responder-Handbook-Alzheimer-Society.pdf">Specialized training of first responders</a> to identify and intervene when they see a missing person with dementia. </p></li>
<li><p><a href="https://www.alz.org/help-support/caregiving/stages-behaviors/wandering">Prevention measures at home</a> and in the community. This may include providing safe common areas at home such as a fenced patio, labelling doors to provide a reminder of what each room is for, having a recent photo of the individual, and becoming familiar with the neighbourhood, including likely places a person might wander to and any hazards such as ponds and busy roads.</p></li>
<li><p>Technology to support persons living with dementia and their caregivers. For example, <a href="http://canadiansafewandering.ca/">tools to assess individual risk for going missing and getting lost</a>.</p></li>
</ol>
<h2>Sharing data</h2>
<figure class="align-center ">
<img alt="A multi-ethnic group of senior adults are walking together on a trail through the park." src="https://images.theconversation.com/files/493197/original/file-20221103-13-32d08n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/493197/original/file-20221103-13-32d08n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/493197/original/file-20221103-13-32d08n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/493197/original/file-20221103-13-32d08n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/493197/original/file-20221103-13-32d08n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/493197/original/file-20221103-13-32d08n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/493197/original/file-20221103-13-32d08n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The risk of getting lost differs among people living with dementia based on their individual risk factors.</span>
<span class="attribution"><span class="source">(FatCamera/istockphoto)</span></span>
</figcaption>
</figure>
<p>Finally, Canada needs a national strategy for collecting data on incidents of missing people living with dementia. This could optimize time and resources spent on police and search and rescue efforts, and enhance the chances of saving the lives of those who go missing. </p>
<p>The integration of multiple data sources such as health care, social programs, police and other first responders, and volunteer search and rescue organizations is key to sustain preventive efforts and proactively identify risk in the community. Currently, <a href="https://doi.org/10.1177/08404704221106156">databases on missing incidents involving people living with dementia are managed in silos</a>.</p>
<p>Researchers at the University of Waterloo are leading an <a href="https://www.canada.ca/en/public-safety-canada/news/2022/06/government-of-canada-announces-21-million-to-enhance-search-and-rescue-capabilities-for-people-living-with-dementia.html">initiative to enhance search and rescue capabilities for people living with dementia</a>. This project includes <a href="https://uwaterloo.ca/managing-risks-of-disappearance-in-persons-living-with-dementia/">engagement with multiple partners across Canada</a>, such as <a href="https://youtu.be/XWK5_LMTPbo">police and community organizations, search and rescue, and people living with dementia</a>. The project includes collaboration with <a href="https://uwaterloo.ca/managing-risks-of-disappearance-in-persons-living-with-dementia/blog/dementia-friendly-first-responder-resource-meeting">First Nations communities</a> and first responders, such as firefighters, paramedics and peacekeepers, embedded in these communities.</p>
<p>The need for these resources is growing. By 2050, <a href="https://alzheimer.ca/en/research/reports-dementia/landmark-study-report-1-path-forward">more than 1.7 million Canadians are expected to be living with dementia, with an average of 685 individuals being diagnosed each day</a>. With an increasing number of people living with dementia worldwide and in Canada, it’s crucial to find ways to promote community awareness and prevent people with dementia from getting lost.</p><img src="https://counter.theconversation.com/content/193609/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hector Perez has received funding from AGE-WELL NCE and currently receives funding from the Games Institute at the University of Waterloo.</span></em></p><p class="fine-print"><em><span>Lili Liu receives funding from Public Safety Canada, AGE-WELL NCE, and University of Waterloo Games Institute.</span></em></p>With an increasing number of people living with dementia worldwide and in Canada, it’s crucial to find ways to promote community awareness and prevent people with dementia from getting lost.Hector Perez, Postdoctoral Fellow, School of Public Health Sciences, Faculty of Health, University of WaterlooLili Liu, Professor, School of Public Health Sciences and Dean, Faculty of Health, University of WaterlooLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1842362022-06-02T01:52:03Z2022-06-02T01:52:03ZWhy do I need to pee more in the cold?<figure><img src="https://images.theconversation.com/files/466532/original/file-20220601-49081-pmkbqo.jpg?ixlib=rb-1.1.0&rect=0%2C4%2C1000%2C658&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/male-female-distress-having-go-restroom-1882909777">Shutterstock</a></span></figcaption></figure><p>You’re taking a stroll through the park on a cold winter’s morning, when it hits you – the need to find a bathroom, and quick! This didn’t used to happen in summer.</p>
<p>Is there something about winter that makes us need to pee more?</p>
<p>We study the bladder and lower urinary tract. Here are two main explanations for what’s going on.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-are-my-hands-and-feet-always-cold-and-when-should-i-be-worried-184154">Why are my hands and feet always cold? And when should I be worried?</a>
</strong>
</em>
</p>
<hr>
<h2>1. Our lifestyle changes</h2>
<p>In summer, we tend to be outside and more active. We sweat more (to lose heat) and it’s easy to become dehydrated if we don’t drink enough water.</p>
<p>This impacts the amount of free fluid our body is willing to <a href="https://www.nature.com/articles/ejcn2015233">excrete</a>, and our urine volume is often reduced because of this.</p>
<p>In winter, we’re often indoors, around water sources, so we are more likely to be hydrated, less active, and to sweat less. As such, we tend to have more free fluid to excrete via our urine.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-if-our-bodies-are-happy-at-37-why-do-we-feel-so-unhappy-when-its-too-hot-outside-159134">Curious Kids: if our bodies are happy at 37℃, why do we feel so unhappy when it's too hot outside?</a>
</strong>
</em>
</p>
<hr>
<h2>2. Our body wants to avoid losing too much heat</h2>
<p>If we become cold very quickly, the body protects our internal organs in a number of ways.</p>
<p>One is “<a href="https://pubmed.ncbi.nlm.nih.gov/4655205/">cold-induced diuresis</a>”, or an increase in urine excretion in response to the <a href="https://journals.physiology.org/doi/abs/10.1152/ajpregu.1993.264.3.R524">cold</a>.</p>
<p>Initially, blood is diverted away from the skin to avoid losing its heat to the outside air. This means more blood ends up flushing through your internal organs.</p>
<p>In particular, blood rushes to your kidneys in a greater volume and at a higher pressure. This increases the amount the kidneys need to <a href="https://journals.physiology.org/doi/full/10.1152/ajprenal.00430.2005">filter</a>. As a result, your rate of <a href="https://www.frontiersin.org/articles/10.3389/fphys.2022.841181/full">urine excretion</a> increases.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-is-it-so-cold-right-now-and-how-long-will-it-last-a-climate-scientist-explains-184155">Why is it so cold right now? And how long will it last? A climate scientist explains</a>
</strong>
</em>
</p>
<hr>
<h2>What should I do?</h2>
<p>Our diet, age, blood pressure, and personal situation can all impact how much we urinate.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/blVmyrBPves?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Could you have a small bladder? Or an overactive bladder?</span></figcaption>
</figure>
<p>Producing more urine can also be a sign of <a href="https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-201X.1998.0314f.x">hypothermia</a>. This is your body responding to the cold as a stressor, so act quickly. Find somewhere away from the cold, and slowly warm up your body. </p>
<p>If the increased urine is also accompanied by <a href="https://www.healthdirect.gov.au/hypothermia">other symptoms</a>, such as extensive shivering, breathing difficulties, or confusion, seek medical attention immediately.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-why-do-some-people-feel-the-cold-more-than-others-37805">Health Check: why do some people feel the cold more than others?</a>
</strong>
</em>
</p>
<hr>
<h2>Keep up the fluids in winter too</h2>
<p>If you’re out in the cold, you may not feel thirsty. Nonetheless, be sure to drink plenty of fluids during the day. Although it may be tempting to avoid drinking so you don’t need to keep rushing to the bathroom, this can lead to dehydration.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/466716/original/file-20220602-18-4l0pci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Smiling woman wearing yellow puffer jacket holding water bottle" src="https://images.theconversation.com/files/466716/original/file-20220602-18-4l0pci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/466716/original/file-20220602-18-4l0pci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466716/original/file-20220602-18-4l0pci.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466716/original/file-20220602-18-4l0pci.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466716/original/file-20220602-18-4l0pci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466716/original/file-20220602-18-4l0pci.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466716/original/file-20220602-18-4l0pci.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Keep drinking fluids, even in winter.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-hispanic-girl-smiling-happy-drinking-2053295111">Shutterstock</a></span>
</figcaption>
</figure>
<p>If you’re often out in the cold in light gear, and you find this increases your urinary output, there can be impacts over the long term.</p>
<p>Frequent urination can be <a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/osmotic-diuresis">detrimental</a> to your body’s natural salt balance (particularly sodium and <a href="https://www.mayoclinic.org/symptoms/low-potassium/basics/causes/sym-20050632">potassium</a>). So be sure to maintain a healthy diet.</p>
<p>It does seem like a bit of a balancing game. The key, however, is to avoid stressing your body this way when it’s cold. To do this, be sure to dress appropriately and keep warm.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/forget-heatwaves-our-cold-houses-are-much-more-likely-to-kill-us-83030">Forget heatwaves, our cold houses are much more likely to kill us</a>
</strong>
</em>
</p>
<hr>
<h2>What if you don’t notice a difference?</h2>
<p>Although the body has mechanisms to make you <a href="https://pubmed.ncbi.nlm.nih.gov/7330607/">urinate more</a> in the cold, not everyone notices peeing more in winter.</p>
<p>If you keep warm, there’s no reason to think your body would often be “shocked” into responding to cold temperatures.</p>
<p>In fact, when tracked in research studies, it has been common for researchers to record no difference in <a href="https://pubmed.ncbi.nlm.nih.gov/7330607/">urinary</a> <a href="https://pubmed.ncbi.nlm.nih.gov/1172/">output</a> between the <a href="https://pubmed.ncbi.nlm.nih.gov/29757578/">seasons</a>.</p>
<h2>What about the urine?</h2>
<p>It’s not just the volume of urine that might be different in winter. The composition can change too.</p>
<p>The body excretes a higher amount of <a href="https://pubmed.ncbi.nlm.nih.gov/29757578/">calcium</a> in the urine during <a href="https://pubmed.ncbi.nlm.nih.gov/7106963/">winter</a>.</p>
<p>This is more likely due to lifestyle during cold seasons rather than anything internal. We tend to be <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2800047/">less active</a> in winter, gain <a href="https://pubmed.ncbi.nlm.nih.gov/31093925/">extra weight</a>, and eat more salty, preserved and processed foods.</p>
<p>This means there can be a higher risk of developing <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6237522/">kidney stones</a> during winter for people who are susceptible.</p>
<p>So as the weather cools down, be sure to maintain a healthy lifestyle, stay warm, and don’t forget to stay hydrated, even when it’s cold.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-is-urine-yellow-117747">Curious Kids: why is urine yellow?</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/184236/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>No, you’re not imagining it. You can pee more in winter. Mostly, there’s nothing to worry about. But it could be a sign of hypothermia.Christian Moro, Associate Professor of Science & Medicine, Bond UniversityCharlotte Phelps, PhD Student, Bond UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1763652022-02-16T01:09:01Z2022-02-16T01:09:01ZHow humid is it? 3 things to keep you cool in a hot and sticky summer (and 3 things that won’t)<figure><img src="https://images.theconversation.com/files/445592/original/file-20220210-24693-kz2jtl.jpg?ixlib=rb-1.1.0&rect=1%2C0%2C997%2C663&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/portrait-woman-front-fan-suffering-heat-1745759825">Shutterstock</a></span></figcaption></figure><p><a href="http://www.bom.gov.au/climate/updates/articles/a020.shtml">La Niña</a> has resulted in <a href="https://www.smh.com.au/environment/weather/sydney-smashes-january-humidity-records-as-la-nina-nears-its-peak-20220118-p59p3m.html">a humid summer</a> for much of eastern Australia.</p>
<p>This climate pattern typically causes warm, humid air to rise from the western Pacific Ocean, ultimately leading to greater cloud formation, increased rainfall, and higher humidity along Australia’s eastern seaboard and tropical north.</p>
<p>So what’s the best way to cope with what’s left of a hot and humid La Niña summer?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/back-so-soon-la-nina-heres-why-were-copping-two-soggy-summers-in-a-row-173684">Back so soon, La Niña? Here's why we're copping two soggy summers in a row</a>
</strong>
</em>
</p>
<hr>
<h2>In praise of sweat (and evaporation)</h2>
<p>Sweating (and the heat loss that goes with it) is by far the most effective way our bodies use to cool us down. But it’s not sweating <em>alone</em> that does the trick. It’s the evaporation of sweat that is key.</p>
<p>For every gram of sweat you evaporate, a little over <a href="https://journals.physiology.org/doi/abs/10.1152/jappl.1972.32.4.456">2.4 kilojoules</a> of heat energy is taken with it.</p>
<p>That’s a bit difficult to visualise. So let’s think of it in terms of boiling water.</p>
<p>Evaporating roughly 140 grams of sweat results in enough energy (heat) “loss” to bring a litre of 20°C water to boiling point (at sea level).</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1487831263931088897"}"></div></p>
<p>We were treated to some interesting facts during this year’s notoriously sweaty Australian Open tennis tournament.</p>
<p>Champion player Rafael Nadal was reported to have evaporated <a href="https://www.theguardian.com/sport/2022/jan/28/tug-tuck-wipe-repeat-nadals-rituals-help-defy-his-breaking-body">over 4 kilograms of sweat</a> during his <a href="https://ausopen.com/match/2022-denis-shapovalov-vs-rafael-nadal-ms502">4 hour 8 minute quarter-final win</a> over Denis Shapovalov.</p>
<p>That’s the equivalent of brewing a 250 millilitre cup of tea via the energy of his own sweat-liberated-heat – every 2.2 minutes of the match.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-how-to-exercise-safely-in-the-heat-37286">Health Check: how to exercise safely in the heat</a>
</strong>
</em>
</p>
<hr>
<h2>So how is this all related to humidity?</h2>
<p>Sweat evaporation is dictated primarily by the wetness of the skin, and the absolute humidity of the air. <a href="https://www.weather.gov/lmk/humidity">Absolute humidity</a> is a function of the amount of water vapour in the air. </p>
<p>This is not to be confused with <a href="http://www.bom.gov.au/watl/humidity/">relative humidity</a> which is the term usually used in weather reports. This tells us how much water vapour the air is holding (as a percentage) relative to how much it could possibly hold, which goes up with temperature.</p>
<p>The bigger the difference between the wetness of the skin and the absolute humidity, the more readily sweat evaporates.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-do-i-sweat-so-much-131135">Why do I sweat so much?</a>
</strong>
</em>
</p>
<hr>
<p>In arid climates, such as central Australia, where the absolute humidity is low, sweat evaporates so rapidly you can barely feel it on your skin.</p>
<p>Whereas in humid conditions, such as in northern Australia and more recently much of eastern Australia, sweat evaporation is hindered. </p>
<p>This is why on humid days we think we’re much sweatier, when in reality we may not be sweating that much more than any other warm day. It’s just more sweat is staying on our skin (rather than evaporating), forming patches on our clothes and making us feel sticky.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Man sweating in blue shirt" src="https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Hot and sticky with all this humidity?</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/man-hyperhidrosis-sweating-very-badly-under-767078800">Shutterstock</a></span>
</figcaption>
</figure>
<h2>What can we do about it?</h2>
<p>These three simple strategies will actually keep you cool on a humid day (without aircon):</p>
<p><strong>1. Use a fan</strong></p>
<p>Use a fan to <a href="https://jamanetwork.com/journals/jama/article-abstract/2110959">increase air flow</a> and accelerate sweat evaporation. These tend to work <a href="https://www.sciencedirect.com/science/article/pii/S2542519621001364">to at least 39°C</a>.</p>
<p>Misting fans <a href="https://www.sciencedirect.com/science/article/pii/S1440244021001092?casa_token=VfKIET08fTEAAAAA:2n8OqjI1xPzZB-ASMkeyIhrZplzkjItRSooTTT1OdrewatuuDbDiDzwYDiRCBYO5anHUyvBnKg">also work</a> well as water settles on the skin and subsequently evaporates, taking body heat with it. Alternatively, you can spray your skin with water and <a href="https://www.sciencedirect.com/science/article/pii/S0048969720347094">sit in front of a fan</a>.</p>
<p><strong>2. Use ‘ice towels’</strong></p>
<p>Wrap <a href="https://journals.lww.com/acsm-msse/fulltext/2017/05000/In_Play_Cooling_Interventions_for_Simulated.16.aspx">crushed ice in a damp towel</a> and wrap it around your neck. Professional tennis players regularly do this to keep cool. This circumvents the need for evaporation by taking heat straight from the body via conduction.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1476878329516937218"}"></div></p>
<p><strong>3. Wet your clothes</strong> </p>
<p>Soaking your t-shirt with water and putting it back on <a href="https://journals.physiology.org/doi/full/10.1152/japplphysiol.00786.2019">reduces the increase in core temperature</a> the same way as the evaporation of sweat. But it has the added bonus of not dehydrating the body. Alternatively, directly wetting the skin with a spray or wet sponge provides <a href="https://jamanetwork.com/journals/jama/article-abstract/2752456">the same benefit</a>.</p>
<h2>What won’t work</h2>
<p>Here are three strategies commonly recommended for beating the heat that won’t always work.</p>
<p><strong>1. Evaporative cooling</strong></p>
<p><a href="https://www.choice.com.au/home-and-living/cooling/air-conditioners/articles/evaporative-cooler-vs-air-conditioner">Evaporative coolers</a> work by passing hot air across a wet membrane to cool it. These work really well on hot, dry days. But on humid days, the air can hold less extra water, so evaporation is reduced and therefore, air is cooled far less.</p>
<p><strong>2. Drinking chilled drinks</strong></p>
<p>Although cold drinks may feel like they cool you down, it is mainly in your mind. Your body warms up the cold fluids or ice. At the same time, this triggers a <a href="https://journals.physiology.org/doi/full/10.1152/japplphysiol.01059.2013">reduction in sweating</a>, which reduces the amount of heat you lose via evaporation. One cancels out the other.</p>
<p>This results in the <a href="https://link.springer.com/article/10.1007/s40279-017-0842-8?platform=hootsuite_1&error=cookies_not_supported&code=890690fa-dc5b-493a-8ad7-9ccef673e811">same body temperature</a> irrespective of how cold (or hot) the drink is.</p>
<p>We’re not suggesting abandoning drinks altogether. In fact, you do need to replenish water that you sweat, to avoid dehydration. But don’t expect cold drinks to perform any better than warm ones. Just drink fluid at the temperature you find most palatable.</p>
<p>Similarly, eating cold food, such as ice cream or other frozen or chilled snacks, does not result in any net cooling effect. By all means, eat them if they make you feel better, but don’t expect them to actually cool you down.</p>
<p><strong>3. Sunscreen</strong></p>
<p>While it is very important to protect you skin from UV, there is no evidence wearing sunscreen makes any difference to how hot you get or how hot you feel.</p><img src="https://counter.theconversation.com/content/176365/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ollie Jay receives funding from National Health and Medical Research Council (NHMRC), Wellcome Trust (UK), MS Research Australia, NSW Dept of Industry and Environment, Tennis Australia, Cricket Australia, National Rugby League (NRL). He also serves as a consultant on research projects for the National Institutes of Health and US Dept of Defence. He served on Board of Trustees for the American College of Sports Medicine (ACSM) from 2018-21</span></em></p><p class="fine-print"><em><span>Connor Graham does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>On a hot and humid day, the fan is your friend. But ice cream won’t make the difference you think it will.Connor Graham, Research Fellow, Thermal Ergonomics Laboratory, University of SydneyOllie Jay, Professor of Heat & Health; Director of Heat & Health Research Incubator; Director of Thermal Ergonomics Laboratory, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1646882021-07-21T12:26:07Z2021-07-21T12:26:07ZHeat stroke is a danger, but cardiovascular stress causes more heat wave deaths<figure><img src="https://images.theconversation.com/files/411997/original/file-20210719-15-rxda7x.JPG?ixlib=rb-1.1.0&rect=101%2C173%2C3676%2C2071&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A Salvation Army emergency vehicle is set up as a cooling station during a heatwave in Calgary, Alta. on June 30. </span> <span class="attribution"><span class="source">THE CANADIAN PRESS/Jeff McIntosh</span></span></figcaption></figure><p>Every summer we invariably deal with at least one heat wave. With global warming, they are becoming <a href="https://climateatlas.ca/map/canada/hwnum_2030_45#z=4&lat=48.84&lng=-90.26">longer, more intense and more frequent</a>. Heat waves are now among the most dangerous global natural hazards we face, accounting for more fatalities on average than any other extreme weather event, according to the <a href="https://www.weather.gov/hazstat/">United States National Weather Service</a>. </p>
<p>Canada is not immune, as evidenced by the recent heat wave across the Pacific Northwest that included a <a href="https://www.cbc.ca/news/canada/british-columbia/bc-alberta-heat-wave-heat-dome-temperature-records-1.6084203">Canadian record-breaking temperature of nearly 50 C</a> in Lytton, B.C. near the end of June. During the week of the heat wave, the province had <a href="https://www2.gov.bc.ca/assets/gov/birth-adoption-death-marriage-and-divorce/deaths/coroners-service/news/bccs-chief-coroner-updated-statement2.pdf">tripled the number of reported deaths</a> that normally occur during that period. </p>
<p>While the sharp rise in mortality rate during a heat wave is apparent, the cause of those deaths may not always be. Heat stroke is not the only issue. The biggest factor is the stress that extreme heat places on the cardiovascular system (the heart and blood vessels).</p>
<h2>Heat stroke</h2>
<p>Heat stroke, perhaps the most obvious consequence of a heat wave, is the progression of <a href="https://www.mayoclinic.org/diseases-conditions/heat-exhaustion/symptoms-causes/syc-20373250">heat exhaustion</a>, a milder condition that causes symptoms such as heavy sweating, clammy skin, fatigue, feeling faint or dizzy, nausea and headache. </p>
<p><a href="http://doi.org/10.1056/NEJMra1810762">Heat stroke</a> is serious and can be life-threatening. It is subclassified as either classic (occurring when someone is at rest) or exertional (occurring through strenuous physical activity). Both forms result in a series of reactions that cause excessive inflammation, leading to central nervous system dysfunction (confusion, seizures or loss of consciousness) and multiple organ failure.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/412000/original/file-20210719-19-a0839w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A man walking on a park path with the Calgary skyline in the distance, with a haze of smoke" src="https://images.theconversation.com/files/412000/original/file-20210719-19-a0839w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412000/original/file-20210719-19-a0839w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412000/original/file-20210719-19-a0839w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412000/original/file-20210719-19-a0839w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412000/original/file-20210719-19-a0839w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412000/original/file-20210719-19-a0839w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412000/original/file-20210719-19-a0839w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Following the western heat wave, a haze of wildfire smoke from British Columbia hangs over downtown Calgary in July 2021.</span>
<span class="attribution"><span class="source">THE CANADIAN PRESS/Jeff McIntosh</span></span>
</figcaption>
</figure>
<p>In classic heat stroke, it is poor heat-dissipating mechanisms or simply excessive heat exposure that is the culprit. With exertional heat stroke, it is the excessive metabolic heat during exercise that exceeds the body’s ability to maintain its temperature through heat-loss mechanisms like sweating. The common characteristic of both forms is a core temperature exceeding 40.5C (normal is 37C). </p>
<p>While heat stroke during a heat wave is certainly a risk, it alone provides a narrow scope of the true health impact. Most often, excess mortality during a heat wave is actually a result of increased cardiovascular burden and amplification of existing health conditions.</p>
<h2>Cardiovascular burden of heat</h2>
<p>When core and skin temperature rise, thermosensors across the body respond by shunting a large proportion of blood to the periphery (skin). This has two primary effects: </p>
<ol>
<li>It increases the skin blood flow allowing an increased sweat rate, and in turn, heat loss via evaporation.</li>
<li>It increases the skin temperature to enable more heat transfer from the body to the environment (heat loss primarily via convection).</li>
</ol>
<p>This process of increasing blood flow to the skin to regulate body temperature (thermoregulation) is taxing on the cardiovascular system. The blood vessels near the skin need to dilate, and the heart needs to pump harder and faster. </p>
<p>That is where the major problem lies: A large fraction of the population has some form of cardiovascular disease. Nearly 10 per cent of Canadian adults suffer from <a href="https://www.canada.ca/en/public-health/services/publications/diseases-conditions/report-heart-disease-Canada-2018.html">heart disease</a>, and nearly two-thirds of Canadians are prone to impaired heart and metabolic function <a href="https://www150.statcan.gc.ca/n1/pub/82-625-x/2019001/article/00005-eng.htm">by being overweight</a>. Not surprisingly, <a href="https://dx.doi.org/10.1249%2FMSS.0000000000000325">rates of cardiovascular events are notably increased</a> during a heat wave.</p>
<h2>Populations at risk</h2>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/411998/original/file-20210719-15-1n6mvpx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A boy running through a fountain" src="https://images.theconversation.com/files/411998/original/file-20210719-15-1n6mvpx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/411998/original/file-20210719-15-1n6mvpx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/411998/original/file-20210719-15-1n6mvpx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/411998/original/file-20210719-15-1n6mvpx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/411998/original/file-20210719-15-1n6mvpx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/411998/original/file-20210719-15-1n6mvpx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/411998/original/file-20210719-15-1n6mvpx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Children are at risk for heat stroke because of their small size and immature thermoregulation system.</span>
<span class="attribution"><span class="source">THE CANADIAN PRESS/Jeff McIntosh</span></span>
</figcaption>
</figure>
<p>Invariably those who cannot escape the heat, namely outdoor workers and those with poor access to air-conditioning, are most at risk. Young children are also at risk because of their small body size and underdeveloped thermoregulatory system. However, advanced aging and cadiovascular disease is proving to be the biggest factor.</p>
<ul>
<li><p><strong>The elderly</strong>: Advanced aging is associated with a reduced capacity to thermoregulate, primarily attributable to a progressively compromised cardiovascular system. Interestingly, <a href="https://dx.doi.org/10.1080%2F23328940.2017.1379585">behavioral thermoregulation</a> — which includes actions like seeking shade or air conditioning — is also compromised in the elderly, such that cooling strategies are sought out less frequently compared to young adults.</p></li>
<li><p><strong>Disease</strong>: Pre-existing conditions — particularly those involving the cardiovascular system, such as heart disease and diabetes — dramatically increase the risk of heat-related illness. Often, <a href="https://doi.org/10.1111/jcpt.12294">many medications</a> used to treat these diseases can further interfere with the thermoregulatory responses to heat (for example, beta-blockers used to treat high blood pressure can inhibit the heart rate response, and diuretics can exacerbate dehydration).</p></li>
</ul>
<h2>Reducing the risk</h2>
<figure class="align-center ">
<img alt="A sign for an emergency cooling centre in Toronto" src="https://images.theconversation.com/files/411999/original/file-20210719-23-1qqvyj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/411999/original/file-20210719-23-1qqvyj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=427&fit=crop&dpr=1 600w, https://images.theconversation.com/files/411999/original/file-20210719-23-1qqvyj.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=427&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/411999/original/file-20210719-23-1qqvyj.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=427&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/411999/original/file-20210719-23-1qqvyj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=537&fit=crop&dpr=1 754w, https://images.theconversation.com/files/411999/original/file-20210719-23-1qqvyj.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=537&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/411999/original/file-20210719-23-1qqvyj.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=537&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Seeking relief from the heat is one way to help prevent heat stroke.</span>
<span class="attribution"><span class="source">THE CANADIAN PRESS/Frank Gunn</span></span>
</figcaption>
</figure>
<p>The primary prevention of heat illness is through immediate behaviour. Seeking air-conditioned environments, <a href="https://doi.org/10.1016/j.apergo.2014.07.013">increasing air flow through electric fans</a>, wearing light, breathable and loose-fitting clothing, keeping hydrated and avoiding strenuous activities (especially in the sun) should be the first line of defence, particularly in vulnerable populations. </p>
<p>However, assuring that the cardiovascular system is ready to take on the heat will be an integral step in curtailing the rates of heat illness. If daily exercise is not an option (or too difficult), an alternative may be to safely fight fire with fire — that is, through <a href="https://doi.org/10.1152/japplphysiol.00141.2020">heat therapy</a>. </p>
<p>Supervised heat therapy is emerging as a therapeutic tool for cardiovascular disease by improving heart and blood vessel function. It may also lead to moderate <a href="https://doi.org/10.1111/sms.12408">heat acclimation</a>, which can make it easier to deal with the heat by improving the body’s thermoregulatory response system. </p>
<p>In the end, exercise, a healthy diet, and perhaps also heat therapy (if done safely) will not only reduce the incidence for the leading cause of death worldwide (heart disease), it will also reduce the excess deaths during a heat wave. </p>
<p>Indeed, excess mortality during a heat wave is only marginally explained by incidences of outright heat stroke. Most often it is secondary from the increased cardiovascular burden associated with thermoregulatory responses to the heat.</p><img src="https://counter.theconversation.com/content/164688/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Anthony Bain does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Heat stroke is a danger in extreme temperatures, but a major risk factor for dying during a heat wave is cardiovascular disease and other pre-existing health conditions.Anthony Bain, Assistant Professor, Kinesiology, University of WindsorLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1591342021-05-28T02:01:25Z2021-05-28T02:01:25ZCurious Kids: if our bodies are happy at 37°C, why do we feel so unhappy when it’s too hot outside?<figure><img src="https://images.theconversation.com/files/402790/original/file-20210526-17-1rc9z1l.jpg?ixlib=rb-1.1.0&rect=1%2C4%2C997%2C660&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/boy-splash-water-hot-summer-day-212230843">from www.shutterstock.com</a></span></figcaption></figure><blockquote>
<p>How come the inside of your body is happy at 37 degrees but when the outside temperature is 37 degrees your body is very unhappy? — Patrick, aged 8. </p>
</blockquote>
<p>Great question, Patrick!</p>
<p>You’re right. Most people’s bodies are happiest when their inside temperature sits around a nice <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6946399/">36.5-37.5°C</a>. These temperatures allow your body to work the best.</p>
<p>But your body temperature does go through small changes. It can be a bit lower when you’re <a href="https://jphysiolanthropol.biomedcentral.com/articles/10.1186/1880-6805-31-14">asleep</a>. It can also change during the day when you feel hungry, tired or cold. And when you’re sick, your <a href="https://youtu.be/BxgEoLmOACo">temperature can rise</a>. That’s when you might have a <a href="https://youtu.be/jRvxnpfCDSo">fever</a>.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-are-our-top-eyelashes-longer-than-our-bottom-eyelashes-132585">Curious Kids: why are our top eyelashes longer than our bottom eyelashes?</a>
</strong>
</em>
</p>
<hr>
<h2>A happy body</h2>
<p>It’s really important to keep your body temperature at around 37°C otherwise you can overheat and get quite <a href="https://www.sciencedirect.com/science/article/pii/S1566070216300017">sick</a>.</p>
<p>To do this, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4854186/">muscles</a>, such as the ones in your arms and legs, tighten (or contract). This process generates, or “makes”, heat. Your blood then <a href="https://physoc.onlinelibrary.wiley.com/doi/10.1113/jphysiol.2002.035089">carries</a> this heat around your body.</p>
<p>But to stop your inside temperature getting too high, for example when you’re exercising on a hot day, your body needs to lose some of that heat.</p>
<figure class="align-center ">
<img alt="A young girl running in the park." src="https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Running generates a lot of heat, which our body needs to get rid of to the air around us.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Warm blood travels through <a href="https://www.ncbi.nlm.nih.gov/books/NBK507838/">blood vessels</a> close to your skin. This heat is then “lost” to the air around you.</p>
<p>If that’s not enough to cool you down, your body will also start sweating. This speeds up how you lose heat through your skin.</p>
<p>You usually feel the most comfortable when it’s around <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5961609/">18-24°C</a>. This seems to be a nice temperature that allows any extra heat to escape into the air. But it’s also not so cold that you <a href="https://open.oregonstate.education/aandp/chapter/24-6-energy-and-heat-balance/">need to move around</a> to keep warm.</p>
<h2>Phew, it’s stinking hot!</h2>
<p>Things that get in the way of losing heat through the skin can make you feel hot, such as wearing a woolly jumper in summer.</p>
<p>But you can also feel uncomfortable on a hot and humid day. That’s because the warm outside temperature makes it hard for you to lose heat from your skin to the air around you (because the air is already quite warm). And without a breeze, it’s even harder for the heat to be carried away.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-do-scabs-form-151586">Curious Kids: how do scabs form?</a>
</strong>
</em>
</p>
<hr>
<h2>How to keep cool</h2>
<p>If it’s very hot or humid, your body may find it hard to lose extra heat. So to keep cool on these days:</p>
<ul>
<li><p>drink water often. This not only keeps your body happy, it gives you extra liquid to turn into sweat. Sweating helps you lose heat</p></li>
<li><p>avoid direct sunlight, and try to keep to the shade or places with a cool breeze</p></li>
<li><p>wear thin clothing and natural fibres, which can allow a clear flow of air</p></li>
<li><p>wear light-coloured clothing, as this can keep you cooler than darker colours</p></li>
<li><p>avoid running, jumping or riding your bike in the middle of the day</p></li>
<li><p>on hot days, jump in a pool, or try to escape the heat by putting on the air-conditioning inside</p></li>
<li><p>sit in front of a fan. This breeze carries heat away from your skin and into the air around you, cooling you down quickly.</p></li>
</ul>
<hr>
<p><em>Hello, Curious Kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au</em></p><img src="https://counter.theconversation.com/content/159134/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>When the weather outside is very hot, it can make us feel really unhappy. Here’s why.Christian Moro, Associate Professor of Science & Medicine, Bond UniversityCharlotte Phelps, PhD Student, Bond UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1585342021-04-07T15:38:24Z2021-04-07T15:38:24ZWe discovered that whale and dolphin brains produce lots of heat. Why it matters<figure><img src="https://images.theconversation.com/files/393741/original/file-20210407-21-1m642x5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A humpback whale near the Antarctic ice.</span> <span class="attribution"><span class="source">Dr Olga Shpak </span></span></figcaption></figure><p>We have all heard the mantra that dolphins and whales (cetaceans) are highly intelligent animals. Some claim they’re on par with great apes and humans – maybe even smarter. But where does this concept come from? </p>
<p>There are two lines of thought. Firstly, a range of cetacean behaviours are <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1469-185X.2008.00049.x">interpreted</a> as displays of notable intelligence. Second, cetaceans have very <a href="https://www.karger.com/Article/Abstract/454797">large brains</a>; several species have brains that weigh more than human brains. We have large brains, and it is the structure and activity within these large brains that determines our abilities to examine, analyse and manipulate the world in a very complex way. So it has been thought that any other animal that has a brain as large, or larger, must be using their brain for the same thing. </p>
<p>But this logic is based on a very specific assumption: that 1 gram of brain tissue has, on average, the same capacity to process information in the same way irrespective of the brain in which it is found. It is this assumption that I have <a href="https://onlinelibrary.wiley.com/doi/abs/10.1017/S1464793106007019">questioned over the past 20 years</a> and I have come to a very different conclusion.</p>
<p>In my most <a href="https://www.nature.com/articles/s41598-021-84762-0">recent study</a>, my colleagues and I have ascertained that the cetacean brain is indeed special. Not for intelligence, though: it is special because it produces a lot more heat than the brains of other mammals. Through our research we’ve concluded that the cetacean brain has a specialised thermogenic system. It helps the animal’s brain to produce enough heat to maintain a functional brain temperature, and we believe this will combat the loss of heat to the water. This is separate to the special way whales and dolphins <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0116734">keep their bodies warm</a>.</p>
<p>Evidence suggests the neurothermogenic specialisation we describe evolved around 32 million years ago.</p>
<p>With this knowledge, scientists can better understand how important water temperature is to the survival of cetaceans. This, in turn, will allow us to understand what will happen to certain species of cetaceans during the <a href="https://science.sciencemag.org/content/363/6423/128.summary">inevitable rise in oceanic temperatures</a> associated with anthropogenic-induced climate change.</p>
<p>It is quite possible that some species, such as those dependent on the polar ice, like narwhals and beluga whales, may become victims of global warming. This new understanding of cetaceans will allow us to direct our conservation efforts in the most appropriate way to secure the future of as many species of cetacean as possible.</p>
<h2>Size and skill</h2>
<p>Compared to humans – and indeed many other mammals – cetacean brains have a very small <a href="https://onlinelibrary.wiley.com/doi/abs/10.1017/S1464793106007019">prefrontal cortex</a> (that part involved in our higher mental/executive activities), a tiny <a href="https://link.springer.com/article/10.1007/s00429-013-0660-1">hippocampus</a> (responsible for memory formation/retrieval and spatial navigation), and many other features that are very different to other mammals.</p>
<p>This means we can conclude that the structure of the cetacean brain does not endow them with the “hardware” necessary for the production of behaviours that are more complex than those seen in many other animals, unlike humans.</p>
<p>So, if the cetacean brain is not large for intellectual purposes, why is it so big? </p>
<p>Cetacean brains became truly large <a href="https://onlinelibrary.wiley.com/doi/abs/10.1017/S1464793106007019">around 32 million years ago</a>, about 20 million years after they became fully aquatic mammals. At this time, there was a <a href="https://science.sciencemag.org/content/292/5517/686">major cooling</a> of global oceanic temperatures. This coincided with the loss of the shallow, warm, nutrient-rich, equatorial <a href="https://www.britannica.com/topic/Neo-Tethys-Sea">Tethys sea</a>. These ancient cetaceans were faced with a quandary: adapt to this new, cold, open ocean environment, or become extinct.</p>
<p>The mammalian brain produces its own heat, independent of the body, to maintain a stable temperature of 37°C. Even a small drop in brain temperature leads to a reduction in neural activity. Cetaceans mostly live in oceanic waters; the mammalian body loses heat via conductive heat transfer to the water <a href="https://www.nature.com/articles/335675b0">90 times faster</a> than to air at the same temperatures; and mammal brains need to be maintained at 37°C. Given these factors, I proposed that perhaps the environmental pressure of colder water occurring around 32 million years ago was the trigger for the evolution of the larger brain in cetaceans.</p>
<h2>Inside the cetacean brain</h2>
<p>To provide support to this idea, my colleagues and I examined the heat-producing system within the brains of cetaceans and their close relatives the artiodactyls – such as hippopotamuses, pigs, antelopes, buffaloes and giraffes. </p>
<p>We reasoned that this heat-producing system would have to use the process of <a href="https://jeb.biologists.org/content/214/2/242">non-shivering thermogenesis</a>, a way to produce heat within cells rather than through muscular activity, as there are no muscles surrounding the brain. The most commonly studied part of the body that produces heat through non-shivering thermogenesis is <a href="https://www.mayoclinic.org/healthy-lifestyle/weight-loss/expert-answers/brown-fat/faq-20058388">brown fat</a>. Brown fat cells can change their internal metabolic pathways so as to produce heat, warming up the body. This happens when mitochondria (organelles within the cell that produce energy) change their activity so that rather than producing adenosine triphosphate (ATP), for chemical energy in the cell, they produce heat. This is achieved by activating uncoupling proteins (UCPs). </p>
<p>In the cetacean brain we found that almost three times as many neurons contain these proteins compared to their terrestrial relatives. We also found that between 30 and 70% of glial cells contain UCPs in cetaceans, while in artiodactyls the glial cells did not contain UCPs in readily detectable amounts. Glial cells are the housekeepers of the brain: they maintain the right micro-environment to support active neuronal functioning.</p>
<p>We conclude that the cetacean brain has a specialised thermogenic system that emerged around 32 million years ago. This, we believe, will combat the loss of heat to the water – and help cetaceans to maintain a functional brain temperature.</p>
<h2>A special brain</h2>
<p>So, yes: the cetacean brain is special, as long believed. But this brain isn’t used for special intellectual functions and complex thoughts. Instead, it’s special because it produces a lot more heat than the brains of other mammals, and this is necessary for their survival in the colder aquatic environment they inhabit.</p><img src="https://counter.theconversation.com/content/158534/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul Manger receives funding from the National Research Foundation of South Africa. </span></em></p>The cetacean brain has a specialised thermogenic system that helps the animal’s brain to produce enough heat to maintain a functional brain temperature.Paul Manger, Professor of Comparative and Evolutionary Neurobiology, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1311352020-02-28T03:50:44Z2020-02-28T03:50:44ZWhy do I sweat so much?<figure><img src="https://images.theconversation.com/files/317699/original/file-20200228-24685-18o54ey.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1000%2C666&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-man-horror-looking-sweaty-shirt-447385717">Shutterstock</a></span></figcaption></figure><p>If you’re hot and sticky even before your daily commute, you might ask why you sweat so much.</p>
<p>Sweating is usually the body’s way of stopping you overheating. But for some people, sweating becomes a problem. Either they sweat for no obvious reason or (as <a href="https://www.theatlantic.com/health/archive/2019/11/prince-andrew-says-he-once-didnt-sweat-is-that-possible/602227/">Prince Andrew admitted last year</a>) not at all.</p>
<p>So why do some people sweat more than others? And what can you do about excess sweating?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/anhidrosis-why-some-people-apparently-like-prince-andrew-just-cant-sweat-127280">Anhidrosis: why some people – apparently like Prince Andrew – just can't sweat</a>
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</em>
</p>
<hr>
<h2>Remind me again, why do we sweat?</h2>
<p>Humans need to regulate their internal body temperature to keep it constant, even when the environmental temperature rises, perhaps on a hot day, sitting in a hot-tub or running for the bus.</p>
<p>That’s because a rise in internal body temperature can lead to our organs overheating, fatigue, heat exhaustion and heat stroke.</p>
<p>Preventing severe heat gain requires a careful balance between the heat our body produces (from everyday metabolism), heat from the environment and the heat our body loses.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-skin-is-a-very-important-and-our-largest-organ-what-does-it-do-91515">The skin is a very important (and our largest) organ: what does it do?</a>
</strong>
</em>
</p>
<hr>
<p>Our bodies are well-designed for this. We have special temperature sensors in our skin and central nervous system (brain and spinal cord) that send signals to the body’s thermostat in the brain to alert it to increases in body temperature.</p>
<p>The body’s largest organ, the skin, is also designed to remove heat from the body. The most noticeable way is losing heat via evaporating sweat.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-happens-in-the-body-when-we-sweat-85831">Curious Kids: What happens in the body when we sweat?</a>
</strong>
</em>
</p>
<hr>
<h2>How does sweating cool us down?</h2>
<p>When our skin or core body temperature rises sufficiently, the thermostat in the brain sends impulses via our central nervous system to increase blood flow to the skin. The thermostat also activates the sweat glands. </p>
<p>Our sweat glands release droplets onto our skin that become vapour when the blood flowing through the skin passes underneath. </p>
<p>As the sweat vaporises, energy (in the form of heat) passes into the environment, cooling the blood. This cooled blood gets circulated back to the heart and brain, and cools our core body temperature.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/317694/original/file-20200227-24651-ykhocw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/317694/original/file-20200227-24651-ykhocw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/317694/original/file-20200227-24651-ykhocw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=557&fit=crop&dpr=1 600w, https://images.theconversation.com/files/317694/original/file-20200227-24651-ykhocw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=557&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/317694/original/file-20200227-24651-ykhocw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=557&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/317694/original/file-20200227-24651-ykhocw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=700&fit=crop&dpr=1 754w, https://images.theconversation.com/files/317694/original/file-20200227-24651-ykhocw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=700&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/317694/original/file-20200227-24651-ykhocw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=700&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The body loses excess heat via evaporation.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/perspiring-anatomical-human-skin-layers-cross-1067095673">from www.shutterstock.com</a></span>
</figcaption>
</figure>
<p>This is why a day in the sun can feel so draining. Your body is working much harder and using much more energy to keep you cool.</p>
<p>By preventing our organs from overheating, sweat not only keeps us healthy, it also allows us to enjoy (or tolerate) the hot Australian summer. </p>
<p>So it’s important to stay hydrated on a hot day so your body can produce and replace the volume of sweat necessary to keep you cool.</p>
<h2>OK, but why do I sweat so much?</h2>
<p>You might find yourself sweating more or less than usual for a number of reasons, other than it being a hot day.</p>
<p><strong>Exercise</strong></p>
<p>Exercise improves our ability to produce sweat and keep cool. People who exercise regularly (particularly in the heat) can <a href="https://journals.physiology.org/doi/full/10.1152/japplphysiol.00495.2010">produce more sweat</a> during exercise. This helps our bodies perform longer, with less physiological strain.</p>
<p>So many of the Australian Olympic athletes will undergo a period of heat acclimatisation in the lead up to Tokyo 2020.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-is-japans-olympic-marathon-shifting-cities-to-avoid-the-heat-a-sports-physiologist-explains-126189">Why is Japan's Olympic marathon shifting cities to avoid the heat? A sports physiologist explains</a>
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</em>
</p>
<hr>
<p><strong>Stress</strong></p>
<p>Ever notice you become sweaty when you are stressed? A different type of sweat gland, the <a href="https://www.mayoclinic.org/diseases-conditions/hyperhidrosis/multimedia/sweat-glands/img-20007980">apocrine sweat glands</a>, are associated with hair follicles and often respond to <a href="https://www.ncbi.nlm.nih.gov/pubmed/31128655">emotional stress</a>. </p>
<p>This type of sweat combines with bacteria on your skin and causes body odour.</p>
<p><strong>Menopause</strong></p>
<p><a href="https://www.sciencedirect.com/science/article/abs/pii/S0025619611618119?via%3Dihub">Up to 75% of women</a> experience acute bouts of excessive sweating during menopause, called a hot flush.</p>
<p>The <a href="https://physoc.onlinelibrary.wiley.com/doi/epdf/10.1113/JP271456">amount of sweat</a> produced during a two to three minute hot flush can be similar to the amount produced during exercise.</p>
<p>Most people think hot flushes are caused by increases in core body temperature. But <a href="https://journals.lww.com/menopausejournal/fulltext/2019/09000/Is_core_temperature_the_trigger_of_a_menopausal.12.aspx">our research</a> suggests this might not be the case.</p>
<p><strong>Drinking alcohol</strong></p>
<p>Having a couple of drinks with friends may also <a href="https://www.sciencedirect.com/science/article/abs/pii/S0741832905001503?via%3Dihub">increase the sweat response</a>. Alcohol raises your heart rate and causes the blood vessels in your skin to relax and widen. This increases skin redness and your sweat rate, which can actually lead to decreases in body temperature.</p>
<h2>So, what can I do about it?</h2>
<p>Excessive sweating (<a href="https://www1.racgp.org.au/newsgp/clinical/what-is-hyperhidrosis">hyperhidrosis</a>) can happen in unusual situations such as in a cooler climate or with seemingly no cause.</p>
<p>Although it can be embarrassing and uncomfortable, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4012678/">there are ways to treat it</a>, which you can discuss with your doctor. </p>
<p>One option is to use an antiperspirant with aluminium or topical aluminium salts, which blocks the sweat glands from releasing sweat onto the skin.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-do-men-really-sweat-more-than-women-73903">Health Check: do men really sweat more than women?</a>
</strong>
</em>
</p>
<hr>
<p>A longer-term option may be <a href="https://www.ncbi.nlm.nih.gov/pubmed/19222249">injecting Botulinum toxin</a> (commonly known as Botox) into the skin. This paralyses the injected area (such as the armpits, hands and feet) and prevents the activation of sweat glands. </p>
<p>Other options include using low frequency electrical stimulation (<a href="https://dermnetnz.org/topics/iontophoresis/">iontophoresis</a>), prescription drugs and although controversial, surgery.</p>
<p>For menopausal women, <a href="https://www.ncbi.nlm.nih.gov/pubmed/27163520">we have shown</a> closely supervised exercise training can improve temperature regulation, leading to fewer and less severe hot flushes.</p>
<p>This training involved 16 weeks of supervised, progressive moderate-intensity aerobic exercise, such as treadmill and cycling exercise, for up to one hour for three to five days a week.</p>
<h2>In a nutshell</h2>
<p>In the end, sweating is usually our body’s natural way to protect us from overheating. But if excess sweating is a problem, see your doctor who will outline which treatment options are best for you.</p><img src="https://counter.theconversation.com/content/131135/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Sweating is usually our body’s way of stopping us from overheating. But if excess sweating is a problem for you, there’s help.Tom Bailey, Research Fellow, The University of QueenslandFaith Pizzey, PhD Student in Cerebrovascular Physiology, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/710042017-02-13T00:47:11Z2017-02-13T00:47:11ZHealth Check: do cold showers cool you down?<figure><img src="https://images.theconversation.com/files/155089/original/image-20170201-3248-k045o9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">On a hot day, does taking a cold shower make you cooler?</span> <span class="attribution"><span class="source">from www.shutterstock.com.au</span></span></figcaption></figure><p>It’s normal to feel hot, sweaty and uncomfortable in warm weather, but what’s the best way to cool down? To answer this question, we first need to look at how the body maintains stable internal (core) temperature.</p>
<p>We feel uncomfortable at hot environmental (ambient) temperatures because our bodies are striving to maintain a constant core temperature. When the ambient temperature is too high, we engage in reflexive (things our nervous system does without us realising) and behavioural (things we do) adaptations to try to cool ourselves. The discomfort we feel is the motivation for the behavioural adjustments. Many of us just want to jump in a cold shower. So will this help to cool us down? </p>
<p>From the physiological perspective, core temperature is what our body is regulating. Small changes in core temperature can quickly lead to illness (such as heat exhaustion, fever and heat stroke). We are not consciously aware of our core body temperature. Although the body has sensors that monitor core body temperature, our perception of temperature comes exclusively from skin temperature sensors (temperature receptors). These allow us to sense if we are cold, comfortable or hot.</p>
<p>Human biology is remarkable; we maintain a relatively stable core body temperature over a wide range of ambient temperatures. For instance, core body temperature only differs by 0.5⁰C over a wide ambient temperature range (as wide as <a href="http://link.springer.com/article/10.1007%2Fs00484-013-0673-8">12-48⁰C</a>). The body’s ability to restrict core temperature to such a tight range means reflexes to control core temperature need to occur before there is an actual change in core temperature.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/156143/original/image-20170209-28708-1puwk99.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/156143/original/image-20170209-28708-1puwk99.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/156143/original/image-20170209-28708-1puwk99.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=371&fit=crop&dpr=1 600w, https://images.theconversation.com/files/156143/original/image-20170209-28708-1puwk99.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=371&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/156143/original/image-20170209-28708-1puwk99.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=371&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/156143/original/image-20170209-28708-1puwk99.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=466&fit=crop&dpr=1 754w, https://images.theconversation.com/files/156143/original/image-20170209-28708-1puwk99.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=466&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/156143/original/image-20170209-28708-1puwk99.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=466&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Controlling blood flow to the skin, along with sweating, is an important way of controlling internal body temperature.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Controlling blood flow to the skin is an important way of controlling internal body temperature. The circulatory system moves blood around the body; it also transports heat around the body, so changing where the blood flows allows the body to determine where the heat goes. With reduced blood flow to the skin, heat is conserved in the body, and with increased blood flow to skin, heat is lost to the environment.</p>
<p>In cold environments, there is almost no blood flow to the skin to keep all the heat in (which is why we get frostbite). This is why, when we’re very cold, our skin is pallid and pale. At hot ambient temperatures, skin blood flow can increase to as much as seven litres per minute to try to expel all the heat through the skin. This is <a href="http://www.nejm.org/doi/full/10.1056/NEJMra011089">a 23-fold increase</a> to normal, and about 35% of the total volume of blood volume pumped from the heart. This is why, when we’re hot, we can appear flushed.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/156144/original/image-20170209-28712-d3t6zn.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/156144/original/image-20170209-28712-d3t6zn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/156144/original/image-20170209-28712-d3t6zn.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=392&fit=crop&dpr=1 600w, https://images.theconversation.com/files/156144/original/image-20170209-28712-d3t6zn.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=392&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/156144/original/image-20170209-28712-d3t6zn.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=392&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/156144/original/image-20170209-28712-d3t6zn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=493&fit=crop&dpr=1 754w, https://images.theconversation.com/files/156144/original/image-20170209-28712-d3t6zn.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=493&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/156144/original/image-20170209-28712-d3t6zn.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=493&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In cold environments restricting blood flow to the skin is crucial for maintaining core body temperature.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The exquisite control of blood flow to the skin means there is an optimum ambient temperature (known as thermoneutral), where the body does not engage in any regulatory activity to maintain core temperature. This occurs when the skin blood flow is <a href="http://www.sciencedirect.com/science/article/pii/S1566070216300029">about 300mL a minute</a>. </p>
<p>Other mechanisms for temperature control are quite different. In cold environments, the body increases heat generation to <a href="http://www.sciencedirect.com/science/article/pii/S1566070216300157">maintain core temperature</a>. One method is to move the muscles to heat them up (shivering thermogenesis); another is to speed up metabolism to produce more heat (non-shivering thermogenesis).</p>
<p>In hot environments, when air temperature is higher than skin temperature (above roughly 33⁰C), heat loss only takes place with sweating. When sweat evaporates off our skin, it <a href="http://physics.stackexchange.com/questions/255016/evaporation-of-water">has a cooling effect</a>. Sweating, or wet skin, can increase the amount of heat lost from the body by as much as <a href="http://www.sciencedirect.com/science/article/pii/0013935167900023">ten times</a>.</p>
<p>Given free range, animals will spend most of their time in a <a href="http://jap.physiology.org/content/92/6/2667">thermoneutral environment</a>, where they are most comfortable (the comfort zone). Humans are most comfortable (thermoneutral) <a href="http://www.sciencedirect.com/science/article/pii/0013935167900023">at an ambient temperature of about 28⁰C</a> (and a skin temperature of 29-33⁰C). The further we are away from that temperature (either cold or warm), the more uncomfortable we feel.</p>
<h2>The verdict</h2>
<p>Our bodies respond more to changes in skin temperature <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2290547/">than core temperature</a>. So, if we cool part of the body (for instance with a cold sponge, or cold shower), skin blood flow decreases and <a href="https://www.jstage.jst.go.jp/article/physiolsci/57/4/57_4_241/_article">skin temperature falls</a>. </p>
<p>Here we “feel” cooler because cold water causes cold temperature receptor activation in the skin. We may also feel more comfortable, as our skin temperature enters the comfort zone. But because there is less blood flowing to the skin, we’ll actually keep more heat inside, thus leading to an unintended overall increase in core temperature. </p>
<p>A cold shower to “cool off” might seem a good immediate choice. We feel cooler because of the combination of the cold water and the decreased blood flow to the skin, but in fact our core will get warmer because of reduced heat loss from the body without skin blood flow. Some minutes later, we feel hot again. But a warm sensation on the skin will lead to increased blood flow to the skin, increasing heat loss from the body. </p>
<p>So, keeping cool in summer will be more effective with a warm shower (water temperature about 33⁰C) rather than a cold shower (water temperature 20-25⁰C). It will seem warm initially but after a few minutes will provide better comfort in the long term.</p><img src="https://counter.theconversation.com/content/71004/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Some people swear by cold showers to cope with a long, hot summer. Here’s why they’d be better off taking a warm one.Yossi Rathner, Lecturer in Human Physiology, Swinburne University of TechnologyJoshua Luke Ameliorate, Lecturer in Human Anatomy, Swinburne University of TechnologyMark Schier, Senior Lecturer in Physiology, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/684542016-11-13T06:58:17Z2016-11-13T06:58:17ZWhat our ancestors’ third eye reveals about the evolution of mammals to warm blood<figure><img src="https://images.theconversation.com/files/145052/original/image-20161108-16702-ycblag.JPG?ixlib=rb-1.1.0&rect=1060%2C243%2C3951%2C3441&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The fossilised skull of an Odontocyclops displays its pineal foramen.
</span> <span class="attribution"><span class="source">Nkansahrexford (Own work) via Wikimedia Commons</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>French philosopher René Descartes <a href="http://plato.stanford.edu/entries/pineal-gland/">believed</a> that the pineal gland, a tiny button of neurons located in the depth of our brain, was the seat of the soul.</p>
<p>Today, thanks to palaeontology, genetic and developmental studies, we know that it is actually the evolutionary relic of a long-vanished organ, the third eye. This is also known as the pineal eye and is a receptor located on the top of the head. Many existing reptiles such as monitor lizards, some iguanas and the <a href="http://www.doc.govt.nz/nature/native-animals/reptiles-and-frogs/tuatara/">tuatara</a> still have a pineal eye.</p>
<p>All reptiles that still have the pineal eye today are “cold blooded”; they have what’s known as an ectotherm metabolism. Modern mammals – which of course have “warm blood” or an endotherm metabolism – don’t have a pineal eye. </p>
<p>Our group of researchers at the University of the Witwatersrand wondered whether being able to pinpoint when pre-mammalian species lost their pineal eye might unlock the secret of when “warm bloodedness” become a mammalian hallmark. That’s what drove <a href="https://www.app.pan.pl/archive/published/app61/app002192015.pdf">an ambitious study</a> using fossil remains from South Africa’s Karoo region. </p>
<p>We were proved right: our research revealed that mammalian ancestors likely shifted from “cold” to “warm” blood 246 million years ago. This was 10 million years before the first dinosaur even appeared.</p>
<h2>Why have a third eye?</h2>
<p>As with a regular eye, the pineal eye is made up of a cornea, a lens and a retina. Our paired eyes and the reptilian pineal eye are also very similar in terms of embryological development and the genes expressed during this. The pineal eye differs from a regular eye, though, in that it’s usually covered by a thick and large scale and can differentiate between light and dark only.</p>
<p>Our regular eyes can also see variations between light and dark, day and night – so what’s the point of having an organ as redundant as the pineal eye? <a href="https://books.google.co.za/books?id=pkDgJBd4O6oC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false">Research</a> shows that in reptiles the pineal eye acts as a calendar. It can see days getting longer and nights getting shorter, and the reverse, and so tells the brain how seasons are changing. As a consequence, it monitors most life cycles such as sleep and reproduction rhythms. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/145388/original/image-20161110-25090-ovuv8w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/145388/original/image-20161110-25090-ovuv8w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/145388/original/image-20161110-25090-ovuv8w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/145388/original/image-20161110-25090-ovuv8w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/145388/original/image-20161110-25090-ovuv8w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/145388/original/image-20161110-25090-ovuv8w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/145388/original/image-20161110-25090-ovuv8w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/145388/original/image-20161110-25090-ovuv8w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Komodo dragons and some other reptiles still have a pineal eye.</span>
<span class="attribution"><span class="source">Arturo de Frias Marques (Own work) via Wikimedia Commons</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p><a href="https://www.jstor.org/stable/30156149?seq=1#page_scan_tab_contents">Surgical experiments</a> on lizards have also shown that removing the pineal eye affects their capacity to regulate their body temperature, a process called thermoregulation. </p>
<p>This is fascinating since our pre-mammalian ancestors did have a pineal eye and lost it in the course of their evolution toward a more mammalian condition. This suggested that by following the reduction and disappearance of the pineal eye through millions of years, we might be able to point out the time when our ancestors became “warm blooded”.</p>
<h2>A gateway to ancient metabolism</h2>
<p>The pineal eye’s evolution is easy to study. It has an unmistakable bony correlate, the pineal foramen. This is a tube that pierces the skull roof for the pineal eye and nerve. </p>
<p>Most of our ancestors, the pre-mammalian therapsids, had such a foramen on the top of their heads, as can be seen in their fossilised skulls, and thus had a pineal eye. It’s reasonable to assume that this organ fulfilled a similar role in thermoregulation as it does in today’s reptiles.</p>
<p>By checking for the pineal foramen in fossils, we reasoned, it would be possible to trace back the transition from a “reptile-like” to a “mammal-like” metabolism in the lineage that eventually led to mammals.</p>
<p>So our team of palaeontologists and neurologists checked for the pineal foramen in more than 600 skulls. These were all found in the <a href="https://www.wits.ac.za/esi/fossil-collections/">Karoo’s incredibly rich fossil-bearing deposits</a> and dated back to between 300 million and 200 million years ago. </p>
<p>That’s an important time period, since South Africa was situated close to the South Pole at that time thanks to <a href="http://www.varsityfield.com/uploads/1/3/0/5/13050122/theme_11.pdf">continental drift</a>. The climate, then, was much colder and drier, and the contrast between the country’s seasons was greater than today. This implies that species with “cold blood” must have had a pineal eye to help them regulate their body temperature. </p>
<p>To find a species that lived under such harsh conditions without a pineal foramen would strongly suggest that this species was “warm blooded” and that a pineal eye was no longer required to survive. </p>
<h2>An evolutionary step forward</h2>
<p>We found that the pineal foramen was present in most pre-mammalian therapsids before 260 million years ago. After this the feature was increasingly absent. This suggests the pineal eye became dispensable and wasn’t needed for survival any more. </p>
<p>The increasing loss of the pineal foramen occurred in two lineages. One of these, the <a href="https://global.britannica.com/animal/cynodont">cynodonts</a>, led to mammals. In their case, the pineal foramen disappeared entirely 246 million years ago. It’s then, we believe, that the transition from “cold blood” to “warm blood” was achieved.</p>
<p>More work needs to be done to test this evolutionary scenario, but if it proves true it would mean that mammals had likely already evolved one of the key adaptations that enabled them to survive for more than 200 million years through the reign and extinction of dinosaurs and two mass extinctions to the present day.</p><img src="https://counter.theconversation.com/content/68454/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Julien Benoit receives funding from PAST and its Scatterlings projects; the National Research Foundation of South Africa; and the DST-NRF Centre of Excellence in Palaeosciences (CoE in Palaeosciences). </span></em></p>Mammals’ ancestors had a third eye and the fossil record of its disappearance tells us the story of the evolution of one of our most important features: warm blood.Julien Benoit, Postdoc in Vertebrate Palaeontology, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/647672016-09-08T09:59:54Z2016-09-08T09:59:54ZRio Paralympics: athletes with spinal-cord injuries tend to overheat<p>The body is able to maintain a stable core body temperature in a range of environments. This process – called thermoregulation – balances heat production and heat loss to the environment. Two important mechanisms involved in heat loss are the evaporation of sweat and the control of blood flow to the skin. But what happens if your whole body can’t do this? This is the situation people with spinal-cord injuries face.</p>
<p>People with a spinal-cord injury are not able to produce sweat or control blood flow below the level of their spinal injury. The extent of the thermoregulatory impairment depends on the level of the injury. For instance, the higher the spinal injury, the smaller the body surface that is able to sweat and so the greater the thermoregulatory impairment. </p>
<p>When able-bodied people exercise, a large amount of energy is released as heat (about 80% depending on the activity) causing a disturbance of heat balance. To stabilise core body temperature, skin blood flow and sweating are raised. But what happens when athletes with a spinal-cord injury exercise?</p>
<p>Previously, researchers have only investigated the thermoregulatory responses of people with a spinal-cord injury during continuous, steady-state exercise in <a href="http://bit.ly/2crghKY">warm environments</a>. This doesn’t represent the nature or the environmental conditions of the sports many people with a spinal-cord injury play. For example, both <a href="http://iwbf.org/the-game/#rules">wheelchair basketball</a> and <a href="http://www.iwrf.com/?page=about_our_sport">wheelchair rugby</a> are played indoors in air-conditioned sport halls. Also, the exercise isn’t steady state, it involves intermittent, short bursts of activity. </p>
<p><a href="http://www.ncbi.nlm.nih.gov/pubmed/25365654">A recent study from our lab</a> has revealed that even at 20°C (typical ambient temperature of a sports hall) during intermittent sprint wheelchair exercise, athletes with tetraplegia – injury to the cervical (upper) region of the spine – experience a continual increase in core body temperature. Despite similar external workloads, core body temperature plateaued in people with paraplegia – injury to the thoracic or lumbar (lower) portions of the spinal cord. Even though both groups had a spinal-cord injury, large differences in their thermal response were apparent due to differences in their heat-loss capacity.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/136871/original/image-20160907-25266-c9h3in.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/136871/original/image-20160907-25266-c9h3in.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/136871/original/image-20160907-25266-c9h3in.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/136871/original/image-20160907-25266-c9h3in.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/136871/original/image-20160907-25266-c9h3in.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/136871/original/image-20160907-25266-c9h3in.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/136871/original/image-20160907-25266-c9h3in.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Parts of the spine.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-155445686/stock-photo-spine-anatomy-labeled.html?src=TNxEKauQE3VlYVLMHBvezw-1-45">Alila Medical Media/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>In wheelchair rugby, any person with an impairment to all four limbs can participate, including players with tetraplegia. Unpublished results from our lab have shown that, during a match, despite players with tetraplegia covering about 17% less distance and pushing on average about 10% slower than players with other physical impairments, their core body temperature increased by a much larger amount. </p>
<h2>Cooling but no performance boost</h2>
<p>In the able-bodied, cooling strategies have been <a href="http://bit.ly/2c0lcTY">heavily researched</a>, but the same can’t be said for athletes with a spinal-cord injury, despite their thermoregulatory impairment. <a href="http://www.ncbi.nlm.nih.gov/pubmed/?term=griggs+cooling+spinal">Previous studies</a> on cooling methods for athletes with spinal injuries hasn’t considered whether or not they are practical. For instance, applying hand cooling during breaks in play is not practical for wheelchair athletes as their hand dexterity would be severely affected. </p>
<p>Two methods that are commonly used by athletes with a spinal-cord injury are the use of water sprays between breaks in play and the application of ice vests before exercise (pre-cooling). We recently investigated how effective these methods are at reducing the rise in core body temperature and the effect on wheelchair rugby performance. </p>
<p>We found that water spraying between breaks in play combined with pre-cooling with an ice vest lowered core body temperature to a greater degree than pre-cooling only or no cooling at all. Surprisingly, even pre-cooling only led to a lower increase in core body temperature throughout the 60 minutes of exercise compared with no-cooling. Despite this, neither cooling condition had a positive effect on wheelchair rugby performance. We currently don’t know how effective just water spraying is or whether other cooling methods used by able-bodied athletes could be more beneficial. </p>
<p>The specific sporting regulations and logistics of administering a cooling method need to be carefully considered. In the absence of evidence and large physiological differences between individuals, sport scientists and coaches should take an individualised approach when refining a cooling strategy for athletes with a spinal-cord injury and conduct their own tests prior to use in competition.</p>
<p>So look out for these athletes at Rio trying their best to keep cool.</p><img src="https://counter.theconversation.com/content/64767/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Katy Griggs does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Researchers are finding new ways to keep them cool.Katy Griggs, Research Assistant and PhD student, Loughborough UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/648342016-09-07T11:10:47Z2016-09-07T11:10:47ZElectric fans may not help the elderly in a heatwave<figure><img src="https://images.theconversation.com/files/136714/original/image-20160906-6096-yft4sl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-400947790/stock-photo-old-metal-fan-on-white-wall-background-vintage-color.html?src=wixUXJlaNfL3AmydWh7xng-1-41">imnoom/Shutterstock.com</a></span></figcaption></figure><p>Researchers <a href="http://jama.jamanetwork.com/article.aspx?articleid=2547743">have found</a> that when elderly people use an electric fan in extreme heat, instead of cooling them down, it actually raises their core body temperature and increases their heart rate.</p>
<p>Our bodies produce heat all the time. We need to lose this heat or we would overheat very quickly. Normally this happens in a number of ways: by heat radiation, by contact warming of the air that is around our body, by warming the air that we breath in, and by evaporating sweat from our skin. </p>
<p>A fan normally increases the heat loss from our skin to the air around us and stimulates the evaporation of our sweat, too. But when the air gets hotter, and it becomes warmer than our skin, the body will absorb heat from the air instead of losing to it. A fan in that case will increase the amount of heat absorbed, just as a fan-assisted oven heats food faster than a conventional one. </p>
<p>Despite this, the fan will still help evaporate our sweat. So whether a fan is good or bad in the heat depends on the balance between increased body heating and the extra cooling from sweat evaporation. The question is: up to what temperature is a fan helpful in cooling you down?</p>
<p>In 2015, <a href="http://jama.jamanetwork.com/article.aspx?articleid=2110959">Ravanelli and colleagues</a> showed that even at 42ºC, young people benefit from an electric fan, up to 50% humidity, which means it would be effective in most heatwaves. But in this week’s paper, <a href="http://jama.jamanetwork.com/article.aspx?articleid=2547743">Gagnon and colleagues</a> repeated the experiment with people between the ages of 60 and 80 and found no benefit of the fan to the experienced heat stress. In fact, there were negative effects for some of the participants. </p>
<h2>Different physiology</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/136866/original/image-20160907-25257-sbpi9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/136866/original/image-20160907-25257-sbpi9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/136866/original/image-20160907-25257-sbpi9n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/136866/original/image-20160907-25257-sbpi9n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/136866/original/image-20160907-25257-sbpi9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/136866/original/image-20160907-25257-sbpi9n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/136866/original/image-20160907-25257-sbpi9n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">We sweat less as we age.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/downloading_tips.mhtml?code=&id=79797508&size=medium&image_format=jpg&method=download&super_url=http%3A%2F%2Fdownload.shutterstock.com%2Fgatekeeper%2FW3siZSI6MTQ3MzI2ODgwOSwiYyI6Il9waG90b19zZXNzaW9uX2lkIiwiZGMiOiJpZGxfNzk3OTc1MDgiLCJrIjoicGhvdG8vNzk3OTc1MDgvbWVkaXVtLmpwZyIsIm0iOiIxIiwiZCI6InNodXR0ZXJzdG9jay1tZWRpYSJ9LCJrQWlnWkNQVTlCb3RwelBvd21YYVllSG1jWm8iXQ%2Fshutterstock_79797508.jpg&racksite_id=ny&chosen_subscription=1&license=standard&src=DjSyFpk7dtEcnEnRZpLykA-1-14">Lisa F. Young/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>The body’s ability to keep its temperature in a safe range (thermoregulation) becomes less effective as we age. Blood vessels in the skin that open up to allow heat – transported from the body’s core – to dissipate are less responsive in the elderly. People also tend to sweat less as they get older, so the cooling that’s achieved when their sweat evaporates is reduced, too. </p>
<p>In Gagnon’s study, the researchers put the elderly participants in a room of 42ºC, once with and once without the fan on, just as Ravanelli did with the young people. They started with quite dry air (30% humidity) and then incrementally raised the humidity in the room every five minutes up to 70% humidity. The point at which a participant’s body temperature and heart rate started to increase, they called critical humidity. </p>
<p>If a fan causes a higher critical humidity, it would imply that it helps to reduce the heat load. But while Ravanelli found that this was the case in young people, in the present study with the older group the responses were mixed. For the older group (looking at the average values for the group), the critical humidity stayed the same, so no benefit or worsening was observed. But, worryingly, in at least two people a substantially worse outcome was observed with the fan on. When looking at the heart rates and body temperatures across the experiment, the researchers found that with the fan on, these indicators of the body’s strain were significantly higher. In other words, things got worse with the fan.</p>
<p>Why this difference between old and young? In order to get the benefit of the fan at these high temperatures, the fan has to cause a substantial increase in the evaporation of sweat. This increase was seen in young people, but not in the study of older people. Their sweat rate didn’t increase, which is probably part of the reason why electric fans failed to cool the elderly.</p>
<p>But this is probably not the final word on the topic. The temperature chosen for this paper (42ºC) and the fan speed was quite extreme, so there may be benefits at lower temperatures and different fan speeds. Also, other solutions – such as spritzing the skin with a water atomiser to increase evaporation – haven’t yet been explored. Given the impact expected from climate change, and the need to reduce the energy cost of cooling solutions, this topic will undoubtedly get more attention in the future.</p><img src="https://counter.theconversation.com/content/64834/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>George Havenith does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>An electric fan cools you down in extreme heat, but not if you’re old.George Havenith, Professor of Environmental Physiology and Ergonomics, Dean of Loughborough Design School, Loughborough UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/627532016-07-19T17:48:35Z2016-07-19T17:48:35ZFrom perspiration to world domination – the extraordinary science of sweat<figure><img src="https://images.theconversation.com/files/131129/original/image-20160719-7903-1ozfw05.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Per litre of sweat produced, we can dump around half a million calories of heat from our bodies.
</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/cat.mhtml?lang=en&language=en&ref_site=photo&search_source=search_form&version=llv1&anyorall=all&safesearch=1&use_local_boost=1&autocomplete_id=&search_tracking_id=g9Sz3_xPH9hMxsIgn6_t8g&searchterm=sweating%20in%20the%20gym&show_color_wheel=1&orient=&commercial_ok=&media_type=images&search_cat=&searchtermx=&photographer_name=&people_gender=&people_age=&people_ethnicity=&people_number=&color=&page=1&inline=428924680">Maridav/Shutterstock</a></span></figcaption></figure><p>I’m writing this on the UK’s hottest day of the year. There is a light breeze, but everyone I have seen today has beads of sweat on their forehead. Seeing someone wiping their brow is a fairly common sight in midsummer, but it reveals a simple and fascinating truth about our species: without sweat, we would not still be here. Without this absolutely amazing technology we would not have climbed our way to the top of the evolutionary pile. Many animals perspire, but no others use it as such an efficient and refined cooling technology. So how does it work and why do we owe it so much?</p>
<p>We often assume that it is our brain power that differentiates us from other animals. It is obvious that we are able to process more intellectual stimuli than other mammals, but any PC owner knows that computational power is completely useless if the cooling system fails. And this is what really sets us apart. It is our ability to maintain an effective working temperature, not just so that we can keep moving, but so that we can keep thinking while in motion, efficiently chasing down the quarry.</p>
<p>As a species, over short distances, we are hopeless runners. We might be able to go a long way but what use is that if we can’t catch anything? The truth is that we never could if it weren’t for several factors that make us identifiably human. And it is our ability to perspire which renders them all effective. So we may have perfect bodies for distance running, but those features that enable us to move so effectively are useless without correct temperature control.</p>
<h2>Two legs are better than four</h2>
<p>There are distinct thermoregulatory advantages to being a two-legged human. Being merely upright, for example, means that less of the sun hits you when it’s at its hottest. The bipedal human exposes only about <a href="http://www.sciencedirect.com/science/article/pii/004724849190002D">7% of their surface area to sunlight; it is triple this for a quadruped</a>. This fact alone means that being on two legs enables you to move with greater heat efficiency. </p>
<p>Also, by being upright, we can take advantage of the fact that our brains are further away from the harsher micro-climate at ground level. It is hotter there because it is heated by the sun and because there is less air movement. And with air movement comes evaporation, which is the real miracle technology. Evaporation is such an effective way to lose heat that if a litre of sweat is able to evaporate on the surface of your skin, you can lose about half a million calories of heat in the process.</p>
<p>While most quadrupeds sweat, they do so to maintain skin health and create scent (we do this, too), and even to create ear wax (<a href="https://www.ncbi.nlm.nih.gov/pubmed/9433684">which, amazingly, is a sort of sweat</a>). But for thermoregulation, most animals use interior air movement (panting) to cool down – where their bodies have to <a href="http://wiki.ggc.usg.edu/wiki/Panting_as_a_thermoregulation_strategy">actively work to lose heat</a>. So that means, on a hot day, we could chase down a quadruped, and when it stopped to shed some heat, we humans could keep going and close the gap a little. Eventually, the distance between predator and prey would close as their technology failed, and ours kept functioning. Sweat meant that <a href="http://www.sciencedirect.com/science/article/pii/004724849190002D">we were much better hunters than we appeared</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/131124/original/image-20160719-8062-yubw4r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/131124/original/image-20160719-8062-yubw4r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/131124/original/image-20160719-8062-yubw4r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/131124/original/image-20160719-8062-yubw4r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/131124/original/image-20160719-8062-yubw4r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/131124/original/image-20160719-8062-yubw4r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/131124/original/image-20160719-8062-yubw4r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In every bead of sweat there is sodium, potassium, calcium, magnesium, zinc, copper, iron, chromium, nickel and lead.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-359436725/stock-photo-forehead-sweat.html?src=FT9LP0i-3_3aACtxOhE7dA-1-0">Chaikom/Shutterstock</a></span>
</figcaption>
</figure>
<h2>Conflicting sweat signals</h2>
<p>It is decidedly odd that sweat is taboo in our society. Do it in the wrong place or from the wrong part of your body and the people around you will become uncomfortable, or at the very least make you feel so … and that will probably make you sweat.</p>
<p>Sweat in a gym and it’s aesthetic: it’s a badge of honour. It’s part of the training montage of any sports movie you might think of. But get it wrong – sweat in a job interview, a presentation, or in a social situation – and people will think you’ve lost control, or that it’s a stress response because you are deceiving them. But without it we would never have become who we are, have survived to the point when we could invent things, create art, make music, or surf the net.</p>
<p>So as you struggle through the next few days of hot weather, think of those beads of sweat on your forehead, and the fact that the exposed skin there, and its ability to perspire, is what keeps your brain functioning in the heat. In the past, it made you a lethal weapon out on the savanna, now it might allow you to reflect on what it has allowed you to achieve in the past, and that without those <a href="http://www.sweathelp.org/home/understanding-hyperhidrosis.html">2.5m sweat glands</a> on your skin working to maintain the correct temperature for thought, you would not be here, reading this.</p><img src="https://counter.theconversation.com/content/62753/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Vybarr Cregan-Reid receives funding from Arts Council England. He is the author of 'Footnotes: how running makes us human' published by Ebury.</span></em></p>Our success as a species is 5% inspiration and 95% perspiration.Vybarr Cregan-Reid, Reader in English and Environmental Humanities and Author of Footnotes: How Running Makes us Human (Ebury, 2016), University of KentLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/455852015-08-03T20:07:42Z2015-08-03T20:07:42ZWhy is it so cold in here? Setting the office thermostat right – for both sexes<figure><img src="https://images.theconversation.com/files/90568/original/image-20150803-6008-xv4jmh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Keeping office workers from feeling too hot or too cold is no simple task.</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-136658537/stock-photo-office-worker-with-mustache-in-cold-snow-frosty.html?src=MuzBBMwyBIp7ESaKeSjMaw-1-0">Kjetil Kolbjornsrud/Shutterstock</a></span></figcaption></figure><p>If you work in an office, chances are you or the person sitting next to you has grumbled about it being too hot or cold. No one likes rugging up on a summer’s day to contend with the air-conditioning. Or having to shed one too many layers in winter to compensate for stifling heat indoors.</p>
<p>According to a <a href="http://nature.com/articles/doi:10.1038/nclimate2741">paper published today</a> in the journal Nature Climate Change, this scenario is more likely if you’re a woman. Climate control systems in office buildings are often set according to an old formula based on men’s thermal comfort. This gender bias, the authors argue, is wasting energy. </p>
<h2>What is thermal comfort?</h2>
<p>Keeping office workers from feeling too hot or too cold is no simple task. While most office air conditioners control only air temperature, the way we exchange heat with the environment depends on a suite of environmental factors. And so does our thermal comfort. </p>
<p>Engineers need to consider:</p>
<ul>
<li>the humidity</li>
<li>the movement of air (wind speed)</li>
<li>the radiation temperature (the temperature of everything the body can “see”)</li>
<li>the temperature of everything we touch. </li>
</ul>
<p>In the 1970s, Danish engineer Ole Fanger <a href="http://trove.nla.gov.au/work/19332073?selectedversion=NBD3968716">developed a model</a> to determine the combination of environmental variables that we find comfortable. </p>
<p>Because heat exchange also depends on individual factors such as body size (and therefore body surface area), metabolic rate (that determines metabolic heat production), tissue insulation (related to the amount of body fat), and clothing, Fanger’s own experiments showed that no office thermal environment ever would satisfy everyone. </p>
<p>Even before Fanger, we knew that, at the low wind speeds typical of offices, radiant heat exchange mattered more than convective heat exchange. In other words, radiation temperature is <a href="http://link.springer.com/article/10.1007%2FBF00596389#page-1">more important</a> for thermal comfort than air temperature. You could argue that offices should have wall conditioners, rather than air conditioners.</p>
<p>In today’s <a href="http://nature.com/articles/doi:10.1038/nclimate2741">Nature Climate Change paper</a>, Dutch researchers Boris Kingma and Wouter van Marken Lichtenbelt show that if the thermostat is set for men, as it usually is, the air temperature will be too low for women. </p>
<p>Because women are smaller, the authors explain, they generate less metabolic heat than men, and so will not feel comfortable in winter at office temperatures set for men. </p>
<p>By the same logic, if the thermostat is set for Europeans, it will be too low for Asians, who weigh, on average, <a href="http://www.biomedcentral.com/1471-2458/12/439">30% less</a> than Europeans. </p>
<p>In countries such as Australia and South Africa, where air conditioning generally is used for cooling, setting the thermostat to satisfy large people in summer will leave smaller people feeling too cold. </p>
<p>But while Fanger’s equations predict thermal comfort – how satisfied we are with the thermal environment – that is only one of the body functions relevant to the question of where we set the thermostat. </p>
<h2>More than just comfort</h2>
<p>Heat exchange also affects our body temperature control (how hot our bodies are), thermal sensation (how hot or cold we feel the environment to be), and our performance (how well we do on a particular task). </p>
<p>Those body functions are not necessarily correlated. In a hot bath, for instance, body temperature rises and we feel hot, but we meet Fanger’s criterion for thermal comfort: we wouldn’t want the temperature to be any different. </p>
<p>We perform some cognitive and physical tasks <a href="https://www.crcpress.com/Human-Thermal-Environments-The-Effects-of-Hot-Moderate-and-Cold-Environments/Parsons/9781466595996">best</a> when we’re slightly-uncomfortably cold. But manual dexterity <a href="http://www.researchgate.net/publication/16490092_A_laboratory_study_of_the_effects_of_moderate_thermal_stress_on_the_performance_of_factory_workers">is better</a> at a warm 32°C than at 20°C in simulated factory work. </p>
<p>Performance at some tasks drops off when body temperature rises, even if we do not feel the environment as warm. For that reason, and those outlined in the Nature Climate Change paper, children <a href="http://reference.sabinet.co.za/webx/access/journal_archive/00382353/8184.pdf">probably underperform</a> on learning tasks in classrooms that teachers assess as feeling just right. Perhaps the smaller children should set the thermostat.</p>
<p>As if all that complexity weren’t enough, Australian researchers have <a href="http://www.sciencedirect.com/science/article/pii/S0378778897000534">challenged</a> Fanger’s 1970s thermal comfort model on the basis of the concept of adaptive thermal comfort. Should we set the thermostat at the same level in winter, they asked, when we are acclimated to colder outdoor environments, as in summer? </p>
<p>Some occupants of offices in the tropics <a href="https://escholarship.org/uc/item/9c40787v">want the thermostat</a> set higher than Fanger predicts. Thirty years ago, people of European ancestry living in Darwin <a href="http://link.springer.com/article/10.1007%2FBF02189471#page-1">rejected</a> air conditioning in the “the Dry” (July and August) because they felt overcooled. Though it’s unclear whether modern Darwinians, many of whom use air-conditioning at home, would say the same. </p>
<h2>So, what can we do?</h2>
<p>We certainly could maintain thermal comfort and simultaneously relax the demands on the thermostat if we were prepared to wear warmer clothes in our offices in winter and cooler clothes in summer. Selecting clothing also would solve the dilemma of providing thermal comfort to both men and women in the same office. </p>
<p>In the new Nature Climate Change paper, the authors estimate that energy consumption of residences and offices “adds up to about 30% of total carbon dioxide emissions”. </p>
<p>It’s true, we could <a href="http://au.wiley.com/WileyCDA/WileyTitle/productCd-0470453613.html">substantially reduce</a> the energy required for acceptable thermal environments in offices and consequently reduce greenhouse gases. But that approach would require us to abandon the compulsion to create a shirt-sleeve thermal environment in offices, and to vary the thermostat between summer and winter. </p>
<p>We would also need to switch to wall-conditioning rather than air-conditioning and use green engineering to get the thermal design of the office building right. We can be comfortable without it costing the earth.</p><img src="https://counter.theconversation.com/content/45585/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shane Maloney receives funding from The Australian Research Council and Meat and Livestock Australia. He is affiliated with The National Tertiary Education Union as a member of the UWA branch committee.</span></em></p><p class="fine-print"><em><span>Andrea Fuller receives funding from grants from the National Research Foundation, South Africa.</span></em></p><p class="fine-print"><em><span>Duncan Mitchell receives funding from the South African Medical Research Council, the South African National Research Foundation, the Australian Research Council and Oppenheimer Memorial Trust, for research related to thermal physiology in non-human mammals and to pain pathophysiology. The South African Medical Research Council funded some research in pain pathophysiology (another research interest of his) as well as research related to thermal physiology in non-human animals. He is Director of Partners in Research (a South African independent pharmaceutical market research company).</span></em></p>If you work in an office, chances are you or the person sitting next to you has grumbled about it being too hot or cold.Shane Maloney, Professor and Head of School, Anatomy Physiology and Human Biology, The University of Western AustraliaAndrea Fuller, Professor, School of Physiology; Director, Brain Function Research Group , University of the WitwatersrandDuncan Mitchell, Honorary Professorial Research Fellow at the University of the Witwatersrand, Johannesburg; Adjunct Professor in the School of Anatomy, Physiology and Human Biology, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/378052015-03-08T19:01:45Z2015-03-08T19:01:45ZHealth Check: why do some people feel the cold more than others?<figure><img src="https://images.theconversation.com/files/74039/original/image-20150306-3321-skvfad.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Women often report that they feel colder than men in the same environment.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/garryknight/6436100219">Garry Knight/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>When HMS Beagle docked at the southern tip of Tierra del Fuego, <a href="http://darwin-online.org.uk/content/frameset?pageseq=1&itemID=F14&viewtype=text">Charles Darwin remarked</a> on the capacity of the locals to deal with cold:</p>
<blockquote>
<p>A woman, who was suckling a recently born child, came one day alongside the vessel and remained there out of mere curiosity, whilst the sleet fell and thawed on her naked bosom, and on the skin of her naked baby.</p>
</blockquote>
<p>Japanese pearl divers dive for long periods in cold water without the comfort of wetsuits, whereas many of us whimper as the waters of the relatively warm Pacific or Indian Oceans reach our midriff. </p>
<p>Why is there such variation in our reaction to cold?</p>
<p>The perception of cold begins when nerves in the skin send impulses to the brain about skin temperature. These impulses respond not only to the temperature of the skin, but also to the rate of change in skin temperature. </p>
<p>So we feel much colder jumping into cold water, when skin temperature drops rapidly, than after we have stayed there for a while, when our skin temperature is low but constant. </p>
<p>The burst of nerve impulses generated by falling skin temperature provides early warning of an event likely to cause body core temperature (the temperature of the internal organs) to fall. If unchecked, a fall in body core temperature can result in lethal hypothermia. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/74040/original/image-20150306-3321-1vooft9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/74040/original/image-20150306-3321-1vooft9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/74040/original/image-20150306-3321-1vooft9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/74040/original/image-20150306-3321-1vooft9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/74040/original/image-20150306-3321-1vooft9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/74040/original/image-20150306-3321-1vooft9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/74040/original/image-20150306-3321-1vooft9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The perception of cold begins when nerves in the skin send impulses to the brain about skin temperature.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/light_seeker/6487856995">Viewminder/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>In healthy people, physiological systems prevent hypothermia from occurring. Impulses from the skin arrive at the hypothalamus, a brain area responsible for controlling the internal environment of the body, which generates instructions in the nervous system that prevent a drop in body core temperature. </p>
<p>Nervous impulses sent to muscles generate extra metabolic heat through shivering. Blood vessels that would otherwise transport warm blood from the internal organs to the cold skin, where the blood would lose heat, constrict, constraining most blood, and its heat, to the internal organs.</p>
<p>Impulses arriving at the cerebral cortex, the part of the brain where reasoning occurs, generate information about how cold we feel. These combine with impulses arriving from the limbic system, responsible for our emotional state, to determine how miserably cold we feel. These feelings motivate us to perform certain behaviours, such as curling up or putting on more clothes, and to complain.</p>
<p>Feeling cold is not the same as being cold. Jumping into a cool swimming pool feels cold, but it can cause body core temperature to rise because of the warm blood retained in the core. Body temperature can stay elevated for up to an hour. </p>
<p>Many of us also have felt cold at the beginning of a fever, when the body core temperature starts to rise. During a fever, the nerve circuits that control body temperature are reset to a higher level, so the body responds as if it is cold until its temperature stabilises around that higher level. </p>
<p>While fever indicates a problem, is there anything wrong with feeling excessively cold rather than actually being cold? </p>
<p>Some of us have the misfortune to suffer from <a href="http://www.ncbi.nlm.nih.gov/pubmed/24418302">Raynaud’s phenomenon</a>, a condition in which the blood flow is too low to keep the fingers and toes warm. </p>
<p>Feeling excessively cold during pregnancy, when the foetus acts as a small furnace, may be a symptom of low thyroid hormone activity, needing hormone supplementation. </p>
<p>But some healthy people can feel colder than do others in the same environment. Women often report that they feel colder than men in the same environment. This is probably because they have a lower skin temperature, a consequence of more subcutaneous fat and the hormone oestrogen. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/74041/original/image-20150306-3324-mnys31.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/74041/original/image-20150306-3324-mnys31.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/74041/original/image-20150306-3324-mnys31.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/74041/original/image-20150306-3324-mnys31.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/74041/original/image-20150306-3324-mnys31.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/74041/original/image-20150306-3324-mnys31.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/74041/original/image-20150306-3324-mnys31.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Feeling cold is not the same as being cold.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/photosam1000/3179758165">Sam Einhorn/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<p>Some of us may inherit feeling excessively cold. A <a href="http://journals.cambridge.org/download.php?file=%2FTHG%2FTHG15_02%2FS1832427400012007a.pdf&code=c2dd4cd6fa6a89bd5e74d9e8bd98cb77">study of twins</a> found that the prevalence of the feeling of cold hands and feet is highly heritable, implying a genetic basis for exaggerated temperature perception. </p>
<p>Some of us also may feel cold simply because of how others close to us look, a phenomenon called “cold contagion”. In one study, healthy volunteers <a>felt colder</a> if they were shown videos of actors pretending to be cold than if the actors pretended to be warm. The temperature of the volunteers’ hands dropped as the blood vessels to their hands constricted, even though they were not in a cold environment. </p>
<p>Most of us who are healthy but claim to feel excessively cold, however, have only ourselves to blame. Unlike Darwin’s Fuegians, we have habituated ourselves to feeling comfortably warm. In the developed world we rarely expose ourselves to cold, letting expensive clothing protect us from outdoor cold and letting power companies warm our living and working spaces. </p>
<p>Allowing power companies to do the work that our metabolism used to do when we experienced cold may actually <a href="http://www.ncbi.nlm.nih.gov/pubmed/22202013">contribute to obesity</a>. We’d probably all be much better off if we spent more time being cold.</p><img src="https://counter.theconversation.com/content/37805/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Duncan Mitchell receives funding from South African Medical Research Council, South African National Research Foundation, Australian Research Council and Oppenheimer Memorial Trust, for research related to thermal physiology in non-human mammals. He is Director of Partners in Research (a South African independent pharmaceutical market research company).</span></em></p><p class="fine-print"><em><span>Andrea Fuller receives funding from grants from the National Research Foundation, South Africa. </span></em></p><p class="fine-print"><em><span>Shane Maloney receives funding from The Australian Research Council and Meat and Livestock Australia. He is affiliated with The National Tertiary Education Union as a member of the UWA branch committee.</span></em></p>Fever indicates a problem, but is there anything wrong with feeling excessively cold rather than actually being cold?Duncan Mitchell, Honorary Professorial Research Fellow at the University of the Witwatersrand, Johannesburg; Adjunct Professor in the School of Anatomy, Physiology and Human Biology, The University of Western AustraliaAndrea Fuller, Professor, School of Physiology; Director, Brain Function Research Group , University of the WitwatersrandShane Maloney, Professor and Head of School, Anatomy Physiology and Human Biology, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/344892015-01-23T03:37:59Z2015-01-23T03:37:59ZWant to keep cool on hot summer days? Here’s how<figure><img src="https://images.theconversation.com/files/69840/original/image-20150123-12085-1f1itgd.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Water can remove four times as much heat as the equivalent mass of air.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/gabrielap93/5840840759">Gabriela Pinto/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Are neck, hand or forearm cooling, ice-cube sucking or cold showers effective ways to lose heat on those dog days of summer? Can sports clothing keep you cool by wicking away sweat? When the heat is on, some of us are prepared to entertain even snake-oil solutions for the sake of personal comfort, but do such cooling strategies really work?</p>
<p>Let’s first consider heat loss from a physical perspective, putting aside physiological heat-loss mechanisms, such as sweating and skin blood flow. Cooling down is more easily understood when reduced to this level because the physical properties of heat exchange are well known. </p>
<h2>Understanding heat loss</h2>
<p>The first of these properties is the temperature gradient; the bigger the temperature difference between two things, the more rapidly heat (thermal energy) flows towards the cooler one. </p>
<p>Substances conduct heat at different rates (thermal conductivity). Water, for instance, is 24 times more conductive than air at the same temperature. Consider walking into the cold room of a bottle shop, which is usually a cool five degrees Celsius, versus swimming in water of the same temperature. The latter is excruciating, with death from hypothermia just around the corner.</p>
<p>We also need to keep in mind the heat retained within various substances, which is known as mass-specific heat. This tells us how heat is required to increase the heat of two objects that weigh the same by one degree Celsius. Water has a specific heat four times that of air, for instance, so a kilogram of water can remove four times as much heat as the equivalent mass of air.</p>
<p>Density is important too, because it determines the mass of a substance that can be contained within a fixed space. Since water is 800 times denser than air, a bath filled with water is many times heavier than one that contains air.</p>
<p>Together, specific heat and mass define the volume-specific capacity of substances to store heat. Going back to our example with water: it has a heat capacity more than 3,000 times that of air because of the combined effects of its mass-specific heat and density. </p>
<p>An object’s mass and surface area are important as well, because heat is stored in its mass and lost through its surface. Spheres have the largest mass for a given surface area, while wafers have the opposite characteristic. In other words, an object’s surface-area-to-mass ratio dictates its heat-exchange potential, with flatter and thinner surfaces (such as hands and feet) losing heat more rapidly.</p>
<h2>Cooling solutions</h2>
<p>So, to cool an object, maximise the temperature gradient, choose a coolant with a high thermal conductivity and heat capacity (liquids), and modify the shape of your object to resemble a wafer. Without question, water is ideal for cooling non-living objects. </p>
<p>But does it work as well for living bodies? And how is it influenced by the physiological responses that we all experience when exposed to heat? </p>
<p>So far, we have only considered heat conduction, or heat exchanged between objects in direct contact – touching a hot stove for example. But conduction speed is influenced by the distance heat must travel. </p>
<p>Animals enhance cooling by delivering heat closer to the skin surface. This convective mechanism, which involves delivering hotter central-body blood to the cooler skin, shortens the conductive pathway and promotes heat loss. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/69841/original/image-20150123-12120-1s1773s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/69841/original/image-20150123-12120-1s1773s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/69841/original/image-20150123-12120-1s1773s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/69841/original/image-20150123-12120-1s1773s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/69841/original/image-20150123-12120-1s1773s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/69841/original/image-20150123-12120-1s1773s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/69841/original/image-20150123-12120-1s1773s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Natural selection has ensured that naked human skin is ideally suited for evaporative cooling.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/therebel68/198668731">Obi/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>But this mechanism relies on increasing and sustaining skin blood flow, which is dictated by the separate and combined effects of deep-body and local skin temperatures. Maximal skin blood flow occurs only when both the deep-body and local skin tissues are heated, but not if only one region is hot. </p>
<p>When a hot person is placed in very cold water (say of about five degrees Celsius), skin blood flow is dramatically reduced, so heat loss is compromised. Paradoxically, submerging that same person in temperate water (25 degrees Celsius) increases heat dissipation by preventing this blood-flow suppression. </p>
<h2>Clothing and comfort</h2>
<p>Natural selection has ensured that naked human skin is ideally suited for evaporative cooling, and anything placed on the skin interferes with that process. </p>
<p>The average person has some 110 sweat glands per square centimetre of skin (although this varies with location). When heated, these glands secrete sweat that wets the skin. The ensuing evaporation transfers heat to water molecules, which change from a liquid to a gas, leaving the sweating person cooler.</p>
<p>But, in still conditions, the characteristics of the air in direct contact with the skin change; it rapidly becomes warmer and more humid. This warmer air is less dense and spontaneously rises, taking with it heat (natural convection) and water vapour, and permitting the incoming air to be warmed and humidified. </p>
<p>When we move, or when air moves across the skin (forced convection), convective and evaporative cooling are magnified. Clothing reduces these benefits. </p>
<p>So these are the principles that dictate human heat loss. But we must now distinguish between thermal strain and comfort. </p>
<p>Strain is the physiological impact of heating the body, as quantified through deep-body and skin temperatures; comfort relates to the pleasure derived from different thermal states. We now need to consider whether we wish to feel more comfortable or to reduce thermal strain. </p>
<p>Since comfort follows reduced thermal strain, our energies should be directed accordingly. The first strategy should be to resist counter-evolutionary practices designed to minimise strain (heat avoidance, for instance, and air conditioning), and allow our bodies to adapt to seasonal variations.</p>
<p>So, use natural ventilation whenever possible, dress appropriately and experience the climate. With adaptation, you can improve both physiological heat loss and thermal comfort.</p>
<p>The second strategy is for desperate times, like those dog days of summer: water immersion. Showers help, but are very wasteful. Hand and forearm immersion are good, but time consuming. Neck cooling and ice-cube sucking suck! </p>
<p>Instead, bathe in enough temperate water to just cover yourself, and stay there until you feel cool-cold. Natural water sources are ideal. And as for sports clothing, there is no clothing that can improve the heat-loss capability of your skin; donate your money to a worthy charity!</p><img src="https://counter.theconversation.com/content/34489/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nigel Taylor receives funding from the Australian Building Code Board, the Australian Research Council, the Defence Science and Technology Organisation, Fire & Rescue NSW, the National Health & Medical Research Council and the National Roads and Motorists’ Association.</span></em></p>Are neck, hand or forearm cooling, ice-cube sucking or cold showers effective ways to lose heat on those dog days of summer? Can sports clothing keep you cool by wicking away sweat? When the heat is on…Nigel Taylor, Associate Professor of Thermal Physiology, University of WollongongLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/344922015-01-04T19:12:41Z2015-01-04T19:12:41ZHealth Check: do ice cream and cold drinks cool us down?<figure><img src="https://images.theconversation.com/files/67749/original/image-20141219-31049-ze9ewz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An ice cream on a summer's day may hit the spot, but it won't help you beat the heat.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/manc/4272986324">Mark Crossfield/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p>All over the world summer is synonymous with water activities, cold beverages and, of course, ice cream. While most of us agree ice cream and cold beverages are refreshing summer treats, do they actually help cool us down? </p>
<p>To test whether they do, we need to know a bit more about how the body controls temperature in different environments. The process of maintaining an optimal body temperature is called <a href="http://www.ncbi.nlm.nih.gov/pubmed/19137807">thermoregulation</a>, which involves a delicate balance between producing and losing heat. </p>
<p>Humans are warm-blooded or endotherms, which are scientific ways of saying we can control our body temperature independent of the environment. We can do this because our bodies are constantly producing heat as a by-product of internal chemical processes (metabolism). </p>
<h2>How it all works</h2>
<p>Metabolism is necessary to keep our bodies functioning correctly. It includes digestive processes involved in breaking down nutrients in food, the absorption and transportation of those nutrients to the cells, and their conversion into building blocks or energy necessary for physical activity. </p>
<p>The heat this generates is beneficial when it’s cold, but when outside temperatures rise, we need to avoid overheating. While it may seem logical that introducing something cold, like ice cream, into the stomach should help reduce temperature, its initial cooling effect is rapidly replaced by heat generated by digestive processes needed to break down the nutrients in ice cream. Digesting calorie-rich food leads to an increase in body temperature. </p>
<p>So ice cream is not the best option for cooling down, but what about cold beverages? The heat transfer between a cold beverage and the digestive system can directly <a href="http://www.ncbi.nlm.nih.gov/pubmed/24060271">influence temperature</a>. But, this is only momentary and depends on the quantity and caloric content of the ingested liquid. </p>
<p>A small amount of liquid will lose its cooling effect quite quickly as it gets warmed up by the surrounding organs. And large amounts of cold liquids will cause blood flow to slow, making heat transport less effective. </p>
<p>As you can imagine, beverages with a high caloric content, such as soft drinks, will have a similar effect as ice cream and kick start our metabolism shortly after ingestion. </p>
<h2>But I feel cooler…</h2>
<p>The cooling effects of cold liquids are more likely explained by their <a href="http://www.ncbi.nlm.nih.gov/pubmed/24060271">rehydration</a> effects. If heat does build up, the body will attempt to lose excess heat by transporting it away from the vital organs to the skin surface where it is transferred directly to our environment through convection and radiation. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=498&fit=crop&dpr=1 754w, https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=498&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=498&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The cooling effects of cold liquids are more likely explained by their rehydration effects.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/joshlowensohn/4718411987/in/photostream/">Josh Lowensohn/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>For this to occur, the ambient temperature needs to be lower than our own temperature, or the opposite happens and heat will transfer into our body. Just like the heat radiated from the sun on a hot summer day. </p>
<p>Sweating is the most effective way our bodies lose heat. Sweating occurs when an increase in core body temperature is detected by the brain, which responds by stimulating the sweat glands distributed all over the body to produce sweat. </p>
<p>Sweat on the skin surface evaporates, causing the skin to cool down (also called evaporative cooling). Blood that’s flowing close to the surface of the skin gets cooled in the process and helps reduce core temperature. </p>
<p>On average, an adult can lose up to half or one litre of sweat every day, but in hot environments this can increase to almost a litre and a half an hour. That’s why it’s essential to keep the body hydrated during hot weather. </p>
<h2>A different approach</h2>
<p>What about alcoholic beverages? Many people reach for a cold beer on a hot summer day in an attempt to cool down. But alcohol is a diuretic, which means that it will make your body lose water and so reduce your ability to lose heat through sweating. </p>
<p>Surprisingly, warm beverages might be a good way to keep you cool. Although counter intuitive, drinking a warm beverage causes receptors in your mouth and throat to trigger a sweat response, allowing your body to cool down without having to ingest a large amount of the warm liquid.<br>
Active ingredients in <a href="http://www.ncbi.nlm.nih.gov/pubmed/2876434">spicy foods</a> have the same effect; they too trigger a sweat response that allows the body to cool down. That’s why these types of foods are popular in warm climates. </p>
<p>So while cold treats can be satisfying and are certainly refreshing, a better way of cooling down is to spice things up, get your sweat on and, most importantly, rehydrate!</p><img src="https://counter.theconversation.com/content/34492/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter Poortvliet does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>While most of us agree ice cream and cold beverages are refreshing summer treats, do they actually help cool us down?Peter Poortvliet, Post-doctoral Research Fellow in Neuroscience, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.