tag:theconversation.com,2011:/au/topics/hygiene-hypothesis-460/articlesHygiene hypothesis – The Conversation2021-03-09T17:53:40Ztag:theconversation.com,2011:article/1551022021-03-09T17:53:40Z2021-03-09T17:53:40ZA year of COVID-19 lockdown is putting kids at risk of allergies, asthma and autoimmune diseases<figure><img src="https://images.theconversation.com/files/388109/original/file-20210305-19-1pif1gu.jpg?ixlib=rb-1.1.0&rect=353%2C296%2C1628%2C1131&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Children's early interactions with their environment are essential for the immune systems to learn to differentiate between safe versus dangerous disease-causing microbes.</span> <span class="attribution"><span class="source">(CDC/Cade Martin)</span></span></figcaption></figure><p>“Eat dirt!” is a phrase I remember well. It was in the <a href="http://doi.org/10.1056/NEJMe020092">title of an article</a> published by Harvard University environmental health professor, Dr. Scott T. Weiss, and it captured my attention while I was learning about an immunological concept known as the “<a href="https://doi.org/10.1136/bmj.299.6710.1259">hygiene hypothesis</a>.” </p>
<p>The core of the idea is that we live in a microbial world: an environment full of bacteria, parasites, viruses and fungi. And that our interactions with these microbes after birth are extremely important to educate our immune systems to function properly. When we are born, our immune systems are still maturing. </p>
<p>I like the way researchers led by microbiologist Sally F. Bloomfield expressed it in <a href="https://doi.org/10.1177/1757913916650225">their study</a>: </p>
<blockquote>
<p>“The immune system is a learning device, and at birth it resembles a computer with hardware and software but few data. Additional data must be supplied during the first years of life, through contact with micro-organisms from other humans and the natural environment.” </p>
</blockquote>
<p>The immune system has many potent mechanisms for killing pathogens. It <a href="https://www.immunopaedia.org.za/immunology/special-focus-area/6-tolerance-and-autoimmunity/">needs to be carefully regulated</a> to ensure it can eliminate dangerous microbes from the body without causing excessive harm to our own tissues. The interactions we have with our environment early in life are essential for our immune systems to learn to differentiate between safe and dangerous disease-causing microbes. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/388118/original/file-20210305-19-17z17rl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Illustration of different micro-organisms arranged in a circle" src="https://images.theconversation.com/files/388118/original/file-20210305-19-17z17rl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/388118/original/file-20210305-19-17z17rl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=603&fit=crop&dpr=1 600w, https://images.theconversation.com/files/388118/original/file-20210305-19-17z17rl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=603&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/388118/original/file-20210305-19-17z17rl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=603&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/388118/original/file-20210305-19-17z17rl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=758&fit=crop&dpr=1 754w, https://images.theconversation.com/files/388118/original/file-20210305-19-17z17rl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=758&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/388118/original/file-20210305-19-17z17rl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=758&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">We live in a microbial world, an environment full of bacteria, parasites, viruses and fungi.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>Our bodies are covered inside and out with micro-organisms that, under normal circumstances, happily co-habitate with us and promote a healthy immune system. If infants, toddlers and young children are not sufficiently exposed to the microbial world around them, their ability to properly <a href="https://doi.org/10.1038/ni.3829">regulate their own immune systems can be compromised</a>. </p>
<p>To return to the computer analogy, the data that gets uploaded into the software are incomplete. This lack of data can cause the immune system to struggle to differentiate between what is truly dangerous and should be eliminated, and what is not dangerous and should not be responded to. In plain terms, this scenario can <a href="https://doi.org/10.1038/ni.3829">promote allergies</a>, <a href="https://www.fda.gov/vaccines-blood-biologics/consumers-biologics/asthma-hygiene-hypothesis">asthma</a> and <a href="https://doi.org/10.1038/nri.2017.111">autoimmune diseases</a>.</p>
<h2>Concrete jungles</h2>
<p>Scientists are moving away from using the term “hygiene hypothesis” because it could be misinterpreted as meaning that hygiene is not good for a developing immune system. This is not true, nor should anybody advocate for actually eating dirt to gain exposure to microbes. Moderation and targeted hygiene would be best. </p>
<figure class="align-left ">
<img alt="Two children on a windowsill looking outside at a tall building." src="https://images.theconversation.com/files/388220/original/file-20210308-13-j004bb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/388220/original/file-20210308-13-j004bb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/388220/original/file-20210308-13-j004bb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/388220/original/file-20210308-13-j004bb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/388220/original/file-20210308-13-j004bb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/388220/original/file-20210308-13-j004bb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/388220/original/file-20210308-13-j004bb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">By keeping children isolated and indoors, most COVID-19 policies have maximized the potential for children to develop dysregulated immune systems.</span>
<span class="attribution"><span class="source">(Pexels/Jessica West)</span></span>
</figcaption>
</figure>
<p>Specifically, we need to practise proper hygiene in the context of trying to prevent infectious diseases, but still allow our immune systems to interact with safe and essential microbes. Many middle-income countries have seen an <a href="https://doi.org/10.1016/j.jaci.2015.03.048">epidemic</a> of allergic diseases over the past several decades. This is, in part, due to increased <a href="http://dx.doi.org/10.1136/thx.52.2.161">urbanization</a> which is akin to living in “concrete jungles” with reduced exposure to the natural environment. </p>
<p>Societies have also adopted behaviours that <a href="https://doi.org/10.1111/j.1365-2222.2006.02463.x">limit exposure</a> to microbes. The overuse of <a href="http://doi.org/10.1126/scitranslmed.aad7121">antibiotics</a> exacerbates the problem by non-discriminately eliminating good microbes along with bad ones.</p>
<p>Bloomfield and her team of microbiology researchers came to some important conclusions in their study:</p>
<blockquote>
<p>“Evidence suggests a combination of strategies, including … increased social exposure through sport, other outdoor activities, less time spent indoors … may help … reduce risks of allergic disease. Preventive efforts must focus on early life.”</p>
</blockquote>
<p>Now think about <a href="https://www.cbc.ca/news/canada/toronto/ontario-shutdown-details-pdf-1.5850224">government-led responses</a> to <a href="https://www.who.int/emergencies/diseases/novel-coronavirus-2019/technical-guidance/naming-the-coronavirus-disease-(covid-2019)-and-the-virus-that-causes-it">COVID-19</a>, which was <a href="https://www.who.int/director-general/speeches/detail/who-director-general-s-opening-remarks-at-the-media-briefing-on-covid-19---11-march-2020">declared a pandemic by the World Health Organization</a> on March 11, 2020. The lockdown and restriction policies that have been enacted to help prevent the spread of COVID-19 contradict the recommendations to ensure proper immunological development in children. </p>
<p><a href="http://doi.org/10.1001/jamanetworkopen.2020.20495">Data suggest that SARS-CoV-2</a> does not represent a greater danger to children than the <a href="https://www.cdc.gov/flu/season/faq-flu-season-2020-2021.htm">annual flu</a>. Yet <a href="https://theconversation.com/trapped-at-home-during-the-coronavirus-pandemic-heres-how-parents-can-get-through-challenging-moments-154166">social interactions of children have been severely limited</a>, including removing them from schools. Most of their extracurricular activities have been cancelled and they have been discouraged from leaving their homes. Even the air they breathe is often <a href="https://www.ctvnews.ca/health/coronavirus/back-to-school-shopping-amid-covid-19-what-you-need-for-september-1.5080910">filtered by masks and there is prevalent use of hand sanitizer</a>. </p>
<h2>Compromised immunological development</h2>
<p>In short, most COVID-19 policies have maximized the potential for children to develop dysregulated immune systems. As a viral immunologist, I was not overly concerned about this in the early stages of the pandemic when “temporary” measures were put in place to “<a href="https://www.uab.edu/news/youcanuse/item/11268-what-exactly-does-it-mean-to-flatten-the-curve-uab-expert-defines-coronavirus-terminology-for-everyday-life">flatten the curve</a>.” </p>
<p>However, there is cause for concern one year later, after many places in Canada and other countries have spent months in lockdowns or with very limited social contact and activities to prevent the spread of COVID-19. </p>
<p>The youngest among us have had their immunological development compromised for one year and growing. The more immature the immune system is, the more prone it will be to becoming dysregulated during the pandemic. </p>
<figure class="align-center ">
<img alt="An empty swing in an empty playground" src="https://images.theconversation.com/files/388222/original/file-20210308-24-t9jq1e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/388222/original/file-20210308-24-t9jq1e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/388222/original/file-20210308-24-t9jq1e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/388222/original/file-20210308-24-t9jq1e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/388222/original/file-20210308-24-t9jq1e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/388222/original/file-20210308-24-t9jq1e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/388222/original/file-20210308-24-t9jq1e.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 policies that have been enacted to help prevent the spread of COVID-19 contradict the recommendations to ensure proper immunological development in children.</span>
<span class="attribution"><span class="source">(Unsplash/Markus Spiske)</span></span>
</figcaption>
</figure>
<p>For example, the problem would likely be more prevalent in infants than toddlers. Although the <a href="https://doi.org/10.3389/fimmu.2017.00957">human immune system is largely mature</a> by approximately age six, some important components are still developing into adolescence. As such, the only people who can be certain that current isolation policies will have no negative impact on their immune system’s ability to self-regulate are adults. </p>
<p>An unfortunate and under-appreciated long-term legacy of this pandemic will likely be a cluster of “pandemic youth” that grow up to suffer higher-than-average rates of allergies, asthma and autoimmune diseases. This will hold true for children in all countries that enacted isolation policies. </p>
<p>Interestingly, it has been noted that the new <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/mrna.html">messenger RNA-based COVID-19 vaccines</a> that are packaged inside liposome nanoparticles <a href="http://doi.org/10.1126/science.abg2359">might be contraindicated</a> for some individuals with a propensity towards severe allergic responses. Ironically, we may be setting up many of our youth to develop hypersensitivities to this vaccine technology when they are older.</p>
<p>Raising children during the pandemic has largely occurred in isolated/sanitized environments that are unprecedented in extent and duration. These kids are at greater risk of developing hypersensitivities and autoimmune diseases than anyone before them. The immune systems of children are not designed to develop in isolation from the microbial world, so let’s consider letting children be children again.</p><img src="https://counter.theconversation.com/content/155102/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr. Byram W. Bridle has received funding from the following government agencies to support his research program: Canadian Institutes of Health Research, Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, Ontario COVID-19 Rapid Research Funding, National Research Council of Canada – Pandemic Response Challenge Program.
</span></em></p>COVID-19 prevention measures are at odds with guidelines for healthy development of children’s immune systems. The result may be a cluster of youth with more allergies, asthma and autoimmune disease.Byram W. Bridle, Associate Professor of Viral Immunology, Department of Pathobiology, University of GuelphLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1436902020-08-07T04:42:11Z2020-08-07T04:42:11ZNo, the extra hygiene precautions we’re taking for COVID-19 won’t weaken our immune systems<figure><img src="https://images.theconversation.com/files/351202/original/file-20200805-118-1ioumlr.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5996%2C4002&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>During the COVID-19 pandemic we’re constantly being reminded to <a href="https://www.health.gov.au/news/health-alerts/novel-coronavirus-2019-ncov-health-alert/how-to-protect-yourself-and-others-from-coronavirus-covid-19/good-hygiene-for-coronavirus-covid-19">practise good hygiene</a> by frequently washing our hands and regularly cleaning the spaces where we live and work.</p>
<p>These practices aim to remove or kill the coronavirus that causes COVID-19, and thereby minimise our risk of infection.</p>
<p>But there have been some suggestions using hand sanitiser and practising other hygiene measures too often could <a href="https://www.womenshealthmag.com/health/a32464311/does-hand-sanitizer-weaken-immune-system/">weaken our immune system</a>, by reducing our body’s exposure to germs and with it the chance to “train” our immune defences.</p>
<p>The good news is, there’s no evidence to suggest this will be the case.</p>
<h2>The ‘hygiene hypothesis’</h2>
<p>For healthy immune function, it’s important we’re exposed to a diverse range of bugs in the environment, known as microbes. Most of these don’t make us sick.</p>
<p>The belief that a high level of cleaning and personal hygiene weakens our immune system is a common interpretation of what’s called the “<a href="https://pubmed.ncbi.nlm.nih.gov/29034905/">hygiene hypothesis</a>”.</p>
<p>The <a href="https://www.pnas.org/content/114/7/1433">hygiene hypothesis</a> is a theory that suggests a young child’s environment can be “too clean”, and they won’t be exposed to enough of these microbes to effectively stimulate their immune system as it develops.</p>
<p>The argument is that this results in increased allergies, asthma and certain autoimmune disorders. But scientists have refuted this hypothesis <a href="https://search.proquest.com/openview/1c0bbcc234be0e229473dc1bdf9960b0/1?pq-origsite=gscholar&cbl=2043523">in recent years</a>, as research has shown there are multiple other reasons for the increased incidence of these conditions.</p>
<p>Importantly, <a href="https://theconversation.com/if-being-too-clean-makes-us-sick-why-isnt-getting-dirty-the-solution-50572">being too dirty</a> doesn’t help our immune system either. It generally makes inflammation worse. </p>
<figure class="align-center ">
<img alt="A young girl plays in the mud." src="https://images.theconversation.com/files/351676/original/file-20200807-16-1r4q2k1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/351676/original/file-20200807-16-1r4q2k1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/351676/original/file-20200807-16-1r4q2k1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/351676/original/file-20200807-16-1r4q2k1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/351676/original/file-20200807-16-1r4q2k1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/351676/original/file-20200807-16-1r4q2k1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/351676/original/file-20200807-16-1r4q2k1.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 ‘hygiene hypothesis’ has been controversial.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>What is the immune system?</h2>
<p>The <a href="https://www.livescience.com/38028-how-the-human-body-s-immune-system-works-infographic.html">immune system</a> works to protect our bodies against things that threaten to make us sick — from harmful chemicals, to bacteria and viruses, to cancer cells.</p>
<p>It’s made up of <a href="https://www.medicalnewstoday.com/articles/320101#white-blood-cells">two lines of defence</a>. The first is the “innate” immune system, which responds rapidly to a range of pathogens to fight infection and prevent tissue damage. </p>
<p>Next is the “adaptive” immune system, made up of immune cells that develop a more targeted or specific response to fight off harsher germs such as viruses. Adaptive immune cells work by recognising small parts of the virus on the outside of the infected cell (for example, lung cells), and destroying them. </p>
<p>These cells then become what we call “memory cells”. The next time they encounter the same virus, they can eliminate it straight away. </p>
<p>This development of the immune system starts after birth and <a href="https://medlineplus.gov/ency/article/004008.htm">declines</a> in old age. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/5-ways-nutrition-could-help-your-immune-system-fight-off-the-coronavirus-133356">5 ways nutrition could help your immune system fight off the coronavirus</a>
</strong>
</em>
</p>
<hr>
<h2>What can weaken our immune system?</h2>
<p>Some aspects of our modern lifestyle can weaken our immune system. These include:</p>
<ul>
<li><p>a <a href="https://theconversation.com/sleep-wont-cure-the-coronavirus-but-it-can-help-our-bodies-fight-it-134674">lack of sleep</a></p></li>
<li><p>certain medications and the <a href="https://www.insider.com/do-antibiotics-weaken-the-immune-system#:%7E:text=If%20your%20doctor%20prescribes%20antibiotics,overuse%20leads%20to%20antibiotic%20resistance.">overuse of antibiotics</a> </p></li>
<li><p>low <a href="https://theconversation.com/does-vitamin-d-protect-against-coronavirus-138001">vitamin D levels</a></p></li>
<li><p>a Western diet rich in <a href="https://theconversation.com/while-we-wait-for-a-coronavirus-vaccine-eating-well-exercising-and-managing-stress-can-boost-your-immune-system-137255">processed foods</a>, and reduced consumption of <a href="https://theconversation.com/5-ways-nutrition-could-help-your-immune-system-fight-off-the-coronavirus-133356">fruits and vegetables</a></p></li>
<li><p>a lack of <a href="https://www.webmd.com/balance/ss/slideshow-healthy-actions-feel-better">physical activity</a></p></li>
<li><p><a href="https://theconversation.com/while-we-wait-for-a-coronavirus-vaccine-eating-well-exercising-and-managing-stress-can-boost-your-immune-system-137255">stress</a> and anxiety. </p></li>
</ul>
<figure class="align-center ">
<img alt="Woman holds healthy breakfast bowl with blueberries, guava and cereal." src="https://images.theconversation.com/files/351689/original/file-20200807-20-n3mem1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/351689/original/file-20200807-20-n3mem1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=444&fit=crop&dpr=1 600w, https://images.theconversation.com/files/351689/original/file-20200807-20-n3mem1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=444&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/351689/original/file-20200807-20-n3mem1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=444&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/351689/original/file-20200807-20-n3mem1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=558&fit=crop&dpr=1 754w, https://images.theconversation.com/files/351689/original/file-20200807-20-n3mem1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=558&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/351689/original/file-20200807-20-n3mem1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=558&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A healthy diet is one way to support immune function.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>But there’s no scientific evidence to support the notion that extra hygiene precautions will weaken our immune system or leave us more <a href="https://www.reuters.com/article/uk-factcheck-hand-sanitizer-bacteria/false-claim-overuse-of-hand-sanitizers-and-bacterial-infections-overuse-of-face-masks-weakens-the-immune-system-idUSKBN22R2MV">susceptible to infection</a> by bacteria or viruses.</p>
<p>Microbes are <a href="https://www.mayoclinic.org/diseases-conditions/infectious-diseases/in-depth/germs/art-20045289">everywhere</a>: in the air, on food, and in plants, animals, soil and water. They can be found on just about every surface, including inside and outside your body. </p>
<p>The hygiene measures recommended during COVID-19 will help curb the spread of the coronavirus and greatly reduce our risk of infection — but won’t eliminate all microbes from our lives.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/from-hospitals-to-households-we-can-all-be-better-at-remembering-to-wash-our-hands-141271">From hospitals to households, we can all be better at remembering to wash our hands</a>
</strong>
</em>
</p>
<hr>
<h2>Keep it clean</h2>
<p><a href="https://www.safeworkaustralia.gov.au/covid-19-information-workplaces/cleaning-prevent-spread-covid-19">Cleaning</a> refers to the removal of microbes, dirt and impurities from surfaces. It doesn’t kill microbes, but by removing them, it lowers their numbers and therefore reduces the risk of spreading infection.</p>
<p>In contrast, <a href="https://simplegreen.com/news-and-media/disinfecting-dwell-time/">disinfecting</a> refers to using chemicals, known as disinfectants, to kill microbes on surfaces. </p>
<p>A combination of cleaning and disinfecting is the most effective way to get rid of microbes such as coronavirus.</p>
<figure class="align-center ">
<img alt="A colourful bucket of cleaning products, with a woman mopping in the background." src="https://images.theconversation.com/files/351691/original/file-20200807-24-3m9b77.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/351691/original/file-20200807-24-3m9b77.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/351691/original/file-20200807-24-3m9b77.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/351691/original/file-20200807-24-3m9b77.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/351691/original/file-20200807-24-3m9b77.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/351691/original/file-20200807-24-3m9b77.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/351691/original/file-20200807-24-3m9b77.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">Cleaning removes microbes and lowers the risk an infection will spread.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Extra <a href="https://www.health.gov.au/news/health-alerts/novel-coronavirus-2019-ncov-health-alert/how-to-protect-yourself-and-others-from-coronavirus-covid-19/good-hygiene-for-coronavirus-covid-19">hand hygiene</a> is of course one of the <a href="https://www2.health.vic.gov.au/public-health/infectious-diseases/infection-control-guidelines/standard-additional-precautions">most important infection control</a> measures.</p>
<p>We’ve been advised to clean our hands with soap and water for at least 20 seconds. If this is not possible, use hand sanitiser with at least <a href="https://www.cdc.gov/coronavirus/2019-ncov/hcp/hand-hygiene.html">60% ethanol or 70% isopropanol</a>. </p>
<p>Frequent hand-washing, especially if a sanitiser is used, can disrupt the <a href="https://www.popsci.com/is-hand-sanitizer-bad-for-my-microbiome/">natural skin biome</a>, which can lead to increased skin infections. This can be managed with the use of moisturisers. </p>
<p>But the extra hygiene measures during COVID-19 won’t weaken our immune systems. On the contrary, they are vital in controlling the pandemic. </p>
<p>If you’re worried about your immune system, don’t stop washing your hands or keeping your house clean. Importantly, follow a healthy balanced diet, do regular exercise and look after your mental health.</p>
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Read more:
<a href="https://theconversation.com/how-to-clean-your-house-to-prevent-the-spread-of-coronavirus-and-other-infections-133912">How to clean your house to prevent the spread of coronavirus and other infections</a>
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<img src="https://counter.theconversation.com/content/143690/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Vasso Apostolopoulos has received funding and fellowships from NHMRC of Australia. </span></em></p><p class="fine-print"><em><span>Maximilian de Courten has received funding from the NHMRC of Australia in the past. </span></em></p><p class="fine-print"><em><span>Maja Husaric 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>We’re cleaning and washing our hands perhaps more than we ever have before. But suggestions that all this this extra hygiene could weaken our immune systems are unfounded.Vasso Apostolopoulos, Pro Vice-Chancellor, Research Partnerships, Victoria UniversityMaja Husaric, Lecturer; MD, Victoria UniversityMaximilian de Courten, Health Policy Lead and Professor in Global Public Health at the Mitchell Institute, Victoria UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/791162017-07-03T20:08:20Z2017-07-03T20:08:20ZEssays on health: microbes aren’t the enemy, they’re a big part of who we are<figure><img src="https://images.theconversation.com/files/176532/original/file-20170703-751-b3kd8o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Modern diets are changing the compositions of our gut microbiota, and with that, our personalities.</span> <span class="attribution"><span class="source">from shutterstock.com</span></span></figcaption></figure><p>We have long believed that “good” immune cells recognise and defend against “bad” invaders. That’s why a large proportion of medicine has been directed at killing microbial enemies and conquering microbial infections. </p>
<p>This militaristic understanding of immunity reflected the culture of the 20th century, which was dominated by nation building and world wars between “us” and “them.” It was a time when “survival of the fittest” came to be seen as the driver of evolution and competition and war were considered a natural part of what it is to be human.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/176159/original/file-20170629-6546-1dm1dn9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/176159/original/file-20170629-6546-1dm1dn9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/176159/original/file-20170629-6546-1dm1dn9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=581&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176159/original/file-20170629-6546-1dm1dn9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=581&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176159/original/file-20170629-6546-1dm1dn9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=581&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176159/original/file-20170629-6546-1dm1dn9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=730&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176159/original/file-20170629-6546-1dm1dn9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=730&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176159/original/file-20170629-6546-1dm1dn9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=730&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">There are millions of microorganisms in our gut.</span>
<span class="attribution"><span class="source">from shutterstock.com</span></span>
</figcaption>
</figure>
<p>But a radical shift in understanding the relationship between humans and microorganisms occurred with the discovery that only <a href="http://www.biorxiv.org/content/early/2016/01/06/036103">50% of the cells in our bodies are human</a>. The rest are microbes, such as bacteria, yeasts (members of the fungus family), viruses, and even insects. Together, these make up the microbiome.</p>
<p>The 23,000 genes that comprise the human genome pale in comparison with the <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1753-4887.2012.00493.x/abstract">3.3 million genes</a> in the microbes that live in our guts. These produce proteins that help us digest food and support our immune systems. </p>
<p>Through the gut-brain axis, these genes even <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4259177/">influence mood and memory</a>. The gut-brain axis is a set of communication pathways between the gut and brain occurring largely through the actions of the gut microbiome.</p>
<p>Because we have evolved with microorganisms inside us, we now have specialised communities in our guts, on our skin, and in our mouths. Our microbes are understood to be so critical to our existence, <a href="http://www.publish.csiro.au/ma/pdf/MA15005">many scientists</a> consider us to be symbiotic organisms, made up of the host, the microbiome and the environment. This holy trinity is what they call the “holobiont”. </p>
<p>Considering human life as a function of the microbiome and our environment allows us to acknowledge that we may be affected by entities that harbour different evolutionary needs. For example, our food choices don’t just affect human health through nutrients and caloric balance, but also through their impacts on the gut microbiome.</p>
<h2>Microbes and diet</h2>
<p>The food we eat feeds our gut microbes and directly impacts their survival. Within two days of changing diet, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3957428/">our gut species change</a>. Different gut bacteria thrive on different diets. For instance, <em>Prevotella</em> strains consume carbohydrates while <em>Bacteroidetes</em> prefer some fats, and <em>Candida</em> prefer glucose over protein. So, some species starve and others thrive based on what we eat.</p>
<p>The species in ours guts are also proving to be relevant to health and disease. <em>Prevotella</em>, for instance, has been <a href="http://www.sciencedirect.com/science/article/pii/S1550413115005173#undfig1">linked to improved glucose tolerance</a> and is much more prevalent in the guts of <a href="https://www.nature.com/articles/ncomms4654?WT.ec_">hunter-gatherer societies</a> (such as the Hadza people in Tanzania) than those in Western societies. The reduction of <em>Prevotella</em> in gut-bacteria in Western populations is thought to partially explain modern epidemics such as diabetes and obesity. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/176533/original/file-20170703-751-t7q3vu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/176533/original/file-20170703-751-t7q3vu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/176533/original/file-20170703-751-t7q3vu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176533/original/file-20170703-751-t7q3vu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176533/original/file-20170703-751-t7q3vu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176533/original/file-20170703-751-t7q3vu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176533/original/file-20170703-751-t7q3vu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176533/original/file-20170703-751-t7q3vu.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">The Hadza people of Tanzania have a much higher prevalence of glucose-tolerating Prevotella bacteria in their guts than those in Western societies.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/woodlouse/3990736265/in/photolist-75DyRF-25aGVc-75HnHQ-bsmuJX-8qR7Jy-8qR9q3-bsmf9R-pixAaV-8qR1Af-8qR2ZQ-8qMWtt-8qQXah-8qQYs5-bsmvjn-8qR8wS-8qR5vW-8qQWy3-8qMYRn-75Hmyo-8qMST6-bsmqkc-5USDw8-bsmnVe-8qMZxz-bsmpHP-bsm7ov-5UX4so-8qR4BL-5UWV3u-5USuFK-5USqw2-bsmtAP-5USrkr-5UWS1J-5UWX6W-5USFjK-bsmt3X-bsmycg-bsmdop-bsmeET-5UWW4A-bsmuqH-5UWMEY-bsm8AV-5USB3F-bsmmHT-bsm6kk-5USpd4-bsmvPt-5UWYTS">Woodlouse/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>It shouldn’t surprise us then, that microbes can shape our food choices to ensure their own survival. Some metabolites, the small byproducts of microbial digestion, can make us feel hungry, full or crave certain foods. However, the evidence in humans is so far somewhat circumstantial. A study of chocolate-craving and chocolate-indifferent people <a href="http://pubs.acs.org/doi/abs/10.1021/pr070431h">found different microbial metabolites</a> in their urine, suggesting different bacteria were present in the gut. </p>
<p>Metabolites are important in terms of function, because we know these can send signals to the brain. Signals to regulate eating behaviour are also transmitted via the vagus nerve that runs between the brain and the gut. At least two human studies have shown <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4270213/">blocking the vagus nerve</a> induces weight loss in obesity, while <a href="https://www.ncbi.nlm.nih.gov/pubmed/7030452">stimulating it in rats has led to overeating</a>. </p>
<h2>Microbes and behaviour</h2>
<p>Behaviour is also a function of the holobiont, not just the human host. Some metabolites are neuroactive, which means they can travel along the gut–brain axis and affect human mood, mental health and behaviour. </p>
<p>Much of the work exploring direct microbe-related behaviour has been done in mice and rats. These studies have had some pretty interesting results though. They’ve shown that <a href="http://www.sciencedirect.com/science/article/pii/S0022395616301571">behaviour can be transferred through poo transplants</a>, that animals bred without any bacteria show <a href="https://www.ncbi.nlm.nih.gov/pubmed/21054680">unusual social and emotional behaviours</a>, and that serotonin - the brain chemical associated with mood and depression - is <a href="https://www.ncbi.nlm.nih.gov/pubmed/26805875">produced largely in the gut</a>. Together, these findings indicate a strong evidence base for the fact that the microbiome can affect host behaviour. </p>
<p>The best human evidence comes from the observed impacts of food on mood and behaviour – and microbes are the likely explanation. A good example is a study of healthy women <a href="http://www.sciencedirect.com/science/article/pii/S0016508513002928">some of whom consumed yogurt with a certain probiotic</a> for one month. The researchers had the participants lie in a functional MRI scanner while they were shown pictures of faces with different emotions. </p>
<p>Those who had received the yogurt had reduced activity in the emotional processing brain regions, suggesting a dampening of the stress response, than those who didn’t have yogurt.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/176530/original/file-20170703-751-cpnsxx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/176530/original/file-20170703-751-cpnsxx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/176530/original/file-20170703-751-cpnsxx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176530/original/file-20170703-751-cpnsxx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176530/original/file-20170703-751-cpnsxx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176530/original/file-20170703-751-cpnsxx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176530/original/file-20170703-751-cpnsxx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176530/original/file-20170703-751-cpnsxx.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">Research suggests the gut microbiome may have a role in the development of autism spectrum disorders (ASD).</span>
<span class="attribution"><span class="source">from shutterstock.com</span></span>
</figcaption>
</figure>
<p>The protective value of a <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0087657">whole-food diet for depression</a> also points to the importance of gut microbes for brain health. Mood disorders that can accompany conditions such as irritable bowel syndrome and inflammatory bowel diseases are thought to be related to <a href="http://onlinelibrary.wiley.com/doi/10.1111/nmo.12198/full">microbial disruption in the bowel</a>. </p>
<p>Recent research has also suggested the gut microbiome may have a role in the development of autism spectrum disorders (ASD). Research has found people with ASD have <a href="https://link.springer.com/article/10.1007/s11046-015-9949-3">significantly higher numbers</a> of <em>Candida</em> species in their intestines, for instance. Although determining causation is complicated, these microbes reduce the absorption of carbohydrates and release ammonia and other toxins which are thought to contribute to autistic behaviours. </p>
<p>There is also <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4342262/">emerging evidence</a> showing that differences in gut bacteria in children are related to behavioural problems, and potentially to future mental health risk. </p>
<p>There are <a href="https://www.ncbi.nlm.nih.gov/pubmed/26372511">numerous reports</a> of changed gut bacteria in people experiencing mental illness such as schizophrenia and depression, as well as neurological disorders such as Parkinson’s disease. However, it is difficult to establish causation. </p>
<p>A compelling argument is made by studies that show microbiota transplants from people to mice actually change the behaviour of the recipient mice. <a href="http://www.the-scientist.com/?articles.view/articleNo/48678/title/Human-Gut-Microbe-Transplant-Alters-Mouse-Behavior/">One study</a> used microbiota from people experiencing irritable bowel syndrome (IBS) and showed the mice who received the transplants experienced the same anxious behaviour that often accompanies IBS.</p>
<h2>Changing the game</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/176171/original/file-20170629-31297-26d3bu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/176171/original/file-20170629-31297-26d3bu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/176171/original/file-20170629-31297-26d3bu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176171/original/file-20170629-31297-26d3bu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176171/original/file-20170629-31297-26d3bu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176171/original/file-20170629-31297-26d3bu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176171/original/file-20170629-31297-26d3bu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176171/original/file-20170629-31297-26d3bu.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"></a>
<figcaption>
<span class="caption">Many of our microbes aren’t good or bad, but they become bad because we change the game.</span>
<span class="attribution"><span class="source">from shutterstock.com</span></span>
</figcaption>
</figure>
<p>We are ecosystems, whose members are intricately balanced by cooperation and competition. Many of our microbes are neither good nor bad. But they become bad because we change the game, giving them the opportunity to be bad.</p>
<p>For example, we are increasingly interfering in the ecosystem by using antibiotics and sanitisers, hormone and immune system treatments, cosmetic and plastic surgery, or biomedical implants and devices such as contact lenses or heart valves. </p>
<p>Although sanitation and nutrition have greatly improved in much of the world, antibiotic overuse has led to the rise of <a href="https://theconversation.com/antibiotic-resistance-sorry-not-my-problem-44011">antibiotic resistant bacteria</a>. Antibiotics also change what is in our microbiome. Many women would be familiar with <em>Candida</em> infections (thrush) that <a href="http://jcm.asm.org/content/44/9/3213.short">flourish after they use antibiotics</a>, for instance.</p>
<p>Biomedical implants, contact lenses and dentures provide warm, moist and nutritious conditions for colonisation by microbes. Increased oestrogen use in birth control pills and other hormone treatments has been shown to <a href="https://www.termedia.pl/Journal/-10/Streszczenie-20833">promote yeast infection</a> and reduce immune efficiency. </p>
<p>In fact, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2841828/">the hygiene hypothesis</a> argues that infections help build our immune system and the proliferation of sanitising disinfectants in our homes could be contributing to skin allergies and respiratory conditions.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/176560/original/file-20170703-7743-j2m8km.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/176560/original/file-20170703-7743-j2m8km.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/176560/original/file-20170703-7743-j2m8km.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176560/original/file-20170703-7743-j2m8km.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176560/original/file-20170703-7743-j2m8km.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176560/original/file-20170703-7743-j2m8km.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1130&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176560/original/file-20170703-7743-j2m8km.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1130&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176560/original/file-20170703-7743-j2m8km.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1130&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Body odours aren’t inherently unhealthy.</span>
<span class="attribution"><span class="source">from shutterstock.com</span></span>
</figcaption>
</figure>
<p>Our definitions of good and bad are cultural as much as biological. For example, body odours and stale breath which are caused by microbes are not inherently unhealthy, but the market for antiperspirants, deodorisers and mouthwash is flourishing. Increasing skin conditions, allergies and illness could be the result of our attempts to control and groom our microbes, good and bad. </p>
<p>Our diets have also changed rapidly and the flow–on changes to both human and microbial health are apparent. Non–communicable disease epidemics such as obesity and heart disease are clear consequences of <a href="http://www.who.int/mediacentre/factsheets/fs355/en/">highly processed foods and increasingly inactive lifestyles</a>. </p>
<p>The changing modern diet may also have effects over generations, as we pass on our microbial communities to our children. Research in mice has found some <a href="http://www.nature.com/nature/journal/v529/n7585/full/nature16504.html">bacterial strains could not recover</a> in the grandchildren of mice fed low–fibre western diets, even when a high–fibre diet was reintroduced. It may not be long then, before the modern western diet will have irrevocably changed the gut bugs and health of future humans.</p>
<h2>Rethinking the metaphor</h2>
<p>For most of the twentieth century, we were at war with microbes. Vigilant immune systems defended against vicious and sneaky microbial attacks. The cold and flu medication Codral, as just one example, famously helped us “<a href="https://www.youtube.com/watch?v=4Dk60kWcP8o">soldier on</a>.”</p>
<p>We have to rethink this militaristic metaphor. If we are a complex ecosystem which relies on the microbes in it, we cannot wage war against them. If microbes are part of our immune systems, who is fighting whom?</p>
<p>How we <a href="http://iai.asm.org/content/83/1/2.abstract">talk about our microbes</a> reflects how we think about ourselves and others. As holobionts, we need to figure out how to live with all the members of our bodies. How might our worlds (and bodies) be different if we behave as resilient communities where the “others” are different selves, rather than invaders, terrorists, colonisers, or competitors?</p>
<hr>
<p><em>The authors will be presenting on this topic at the upcoming Emerging Issues in Science and Society event at <a href="http://www.deakin.edu.au/adi/our-research/research-networks/science-and-society-network">Deakin University</a> on Thursday, 6 July 2017. For more information and to book tickets, see the event’s <a href="https://www.eventbrite.com.au/e/emerging-issues-in-science-and-society-registration-33136207288">website</a>.</em></p><img src="https://counter.theconversation.com/content/79116/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tarsh Bates is affiliated with SymbioticA, The University of Western Australia. </span></em></p><p class="fine-print"><em><span>Amy Loughman 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>For most of the twentieth century, we were at war with microbes, leading to substantial changes in our body’s ecosystem. This has changed our diets, disease profile, moods and even personalities.Amy Loughman, Senior Research Fellow, Deakin UniversityTarsh Bates, PhD candidate, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/666472016-10-10T10:53:55Z2016-10-10T10:53:55ZIs it safe to wash my hands, doctor?<figure><img src="https://images.theconversation.com/files/140750/original/image-20161006-32691-aau60t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">There are downsides to clean hands.
</span> <span class="attribution"><span class="source"> ProStockStudio</span></span></figcaption></figure><p>A battle is waging about how often and how carefully we should wash our hands. Many allergy experts say it is vital for our future health and that of our children to reduce hand washing and allow friendly microbes back into our mouths. Some authors go as far as <a href="https://www.theguardian.com/lifeandstyle/2016/sep/24/snap-crackle-and-filth-let-kids-eat-dirt">urging us to eat dirt</a>. But other experts, such as those working on infectious diseases, say this is highly irresponsible and dangerous advice because of the recent rise in cases of food poisoning and transmission of viruses.</p>
<p>So, who is correct? We desperately need some sensible guidance.</p>
<p>Allergies have been rising since the 1970s in all developed countries and problems caused by previously harmless pollen, house dust mites and various foods are reaching epidemic proportions. Remarkably, while the first case of a documented food allergy was reported only in 1969, nut-free schools are now commonplace. Originally, <a href="http://onlinelibrary.wiley.com/doi/10.1111/all.12423/full">we were told to deal</a> with allergies by eliminating or avoiding them – vacuuming, disinfecting, removing pets, restricting diets and staying indoors. But this has done nothing to stop rates rising. </p>
<h2>The hygiene hypothesis</h2>
<p>Some 25 years ago, <a href="http://thorax.bmj.com/content/55/suppl_1/S2">a paper</a> suggested a different mechanism to explain allergy – which has since been called the “hygiene hypothesis”. It discovered that children in large, poor families living in rural farms, surrounded by animals and dust, had less allergies. These findings have been replicated multiple times around the world in different environments. Children from small families in rich, urban neighbourhoods are consistently found to have the highest allergy rates.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/140753/original/image-20161006-32727-1pkmi7z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/140753/original/image-20161006-32727-1pkmi7z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/140753/original/image-20161006-32727-1pkmi7z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/140753/original/image-20161006-32727-1pkmi7z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/140753/original/image-20161006-32727-1pkmi7z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/140753/original/image-20161006-32727-1pkmi7z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/140753/original/image-20161006-32727-1pkmi7z.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"></span>
<span class="attribution"><span class="source">Mladen Mitrinovic</span></span>
</figcaption>
</figure>
<p>The initial idea was that children exposed early on to pathogens must have better tuned immune systems, which don’t overreact when later exposed to harmless proteins like pollen or peanuts. However a mechanism for this was never proven and recent scientific breakthroughs suggests the infections themselves <a href="https://www.ncbi.nlm.nih.gov/pubmed/?term=Bloomfield+SF+2016">may not be the main story</a>.</p>
<p>Instead, the realisation that the functioning of our immune system is totally dependent on the normal inhabitants of our guts – in particular the 100 trillion microbes in our colon (known as the microbiome) – has changed our view of hygiene. These microbes <a href="https://www.ncbi.nlm.nih.gov/pubmed/27383981">are key</a> to digesting food and producing vitamins and chemicals that keep our immune system in check. When our normal microbiome gets disturbed, we lose species diversity and this makes us prone to an inappropriate response to harmless proteins – and allergies and autoimmune diseases ensue.</p>
<p>This has happened over the last 30 to 40 years in developed countries due to a deadly combination of events that disrupt microbes – <a href="http://www.theatlantic.com/health/archive/2015/11/taking-antibiotics-can-change-the-gut-microbiome-for-up-to-a-year/415875/">antibiotic overuse</a>, <a href="http://www.nytimes.com/2013/05/19/magazine/say-hello-to-the-100-trillion-bacteria-that-make-up-your-microbiome.html">processed sterile diets</a>, <a href="http://advances.nutrition.org/content/4/1/16.full">reduced fibre intakes</a>, reduced <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4464665/">breast feeding and high caesarean section rates</a>. We are estimated to have 40% less gut and mouth microbial species diversity than <a href="https://www.ncbi.nlm.nih.gov/pubmed/27624970">hunter gatherers</a> and <a href="https://www.ncbi.nlm.nih.gov/pubmed/23416520">pre-medieval people</a>. This is compounded by trends of increasing urban living moving us ever further away from our natural outdoor environment of dust, animals and soil.</p>
<h2>How dangerous is dirt?</h2>
<p>So is not washing your hands the answer? It will certainly increase transmission of microbes between people. And, although unproven, it could increase gut diversity and health. But clearly this is very unwise for high-risk individuals such as the elderly or immune deficient – or during a norovirus outbreak or in environments such as hospitals. </p>
<p>There is also no reason to alter advice and habits on good toilet hygiene. Some people believe that transmission of cold and flu viruses could be reduced by regular hand washing – <a href="https://www.ncbi.nlm.nih.gov/pubmed/27383981">but the data is inconclusive</a> and could be offset by the reduced immunity to viral infections caused by a potentially reduced microbiome. Still, if you are a professional food worker, hand hygiene is vital and we still have fatal <a href="http://www.connexionfrance.com/-chain-Quick-sales-slump-after-Avignon-food-poisoning-death-manslaughter-12544-view-article.html">outbreaks from fast-food</a> and to remind us. </p>
<p>The nature of food poisoning outbreaks is changing and new threats emerge due to the modern way we make and eat food. The microbe <em>Campylobacter</em> used to be rare. Now it is commonplace in refrigerators and causes an estimated 100 deaths and around 300,000 serious infections a year, <a href="https://www.food.gov.uk/science/microbiology/campylobacterevidenceprogramme">costing the UK £900m and the US several billion</a>. Pork is another regular problem as shown by <a href="https://www.theguardian.com/environment/2016/oct/03/revealed-mrsa-variant-found-in-british-pork-at-asda-and-sainsburys">a recent MRSA outbreak</a> in the UK.</p>
<p>A <a href="http://www.consumerreports.org/cro/2012/05/how-safe-is-that-chicken/">2015 food safety survey</a> found that <em>Campylobacter</em> was present in 73% of the supermarket chickens tested and, of those, the majority were resistant to some antibiotics and many with high enough levels of microbes to cause infections. The meat <a href="https://www.food.gov.uk/sites/default/files/multimedia/pdfs/campyloconf.pdf">industry says</a> they can’t eradicate the problem and keep prices low. While we have a culture of cheap processed food at any price, the consumer and taxpayer take the risk – and <a href="http://tna.europarchive.org/20141204090942/http://www.food.gov.uk/news-updates/news/2011/4805/iid2">11m days a year off work </a> just in the UK is the result.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/140751/original/image-20161006-32702-1q1679z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/140751/original/image-20161006-32702-1q1679z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=411&fit=crop&dpr=1 600w, https://images.theconversation.com/files/140751/original/image-20161006-32702-1q1679z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=411&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/140751/original/image-20161006-32702-1q1679z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=411&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/140751/original/image-20161006-32702-1q1679z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=516&fit=crop&dpr=1 754w, https://images.theconversation.com/files/140751/original/image-20161006-32702-1q1679z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=516&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/140751/original/image-20161006-32702-1q1679z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=516&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Just let them.</span>
<span class="attribution"><span class="source">Manoonson Sonon</span></span>
</figcaption>
</figure>
<p>Educating parents and children about refrigerator hygiene is vital if we insist on eating cheap meat. Until the meat is cooked thoroughly it should be treated like a radioactive substance from the moment you touch the wrapper in the supermarket and ensuring surfaces, utensils and hands washed with soap, detergent and hot water. </p>
<p>Vegetables are much less of a problem. For the trendy modern semi-vegetarian family who knows where their vegetables come from, the only significant risk they run is a bit of grit while gaining millions of temporary soil microbes which may be beneficial. The only greens I would always avoid are sprouted foods (bean sprouts, watercress) used in salads which you shouldn’t trust. They are usually grown in a warm, moist environment where bacteria thrive. Sprouts contaminated with E.coli caused the worst outbreak in modern history <a href="http://edition.cnn.com/2011/WORLD/europe/06/05/europe.e.coli/">killing 51 Germans in 2011</a>. </p>
<p>If you’re healthy you don’t need to wash your hands after going on public transportation, chopping veg, gardening or a walk in the woods. But do be careful around meat, refrigerators, toilets and disease outbreaks. And if your kid drops something on your floor and you are sure it isn’t in a puddle of chicken blood – then the five second rule should still be fine. If it’s a fallen dummy sucking it yourself <a href="http://www.telegraph.co.uk/news/health/news/10875756/Mothers-should-suck-their-babies-dummies-scientists-say.html">has been shown</a> to reduce allergies. Playing with the dog and other animals and getting dirty outside in the garden or park should also be encouraged. </p>
<p>As we increasingly discover the benefits of increased exposure to microbes we urgently need more information and education so we can make informed decisions on the foods we buy, the antibiotics we ingest and the lifestyle choices we make to reverse our decline in diversity. All this has to be balanced against taking too many risks with modern intensively farmed foods which should now come with health warnings.</p><img src="https://counter.theconversation.com/content/66647/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tim Spector is director of the British Gut Project, co-founder of MapMyGut Ltd and receives grants on the microbiome from the MRC, CDRF and NIH. He is an SAB member of Optibiotix Ltd.
He is author of a book on gut microbes "The Diet Myth: the real science behind what we eat "- by W&N 2015 </span></em></p>Food poisoning or allergies – which to go for.Tim Spector, Professor of Genetic Epidemiology, King's College LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/572282016-04-26T09:27:04Z2016-04-26T09:27:04ZYour lungs are full of microorganisms … and that’s a good thing<figure><img src="https://images.theconversation.com/files/120063/original/image-20160425-22352-155prtx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The types of bugs that may be calling your lungs home</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-214336648/stock-photo-growth-of-pathogenic-bacteria-populations-populations-from-commercial-toilet-in-petri-dish.html?src=m1iaLRV6vRDo-nk7WcUnlw-1-34">www.shutterstock.com</a></span></figcaption></figure><p>When we’re born, our lungs are thought to be sterile. But from the moment we take our first breath, our pristine lungs are exposed to all the bugs that are in the air. It has become clear in the last 10 years that the lungs rapidly acquire a population of many different microorganisms (mostly bacteria and viruses) that colonise the lungs and remain with us for the rest of our lives. This population of bugs is called the lung microbiome.</p>
<p>We now know more about the lung microbiome thanks to genetics. In the past, identifying the types of bugs present in the lungs depended on being able to grow them in a laboratory, and for many types of bug this was difficult. The big change that happened recently is our ability to recognise both the different bug species, and their relative abundance, by using <a href="https://www.genome.gov/10001177/dna-sequencing-fact-sheet/">DNA sequencing</a>. This can be done either from a sample taken from the lungs or from sputum (the mucus we cough up when we have an infection).</p>
<h2>Is the lung microbiome a good or a bad thing?</h2>
<p>We all know that bacteria in the lungs can be harmful. When harmful bacteria multiply, they cause <a href="http://www.nhs.uk/conditions/pneumonia/Pages/Introduction.aspx">pneumonia</a> which, despite the existence of antibiotics, can still be deadly. However, it seems that the lung microbiome usually exists in a balanced state, such that harmful types of bugs do not increase in number sufficiently to cause pneumonia. In fact, it’s possible that the very presence of such a diverse range of bugs in the lungs is one of the reasons it’s quite difficult for harmful bugs to multiply and cause disease.</p>
<p>There are a number of reasons why the lung microbiome is important. It can alter when we have underlying chest diseases, especially those in which there are marked structural changes in the lungs. A good example is <a href="http://www.nhs.uk/conditions/Cystic-fibrosis/pages/introduction.aspx">cystic fibrosis</a>. In this disorder, a fault in a gene changes a protein that regulates the movement of salt in and out of cells. It results in sticky sputum and infections, which in turn can cause structural damage to the airways – a condition called <a href="http://www.nhs.uk/Conditions/Bronchiectasis/Pages/Introduction.aspx">bronchiectasis</a>. </p>
<p>This makes it easier for some kinds of bacteria – especially <em><a href="https://www.blf.org.uk/support-for-you/pseudomonas">Pseudomonas</a></em> – to grow in the lungs, and it becomes very difficult to get rid of these bacteria. The continuing inflammation in the lungs leads to more damage and the chest disease worsens. Treatment is therefore aimed at trying to eradicate these damaging bacteria, but it’s very difficult to eradicate infection once it has become established.</p>
<p>The difficulties of treating infection in patients with cystic fibrosis have been known for a long time. Recently, attention has been focused on trying to identify if changes in the lung microbiome are present in other more common chest diseases, <a href="http://www.ncbi.nlm.nih.gov/pubmed/27078029">such as asthma</a> or <a href="http://www.ncbi.nlm.nih.gov/pubmed/?term=PMID%3A+26917613">chronic obstructive pulmonary disease</a> (COPD). Recent work has suggested that the bugs grown from airways in patients with these conditions can be different from bugs grown in healthy people. This raises the intriguing possibility that the different bugs present may, in part, be responsible for either the development of these diseases, or for altering the severity of disease once it develops. </p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/119641/original/image-20160421-26976-1xeigbi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/119641/original/image-20160421-26976-1xeigbi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/119641/original/image-20160421-26976-1xeigbi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/119641/original/image-20160421-26976-1xeigbi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/119641/original/image-20160421-26976-1xeigbi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/119641/original/image-20160421-26976-1xeigbi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/119641/original/image-20160421-26976-1xeigbi.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">COPD symptoms include an ongoing cough that produces a lot of mucus.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-174190997/stock-photo-auscultation-elderly-person.html?src=gEZjH2gL5CnAiGy7z55jIQ-1-2">Image Point Fr</a></span>
</figcaption>
</figure>
<p>If it does prove to be the case that the different types of bugs in our lungs are in part responsible for development of chest disease, it follows that altering the lung microbiome might be a useful treatment. Directly altering the lung microbiome by administering “friendly” bacteria into the gut or lungs has mostly been <a href="http://www.ncbi.nlm.nih.gov/pubmed/?term=PMID%3A+26548605">tested in animals</a> to date. There are, however, examples of this approach working in other kinds of disease, particularly for conditions affecting the gut, for example for the <a href="http://www.ncbi.nlm.nih.gov/pubmed/?term=PMID%3A+25780308">treatment of irritable bowel syndrome</a>.</p>
<h2>Altering the lung microbiome</h2>
<p>I think the most important question about the lung microbiome is whether or not altering it could be helpful in treating or preventing chest disease. A good example is asthma. It’s well recognised that asthma seems to be more common in countries where early childhood exposure to infection is low. It has also been suggested that this increase in risk is due to lack of exposure to bugs in early life (an idea called the <a href="https://theconversation.com/infants-with-siblings-and-pets-less-likely-to-develop-allergies-9523">hygiene hypothesis</a>. </p>
<p>Some work has suggested that asthma risk could be reduced by encouraging early exposure to bugs, for example by spending more time in dirtier environments such as farms. Whether or not this approach works in the long term remains unclear, but if it does, it seems likely that changes in the lung microbiome may in part be responsible for the beneficial effects.</p><img src="https://counter.theconversation.com/content/57228/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span> I have research grants on asthma and COPD although none are related to work on the lung microbiome.</span></em></p>Understanding the bugs in our lungs could help treat certain diseases, including asthma.Ian Hall, Dean of the Faculty of Medicine and Health Sciences, University of NottinghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/505722016-01-13T10:59:03Z2016-01-13T10:59:03ZIf being too clean makes us sick, why isn’t getting dirty the solution?<figure><img src="https://images.theconversation.com/files/106318/original/image-20151216-30102-sybi4b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Wash up.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/foto_olio/19866673871/in/photolist-wgxTZR-7Kya2e-nQpUGf-8BSCUv-nQbxFv-7E14Qi-687mJZ-iCKfvF-7vb2gm-7SyJ5q-4wk3pb-51QRoS-aUGxrc-Qaekc-65jMSj-6LZJ1j-8F25oB-6cE82S-7EBBho-d3VwBm-d3Vxr5-4cY8DR-ggY9KN-pubsZs-52AUXy-frskit-Nydxd-NUawB-8eZ1HK-8xcfPC-6umFkA-99Bf6W-3mjV7u-8F7RfU-5v1xE9-3KFASh-AzrkYD-5BF2Vu-7RYRCk-nFcKVq-5PA2Lp-aisNKC-4D1msu-5mQxr4-mUY6M2-a1AVCk-qBd8cJ-8YifTS-WhXsQ-Reagm">Riccardo Meneghini/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>Today rates of allergic, autoimmune and other inflammatory diseases <a href="http://www.ncbi.nlm.nih.gov/pubmed/18087704">are rising dramatically in Western societies</a>. If that weren’t bad enough, we are beginning to understand that many psychiatric disorders, including depression, migraine headaches and anxiety disorders, <a href="http://dx.doi.org/10.4303/jem/235910">are associated with inflammation</a>. Perhaps the most startling observation is that our children are afflicted with the same inflammatory problems, contributing to the fact that <a href="http://dx.doi.org/10.1016/j.acap.2010.08.011">over 40 percent of US children</a> are on medications for some chronic condition. </p>
<p>And the cause, according to the “<a href="http://dx.doi.org/10.1136/bmj.g5267">hygiene hypothesis</a>,” is that being too clean causes a malformation of the immune system, leading to a wide range of inflammatory diseases. The original idea was that decreased infections in childhood due to hygiene led to a weak immune system, prone to become allergic and inflamed. </p>
<p>If the problem is that we are too clean, then, hypothetically, the issue can be easily resolved. We just need to get dirty, right? Wrong.</p>
<p>Getting dirty doesn’t help our immune system and generally makes inflammation worse. Much worse. That means there is something very wrong with the hygiene hypothesis. </p>
<h2>Biodiversity is the real issue</h2>
<p>What we actually have is a biodiversity problem. Our clean, indoor-centered lives and a Western diet rich in processed foods have depleted our biomes – the bacteria and worms that naturally live in our bodies, our guts in particular. These organisms play a role in the development and regulation of our immune systems, and scientists have identified the loss of biodiversity as being <a href="http://dx.doi.org/10.1111/cei.12269">central to the high rates of inflammatory disease</a> in the developed world.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/106322/original/image-20151216-30102-1eptlhn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/106322/original/image-20151216-30102-1eptlhn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/106322/original/image-20151216-30102-1eptlhn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/106322/original/image-20151216-30102-1eptlhn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/106322/original/image-20151216-30102-1eptlhn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/106322/original/image-20151216-30102-1eptlhn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/106322/original/image-20151216-30102-1eptlhn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Giving up soap won’t help your biome.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-145488505/stock-photo-bar-of-soap-with-suds.html?src=csl_recent_image-3">Bar of soap via www.shutterstock.com.</a></span>
</figcaption>
</figure>
<h2>The hygiene hypothesis was right…in its day</h2>
<p>An increase in inflammatory disorders, like allergies, was first observed about 150 years ago among the aristocracy in Europe, then reached the entire population of the industrialized world <a href="http://www.ncbi.nlm.nih.gov/pubmed/15833748?dopt=Abstract&holding=f1000,f1000m,isrctn">by the 1960s</a>, and seems only to have climbed steadily since then. </p>
<p>When trying to understand why <a href="http://link.springer.com/article/10.1007%2FBF02136147">inflammatory diseases increased in the late 1800s</a> and <a href="http://www.ncbi.nlm.nih.gov/pubmed/3129107">throughout the 20th century</a>, scientists put their finger on things such as toilets and water treatment facilities. In those days, having a toilet was “hygiene.” </p>
<p>But times change. After generations of living with toilets and water treatment facilities, some of the wildlife in our bodies has been <a href="http://www.yourwildlife.org/2015/05/ecological-medicine-can-parasitic-worms-cure-us-of-our-modern-pandemics/">driven to the point of extinction</a>. Our loss of contact with the soil due to indoor working environments has further depleted the wildlife of our bodies. And the typical Western diet doesn’t help either.</p>
<p>Even if you were to never use soap again for the rest of your life, you would not recover the wildlife your body is missing. Many of the lost organisms of our body don’t exist in North America in the wild, and others you simply won’t come across in your daily life.</p>
<p>On top of tremendous social difficulties imposed by a lack of soap, you’d likely increase your exposure to a lot of aggravating and even dangerous germs. The bacteria and viruses deposited on your shopping cart handle or the light switch at a hotel are generally <em>not</em> good. Those are often the <a href="http://dx.doi.org/10.1111/cei.12269">germs of modern society that cause infection and inflammation</a>. Your immune system would <a href="http://dx.doi.org/10.1111/j.1365-2222.2006.02463.x/full">remain inflamed</a>, and perhaps be even more agitated than before. </p>
<p>So what exactly are we missing? For practical purposes, it’s important to divide the wildlife of our bodies into two groups: microbes and more complex organisms such as worms. Microbes and worms affect our immune systems in different ways and both are important to be healthy. Biodiversity is the key.</p>
<h2>A healthy crop of microbes and a few good worms</h2>
<p>What would the gut biomes in our hunter-gatherer ancestors have looked like? A <a href="http://dx.doi.org/10.1038/nature11053">study</a> by Jeffrey Gordon at Washington University in St. Louis showed that people living in modern preindustrial societies had more diverse micriobiome compositions than people living in the United States today. Seventy bacterial species Gordon found in preindustrial people’s biomes were present in very different amounts from those found in the modern U.S. participants.</p>
<p>While each group may have been exposed to different kinds of bacteria in their day-to-day life, the primary reason for the difference in diversity was attributed to diet. The preindustrial folks ate a diet rich in corn and cassava, compared to a US diet rich in animal fat and protein. </p>
<p>And you might think that antibiotics are an issue, but they are usually less of a long-term problem for biodiversity. They can deplete bacteria in the gut microbiome, but the <a href="http://dx.doi.org/10.1038/nrmicro2536">dangerous and disease-inducing tailspin</a> is generally temporary. The microbiome usually recovers quite nicely, for the most part, <a href="http://dx.doi.org/10.1371/journal.pone.0009836">although some lingering effects can remain</a>.</p>
<p>The second group of organisms that we need are intestinal worms called helminths. These worms are called mutualists, because they benefit from us and we benefit from having them hanging around in our intestines. They used to <a href="http://theconversation.com/they-might-sound-gross-but-intestinal-worms-can-actually-be-good-for-you-49868">naturally live in our gut</a>. In fact, only 150 years ago most people in the West had <a href="http://dx.doi.org/10.1016/j.molbiopara.2009.04.008">intestinal worms that helped regulate immune function and prevent inflammatory disease</a>. The culprit here isn’t diet, but cleanliness and sanitation. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/106337/original/image-20151216-30088-mvrxv5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/106337/original/image-20151216-30088-mvrxv5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/106337/original/image-20151216-30088-mvrxv5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/106337/original/image-20151216-30088-mvrxv5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/106337/original/image-20151216-30088-mvrxv5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/106337/original/image-20151216-30088-mvrxv5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/106337/original/image-20151216-30088-mvrxv5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Eat some fiber.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/karimian/57925008">Ali Karimian/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>If getting dirty won’t help your biome, what can you do?</h2>
<p>When it comes to bacteria, a healthy diet is the critical ingredient. We can actually achieve a good mixture of gut bacteria very <a href="http://dx.doi.org/10.1038/nature12820">similar to that of our hunter-gatherer ancestors by adopting a good diet</a> high in fiber and low in processed foods. The right diet helps the good bacteria in your gut flourish, and might make it easier for new varieties of good bacteria to take root. </p>
<p>In addition, there are some products that might, in theory, support a more hunter-gatherer-like bacterial flora, by exposing us to the kind of bacteria we don’t encounter anymore, but they haven’t been tested in clinical trials. </p>
<p>Probiotics, generally formulations of bacteria such as <a href="http://www.ncbi.nlm.nih.gov/pubmed/10941602">bifidobacteria and lactobacilli that grow readily in milk</a>, are safe to use unless patients are <a href="http://dx.doi.org/10.1038/ajg.2008.68">severely ill</a>. They could help support biodiversity in our guts if we need <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2095085/">to take antibiotics</a>. </p>
<p>Worms are a bit more challenging. There are two schools of thought on how to help helminth-less guts: one is to figure out what makes good worms good for us, and develop a drug that can do the same thing. The other is just to have these good worms living in your intestines.</p>
<p>Personally, I don’t think we can <a href="http://evmedreview.com/reconstituting-the-depleted-biome-to-prevent-immune-disorders/">replicate complex biological relationships</a> using a drug. My view is that modern medicine will eventually <a href="http://dx.doi.org/10.1016/j.pt.2014.06.005">embrace the actual worm</a> or maybe complex single-celled organisms called protozoans that work the same way, but research in this field is still in the early stages of development. </p>
<p>In the meantime, some intrepid people are going straight for the worm. As in actually acquiring worms in their gut. The challenge for these adventurers is to find a worm that has more benefits than disadvantages.</p>
<p>For instance, the same species of worm can have different effects in different people. The human hookworm, for instance, is commercially available and easily cultured at home. It has been found to treat <a href="http://dx.doi.org/10.4303/jem/235910">multiple sclerosis and severe airway hypersensitivity</a> but can also cause severe gastrointestinal distress in many patients.</p>
<p>For now, most individuals interested in immune health will focus on those factors that are risk-free, like <a href="http://dx.doi.org/10.4303/jem/235885">avoiding chronic psychological stress</a>, eating well and exercising, and watching out for <a href="http://www.ncbi.nlm.nih.gov/pubmed/17634462">vitamin D deficiency</a>. These factors, all within our control, are important for avoiding a wide range of inflammation-related diseases, including allergy, autoimmunity, depression and cancer.</p><img src="https://counter.theconversation.com/content/50572/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>William Parker does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Being too clean isn’t what’s making us sick. It’s the loss of biodiversity in the bacteria and organisms that live in our bodies and work with the immune system.William Parker, Associate Professor of Surgery, Duke UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/403182015-10-07T19:24:44Z2015-10-07T19:24:44ZWhat are allergies and why are we getting more of them?<figure><img src="https://images.theconversation.com/files/95161/original/image-20150917-7521-3ppdou.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Allergies are becoming more frequent in the western world. </span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/al-stan/3475946574/">Al Fed/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>Allergies are reactions caused by the immune system as it responds to environmental substances that are usually harmless to most people. They may occur in response to a range of different material (called allergens), such as food, pollen, dust mites, animals, insect stings, or medicines.</p>
<p>An allergy can <a href="http://www.allergy.org.au">affect different parts of the body</a>. Allergic rhinitis, or hay fever, for instance, affects the nose and eyes, while eczema affects the skin. Food allergies affect the gut, skin, airways, lungs, and sometimes the entire body through the blood vessels. </p>
<p>Other conditions such as asthma, which affects the lungs, and eosinophilic oesophagitis, which affects the tube from the throat to the stomach, are closely related to allergy. But they have slightly different underlying causes. </p>
<h2>A range of reactions</h2>
<p>While most reactions are only mild to moderate in severity (and can be treated with antihistamines), some can be life-threatening and require emergency medical treatment. The most severe, systemic allergic reactions are known as anaphylaxis. People with known severe allergies should have an <a href="http://www.allergy.org.au">emergency management plan</a> that includes an adrenaline auto-injector for emergency use. </p>
<p>We can confirm whether someone has an allergy by doing a skin-prick testing or a blood test that checks whether their immune system has produced antibodies to an allergen. If the immune system has developed antibodies, it will remember the allergen as a potential threat and is likely to mount a strong immune response on subsequent exposure. </p>
<p>The likelihood of someone having an allergic reaction from future exposures to the allergen is determined by taking their clinical history and these test results into account. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/95141/original/image-20150917-12695-2a4xns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/95141/original/image-20150917-12695-2a4xns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=265&fit=crop&dpr=1 600w, https://images.theconversation.com/files/95141/original/image-20150917-12695-2a4xns.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=265&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/95141/original/image-20150917-12695-2a4xns.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=265&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/95141/original/image-20150917-12695-2a4xns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=333&fit=crop&dpr=1 754w, https://images.theconversation.com/files/95141/original/image-20150917-12695-2a4xns.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=333&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/95141/original/image-20150917-12695-2a4xns.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=333&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">Allergic rhinitis, or hay fever, affects the nose and eyes.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/14353437@N06/4515249683/">parrchristy/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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</figure>
<p>In the case of food allergy, if the probability of an allergic reaction is low, people are given a food challenge. This is when increasing amounts of the offending food are administered while the person is closely observed for any signs of an allergic reaction. Of course, it can result in a reaction.</p>
<p>Allergies are becoming more frequent in Australia and the rest of the western world. <a href="http://www.allergy.org.au/">One in three people in Australia</a> will develop allergies at some time in their life. One in 20 will develop a food allergy and one in 100 will have a life-threatening allergic reaction known as anaphylaxis .</p>
<p>Hospital admissions for anaphylaxis <a href="http://www.ncbi.nlm.nih.gov/pubmed/26187235">doubled in the ten years</a> from 1994 to 2004, and were five times higher in children under five years old over the same period. This suggests the development of allergy in early life is increasing at a faster rate than in adults.</p>
<p>Children are <a href="http://www.abc.net.au/news/2015-07-15/number-of-children-hospitalised-with-food-allergies-on-the-rise/6619752">more likely to develop allergies</a> to eggs, dairy products or peanuts, while adults are more likely to develop an allergy to seafood. </p>
<h2>Possible reasons why</h2>
<p>The reasons for the rising number of allergies are not fully understood, but here are six theories.</p>
<p>1) Decreased exposure to infections or microbes – or both – in early life could lead to an increased risk of allergy. This is commonly referred to as the hygiene hypothesis, <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1838109/">first suggested in 1989</a>. <a href="http://www.ncbi.nlm.nih.gov/pubmed/21060319">Research showing</a> children who have close contact with pets or livestock and those who come from larger families are less likely to develop allergies have indirectly supported the hygiene hypothesis.</p>
<p>2) Delayed introduction of allergenic foods, such as eggs and nuts, until later in childhood could also have an impact. This is one of the most recent theories resulting from the <a href="http://www.nejm.org/doi/full/10.1056/NEJMoa1414850">LEAP study</a>, published in 2015. This randomised trial for early life peanut consumption in a population at increased risk of developing peanut allergies demonstrated that exposure to the nut early in life is protective against developing the allergy.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/95162/original/image-20150917-7517-3j4zx9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/95162/original/image-20150917-7517-3j4zx9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=385&fit=crop&dpr=1 600w, https://images.theconversation.com/files/95162/original/image-20150917-7517-3j4zx9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=385&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/95162/original/image-20150917-7517-3j4zx9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=385&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/95162/original/image-20150917-7517-3j4zx9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=483&fit=crop&dpr=1 754w, https://images.theconversation.com/files/95162/original/image-20150917-7517-3j4zx9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=483&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/95162/original/image-20150917-7517-3j4zx9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=483&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A child with a nut allergy only has a 20% chance of the allergy resolving by the time she reaches adulthood.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/aoifemac/8424630783/">Aoife Mac/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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</figure>
<p>3) Different methods of preparing foods can <a href="http://www.ncbi.nlm.nih.gov/pubmed/19000582">impact the degree</a> to which they invoke an allergic response; roasting peanuts, for instance, greatly increases allergenicity while boiling reduces it. This may in part explain difference in incidence of in peanut allergy between certain countries.</p>
<p>4) Vitamin D deficiency may increase the risk to develop allergies. Several studies show that the further away you live from the equator (hence your lower level of sunlight exposure, which is needed to make Vitamin D) – or <a href="http://www.abc.net.au/health/features/stories/2013/03/07/3710140.htm">low vitamin D blood levels increase your risk</a> of developing allergies. But the value of vitamin D treatment for preventing allergies has yet to be demonstrated. </p>
<p>5) Allergies may develop after exposure to allergens, such as dairy products or nut oils in skin moisturisers, particularly on inflamed sites, such as eczema.</p>
<p>6) Altered gut bacterial species due to low-fibre diets and widespread antibiotic usage may alter the body’s immune function and create an allergy.</p>
<p>Whether your allergy improves over time often depends on the type of allergy you have. A child with eczema, for instance, will often find her eczema improves by the time she’s a teenager. But some people will have eczema even into their adult years. In contrast, a child with peanut allergy only has a 20% chance of the allergy resolving by the time she reaches adulthood.</p>
<p>While we have treatments for the symptoms of allergy, we do not yet have a cure or the ability to prevent them from developing in the first place. We also don’t have a good test for predicting food allergy, unless we feed the person the suspected food allergen. For now, the best you can do is to manage your allergy.</p><img src="https://counter.theconversation.com/content/40318/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Adam Collison receives funding from the NHMRC, Hunter Children's Research Foundation and the Thrasher Research Fund. He is an inventor on a provisional patent that describes a marker for peanut allergy.</span></em></p><p class="fine-print"><em><span>Joerg Mattes receives/received funding from the National Health&Medical Research Council, the Hunter Medical Research Institute, the Hunter Children's Research Foundation, Asthma Australia, Rebecca L. Cooper Medical Research Foundation. He is a listed inventor on a patent describing a peanut anaphylaxis blood biomarker.</span></em></p><p class="fine-print"><em><span>Rani Bhatia receives funding from the Hunter Children's Research Foundation. She is an inventor on a provisional patent that describes a marker for peanut allergy.</span></em></p><p class="fine-print"><em><span>Elizabeth Percival 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>Allergies are reactions caused by the immune system as it responds to environmental substances that are usually harmless. But we don’t yet have a cure or the ability to prevent them from developing.Adam Collison, Post Doctoral researcher - Experimental and Translational Respiratory Medicine Research Group, University of NewcastleElizabeth Percival, Staff Specialist General Paediatrician at John Hunter Children's Hospital, Newcastle, Australia. Conjoint Lecturer & PhD student, University of NewcastleJoerg Mattes, Professor&Chair of Paediatrics | HMRI, University of Newcastle, Australia | Senior Staff Specialist Paediatric Respiratory&Sleep Medicine | John Hunter Children's Hospital, Australia, University of NewcastleRani Bhatia, Senior Staff Specialist in Paediatric Allergy and Immunology at John Hunter Children's Hospital Newcastle NSW Conjoint Lecturer in Paediatrics, University of NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/428552015-06-04T15:49:38Z2015-06-04T15:49:38ZFour myths about allergies you thought were true – but aren’t<figure><img src="https://images.theconversation.com/files/83967/original/image-20150604-3393-ipumqa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">I can't believe it isn't true.</span> <span class="attribution"><span class="source">Hayfever by Shutterstock</span></span></figcaption></figure><p>Allergies are on the rise across the developed world and hay fever and eczema have trebled <a href="http://thorax.bmj.com/content/62/1/91.short">in the last 30 years</a>. Yet allergies are an area of much confusion and concern. Although one study found 38% of people think they have a food allergy, <a href="http://www.sciencedirect.com/science/article/pii/S0091674907009918">in fact only 1-5% do</a>, and allergists commonly report spending most of their consultations refuting firmly held beliefs that have no scientific foundation.</p>
<p>Theories about allergy – some from medical research and some from lifestyle “gurus” – have led to conflicting information, making it hard to know what to believe. Because of this, <a href="http://www.senseaboutscience.org/">Sense About Science</a> worked with me and a number of allergists, immunologists, respiratory scientists and pharmacists to produce <a href="http://www.senseaboutscience.org/pages/making-sense-of-allergies.html">Making Sense of Allergies</a>, a guide tackling the many myths and misconceptions about allergies. One common myth – something that I work on – is the link between allergies and exposure to microbes. </p>
<p>So here is a hygiene and allergy reality fact check:</p>
<h2>Do fewer childhood infections mean more allergies?</h2>
<p><strong>No.</strong> Although a <a href="http://www.ifh-homehygiene.org/best-practice-review/hygiene-hypothesis-and-its-implications-home-hygiene-lifestyle-and-public">link between allergies and microbes</a> is largely accepted, the idea that more infections during childhood reduces the chance of developing allergies is now discounted. This idea came from <a href="http://www.nhs.uk/livewell/homehygiene/pages/are-we-too-clean-for-our-own-good.aspx">the hygiene hypothesis</a>, proposed in 1989, which theorised that the 20th century’s increase in allergies was due to lower rates of infection in early childhood. This hypothesis was based on observations that larger family size protected against hay fever, while smaller families were thought to provide insufficient infection exposure because of less person-to-person infection.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/83973/original/image-20150604-3407-1557u8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/83973/original/image-20150604-3407-1557u8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/83973/original/image-20150604-3407-1557u8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/83973/original/image-20150604-3407-1557u8m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/83973/original/image-20150604-3407-1557u8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/83973/original/image-20150604-3407-1557u8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/83973/original/image-20150604-3407-1557u8m.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">Infection not protection.</span>
<span class="attribution"><span class="source">Ill by Shutterstock</span></span>
</figcaption>
</figure>
<p>Exposure to a normal range of microbes during the first months after birth is critical to developing the immune system, but there is no evidence that “regular” infections are important to boost general infection immunity or prevent allergies.</p>
<h2>Are allergies up because of modern obsessions with cleanliness?</h2>
<p><strong>No.</strong> Our microbiomes, the population of microbes that live in and on our bodies, have altered from previous generations. This is not because of cleanliness, but because we interact with less diverse microbial environments than those of our largely rural ancestors. The idea that excessive cleaning has created “sterile” homes is implausible: microbes are rapidly replaced by organisms shed from us, our pets, raw foods and dust.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/83972/original/image-20150604-3387-1rystnt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/83972/original/image-20150604-3387-1rystnt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/83972/original/image-20150604-3387-1rystnt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/83972/original/image-20150604-3387-1rystnt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/83972/original/image-20150604-3387-1rystnt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/83972/original/image-20150604-3387-1rystnt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/83972/original/image-20150604-3387-1rystnt.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">
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<span class="caption">Not such a bad thing.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-146517557/stock-photo-hygiene-cleaning-hands-washing-hands.html?src=RNcCUOu47fMK8IiagBocxg-1-14">Washing by Shutterstock</a></span>
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</figure>
<p>This understanding has come from the <a href="http://onlinelibrary.wiley.com/doi/10.1111/cei.12269/full">“old friends” mechanism</a>, a refinement to the hygiene hypothesis that offers a more plausible explanation for the link between microbial exposure and allergies. It proposes that exposure to the diverse range of largely non-harmful microbes or parasites that inhabit our world are important for building a diverse microbiome that is vital for sustaining a well regulated immune system that doesn’t overreact to allergens like pollen. These “old friends” have co-evolved with humans over millions of years. By contrast most infectious diseases only emerged over the last 10,000 years as we came to live in urban communities.</p>
<p>Old friend microbes are still there, <a href="https://theconversation.com/parasites-harder-to-swallow-but-we-already-take-probiotics-18574">but we have lost contact</a> with them due to lifestyle and public health changes over the past two centuries. Improved water quality, sanitation and urban cleanliness have massively reduced infectious disease, but inadvertently deprived us of exposure to these microbes. Changes in microbial content of food, less breastfeeding, more caesarean sections, urban rather than rural living and increased antibiotic use have also reduced early life old friends interaction.</p>
<h2>Will relaxing hygiene reverse the trend in allergies?</h2>
<p><strong>No.</strong> We now know that relaxing hygiene will not reunite us with our old friends, but carries the risk of increased exposure to other microbes that can cause old and new diseases. Because it was originally called the “hygiene” hypothesis, and because the terms hygiene and cleanliness are used interchangeably, people often assume that “being less clean” implies being less particular about hygiene.</p>
<p>At the same time that allergies have increased, the threats of global pandemics and <a href="https://theconversation.com/uk/topics/antibiotic-resistance">antibiotic resistance</a> have increased, and hygiene is key to containing these threats. Protecting against infection is not about how clean our homes look or how often we shower, it’s what we do to stop germs spreading. </p>
<p>By using “targeted” hygiene practices such as hand washing, food safety and toilet hygiene, while encouraging everyday interactions with our microbial world we maximise protection against infection, while maintaining exposure to old friends.</p>
<h2>Are synthetic chemicals linked to rising allergies?</h2>
<p><strong>No.</strong> Excessive use of cleaning and personal care products and antibacterials is sometimes said to be linked to allergies because it deprives us of microbial exposure. Antibacterial products are perceived to exacerbate this. However, because <a href="http://www.ifh-homehygiene.org/best-practice-review/hygiene-hypothesis-and-its-implications-home-hygiene-lifestyle-and-public">evidence suggests</a> that general day-to-day home cleaning has no impact on microbial levels, it is unlikely to impact on our human microbiome. By contrast targeted disinfectant use, for example while preparing food, <a href="http://www.ncbi.nlm.nih.gov/pubmed/10664978">can reduce infection risks</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/83970/original/image-20150604-3403-1uilya2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/83970/original/image-20150604-3403-1uilya2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/83970/original/image-20150604-3403-1uilya2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/83970/original/image-20150604-3403-1uilya2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/83970/original/image-20150604-3403-1uilya2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/83970/original/image-20150604-3403-1uilya2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/83970/original/image-20150604-3403-1uilya2.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">Counting the number.</span>
<span class="attribution"><span class="source">Test by Shutterstock</span></span>
</figcaption>
</figure>
<p>Many people believe that “man-made” chemicals are more likely to cause allergic reactions, leading to many synthetic substances in products being replaced by “natural alternatives”. However, the most common allergic reactions are to naturally occurring allergens, in foods such as eggs, milk and nuts, in common garden plants such as primroses and chrysanthemums, and things in the environment such as pollen, dust mites and pet dander. Some natural replacements for synthetic substances could actually increase the risk of allergic reactions.</p><img src="https://counter.theconversation.com/content/42855/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sally Bloomfield is Chairman of the International Scientific Forum on Home Hygiene. This is a not for profit Charitable Trust, which is funded by an educational grant and project funding from the private and public sector</span></em></p>Most people who report allergies don’t actually have them – and there are other things you may find surprising.Sally Bloomfield, Honorary Professor, London School of Hygiene & Tropical MedicineLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/95232012-09-19T04:27:21Z2012-09-19T04:27:21ZInfants with siblings and pets less likely to develop allergies<figure><img src="https://images.theconversation.com/files/15534/original/7q2mq8pb-1347852208.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Early exposure to siblings and dogs may help to train the developing immune system.</span> <span class="attribution"><span class="source">Flickr/henry...</span></span></figcaption></figure><p>Having older siblings and a dog that lives in the home could reduce the likelihood of infants developing egg allergies, according to a new study published in the latest edition of the journal <a href="http://onlinelibrary.wiley.com/doi/10.1111/all.12015/abstract">Allergy</a>. </p>
<p>Food allergy, along with its most concerning manifestation – <a href="http://www.allergy.org.au/patients/about-allergy/anaphylaxis">anaphylaxis</a> (a life-threatening allergic reaction) – is an <a href="http://www.allergy.org.au/patients/food-allergy/food-allergy">increasingly common problem</a> among children in many industrialised countries including Australia. </p>
<p>Egg allergy is the most common food allergy in infants and young children, affecting around 8% of 12-month-old infants <a href="http://www.allergycapital.com.au/allergycapital/Allergies_in_Australia.html">in Melbourne</a>. Although egg allergy itself often resolves, it’s a potential early marker for the later development of other allergic conditions such as asthma and allergic rhinitis (hay fever).</p>
<h2>Testing the environment</h2>
<p>In this study of over 5,000 infants, my colleagues and I investigated the role of a wide range of environmental and demographic factors have on the development of egg allergy. This included the number of older siblings, contact with other children during childcare, exposure to pets, caesarean delivery, infant diet, parents’ country of birth, family history of allergy and the use of antibiotics in infancy. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/15537/original/j3trz784-1347853473.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/15537/original/j3trz784-1347853473.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/15537/original/j3trz784-1347853473.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/15537/original/j3trz784-1347853473.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/15537/original/j3trz784-1347853473.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/15537/original/j3trz784-1347853473.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/15537/original/j3trz784-1347853473.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">
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<span class="caption"></span>
<span class="attribution"><span class="source">rubygirl jewelry</span></span>
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<p>We recruited infants at 12 months of age from council-led immunisation programs across Melbourne. Every child underwent a skin prick test – a screening test to identify which infants were at risk of food allergy. About half of those testing positive are expected to be truly allergic. </p>
<p>Any child with a positive screening test then underwent an oral food challenge. This involves giving small amounts of the food that caused a reaction on the skin prick test in increasing doses in a medical setting and monitoring for any reactions. This is the gold standard for diagnosis of food allergy, particularly in those who have never eaten the food in question.</p>
<p>We found that infants with siblings and infants with a pet dog inside the home were less likely to be allergic to egg at one year of age. Of the infants with no siblings, 10.8% were allergic to egg, however as the number of siblings increased, the incidence of egg allergy decreased; the rate of egg allergies in infants who had three or more siblings was almost three-fold lower. </p>
<p>We also found a link to dog ownership, with infants in families with no dogs almost twice as likely to have an egg allergy than those who had a dog who was allowed inside the house. This protective effect of dog exposure was present even among those with no family history of allergic disease, suggesting the finding couldn’t be explained by allergic families choosing to avoid dogs.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/15544/original/jmxckh4n-1347855967.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/15544/original/jmxckh4n-1347855967.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/15544/original/jmxckh4n-1347855967.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/15544/original/jmxckh4n-1347855967.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/15544/original/jmxckh4n-1347855967.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/15544/original/jmxckh4n-1347855967.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/15544/original/jmxckh4n-1347855967.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">Having a dog in the house seems to protect infants against egg allergies.</span>
<span class="attribution"><span class="source">TheGiantVermin</span></span>
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</figure>
<h2>The hygiene hypothesis</h2>
<p>Our findings provide support for the hygiene hypothesis in the development of food allergy. The hygiene hypothesis has previously been implicated in other allergic diseases, particularly allergic rhinitis. However, few studies have investigated whether early life exposures to siblings and pets may play a role in the development of food allergy. </p>
<p>Broadly, the hygiene hypothesis is an evolving theory which states that the immune system needs to be exposed to appropriate stimulation during development so that it is “trained” to attack things that might cause us harm (such as bacterial or viral infections) while ignoring harmless things such as foods. </p>
<p>This stimulation could come from infections (by bacteria, viruses or parasites such as worms) or from harmless bacteria found in our environment. </p>
<p>So where do siblings and pets come in to this story? </p>
<p><a href="http://pediatrics.aappublications.org/content/108/4/943.abstract">Studies have shown</a> that children who have siblings have more infections early in life, which might help to train the developing immune system. Having a pet dog may act in a similar way to prevent allergy. Environments with pets tend to have more <a href="http://www.wisegeek.com/what-are-endotoxins.htm">endotoxins</a> (toxins which are found in some bacteria), which are very effective at stimulating the immune system. </p>
<p>Interestingly, although we know that childcare also increases exposure to infections, this did not seem to protect against the development of food allergy. This might be because infants generally did not attend childcare in the first few months of life. Perhaps only exposures that take place very early on in life are protective. </p>
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<img alt="" src="https://images.theconversation.com/files/15545/original/hdtyyksr-1347856086.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/15545/original/hdtyyksr-1347856086.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/15545/original/hdtyyksr-1347856086.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/15545/original/hdtyyksr-1347856086.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/15545/original/hdtyyksr-1347856086.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/15545/original/hdtyyksr-1347856086.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/15545/original/hdtyyksr-1347856086.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">
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<span class="caption"></span>
<span class="attribution"><span class="source">hoyasmeg</span></span>
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<p>So what would we advise parents to do to prevent food allergy? </p>
<p>Before we can answer that, there is still more work to be done. In particular, we need to identify which exposures are important in immune development. </p>
<p>Improved hygiene overall is a good thing – cleaner food and water supplies, for example, lead to a reduction in serious diseases. But ideally, we would like to identify some exposures that could prevent allergies without putting children at risk of infectious illnesses. </p>
<p>We have previously shown that later introduction of egg is strongly associated with risk of egg allergy. Combined with this knowledge, our new findings add to a growing body of evidence to identify possible causes of allergies.</p>
<p><em>The study was led by Professor Katrina Allen and a team of investigators from the Murdoch Childrens Research Institute and the University of Melbourne.</em></p><img src="https://counter.theconversation.com/content/9523/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>This study was supported by funding from the National Health & Medical Research Council (NHMRC) of Australia, Ilhan Food Allergy Foundation, AnaphylaxiStop, the Charles and Sylvia Viertel Medical Research Foundation and the Victorian Government's Operational Infrastructure Support Program. </span></em></p>Having older siblings and a dog that lives in the home could reduce the likelihood of infants developing egg allergies, according to a new study published in the latest edition of the journal Allergy…Jennifer Koplin, Postdoctoral Research Fellow, Population Health, Genes and Environment, Murdoch Children's Research InstituteLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/49282012-05-06T20:49:02Z2012-05-06T20:49:02ZEverything you need to know about coeliac disease (and whether you really have it)<figure><img src="https://images.theconversation.com/files/10100/original/t33f2bp8-1335761395.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Thinking of jumping on the gluten-free bandwagon? Better think again.</span> <span class="attribution"><span class="source">GlutenFreeChops/Flickr</span></span></figcaption></figure><p>The <a href="http://history-world.org/neolithic.htm">Neolithic Revolution</a> introduced a whole range of new foods and proteins into the human digestive tract. But this phenomenal change created the perfect conditions for the rise of coeliac disease. </p>
<p>While most proteins were readily consumed, some people’s immune systems struggled to tolerate others. Wheat was the first cereal to be widely domesticated, and in the case of the gluten protein from wheat, the result of this struggle was coeliac disease. </p>
<p>When people with coeliac disease consume gluten, an abnormal immune reaction occurs causing inflammation and damage to the small bowel lining. This impairs absorption of nutrients and can lead to a wide range of symptoms and medical complications.</p>
<h2>Ancient condition, 20th century treatment</h2>
<p>The second century Greek physician Arateus is credited with coining the term coeliac disease, or “koiliakos”, after the Greek word koelia (abdomen), to describe patients suffering typical symptoms of diarrhoea, weight loss and anaemia. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/10092/original/nw4mrfhq-1335759356.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/10092/original/nw4mrfhq-1335759356.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/10092/original/nw4mrfhq-1335759356.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/10092/original/nw4mrfhq-1335759356.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/10092/original/nw4mrfhq-1335759356.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/10092/original/nw4mrfhq-1335759356.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/10092/original/nw4mrfhq-1335759356.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">
<figcaption>
<span class="caption">Wheat was finally identified as the culprit of the reoccurring health problems.</span>
<span class="attribution"><span class="source">Joana Hard</span></span>
</figcaption>
</figure>
<p>Reports from the 19th and 20th century reveal considerable suffering and mortality associated with coeliac disease, particularly in infants. An effective treatment didn’t arise until the middle of the 20th century, when gluten was identified as the culprit. </p>
<p>The discovery was fortuitous – a wartime bread shortage led Dutch paediatrician Willem Dicke to observe improved health in children with coeliac disease, and note their relapse shortly after food drops of bread returned wheat back into their diet. </p>
<p>The work of Australian physician Charlotte Anderson established it was the gluten component of wheat (and also rye, barley and oats) that caused coeliac disease. It was the 1950s and the age of treatment with a gluten-free diet had begun.</p>
<h2>Prevalence and the reasons why</h2>
<p>Far from being a medical rarity, coeliac disease is very common today, affecting more than one in 100 Australians. And in the last half century, it has become approximately <a href="http://www.ncbi.nlm.nih.gov/pubmed/17944736">twice as common every two decades</a>, similar to the rise in other immune diseases, such as type 1 diabetes. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/10093/original/qqhzzm5n-1335759870.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/10093/original/qqhzzm5n-1335759870.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/10093/original/qqhzzm5n-1335759870.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/10093/original/qqhzzm5n-1335759870.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/10093/original/qqhzzm5n-1335759870.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/10093/original/qqhzzm5n-1335759870.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/10093/original/qqhzzm5n-1335759870.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">
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<span class="caption">The increased prevalence of the disease may be due to hyper-conscious hygiene practices.</span>
<span class="attribution"><span class="source">sydeen/Flickr</span></span>
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</figure>
<p>Why the prevalence is increasing remains unknown, but a variety of environmental factors and the “<a href="https://theconversation.com/how-clean-is-too-clean-trust-your-gut-instincts-855">hygiene hypothesis</a>” have been proposed. </p>
<p>Today, people are typically diagnosed in adulthood and are mostly female. Alarmingly, <a href="http://www.ncbi.nlm.nih.gov/pubmed/21426277">80% of Australians with coeliac disease remain undiagnosed</a>. This is because symptoms are wide-ranging and largely non-specific. And coeliac disease still remains “off the radar” for many doctors.</p>
<h2>Many symptoms but simple diagnosis</h2>
<p>In people with coeliac disease, gluten causes widespread inflammation not limited to the bowel. Patients are commonly troubled by gut upset (such as bloating, abdominal pain, diarrhoea and/or constipation), lethargy, anaemia, and nutrient deficiencies, such as low iron. They can also suffer loss of fertility, migraine headaches, abnormal liver function, arthritis and autoimmune diseases, such as type 1 diabetes and autoimmune thyroid disease. </p>
<p>Bones are more likely to be thinned out (osteoporosis) and patients can develop certain cancers, such as lymphoma. The good news is that early diagnosis and treatment can greatly reduce the chances of these complications.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/10094/original/w9jpcx6b-1335760316.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/10094/original/w9jpcx6b-1335760316.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=425&fit=crop&dpr=1 600w, https://images.theconversation.com/files/10094/original/w9jpcx6b-1335760316.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=425&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/10094/original/w9jpcx6b-1335760316.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=425&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/10094/original/w9jpcx6b-1335760316.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/10094/original/w9jpcx6b-1335760316.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/10094/original/w9jpcx6b-1335760316.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A blood test is a simple way to indicate whether you may have coeliac disease.</span>
<span class="attribution"><span class="source">Healthcare Experts/Flickr</span></span>
</figcaption>
</figure>
<p>A simple blood test is used to screen for coeliac disease, although making a definite diagnosis requires demonstrating the characteristic small bowel changes of flattened and inflamed lining (“villous atrophy”) under the microscope. Small bowel samples are readily obtained by gastroscopy, a ten-minute procedure performed under sedation that introduces a flexible instrument via the mouth into the small bowel to allow samples to be taken. </p>
<p>It’s vital that a gluten-free diet isn’t started before testing for coeliac disease, as this can cause false negative results.</p>
<h2>Genes and the environment</h2>
<p>Coeliac disease shares certain predisposing genes with autoimmune diseases, such as type 1 diabetes (which explains why these conditions often occur together). These genes control how the immune system “recognises” and responds to foreign proteins and are fundamental for disease to develop. </p>
<p>But genes alone are not enough to cause coeliac disease and environmental factors are thought to play an important role in “triggering” disease in those with genetic susceptibility. Some factors appear to increase coeliac disease risk (such as <a href="http://www.ncbi.nlm.nih.gov/pubmed/17032199">rotavirus infection</a> in infancy) while some may reduce the risk. <a href="http://www.ncbi.nlm.nih.gov/pubmed/11976167">Breastfeeding at the time gluten is introduced</a> to an infant, for instance, may protect against developing disease. </p>
<h2>The challenge of gluten-free diets</h2>
<p>Excluding all dietary sources of gluten from wheat, rye, barley and oats allows the small bowel damage to heal and symptoms to resolve – but it’s far from easy. Wheat flour, the most common and significant source of gluten, is found in many foods, such as bread, breakfast cereals, cakes, biscuits, pasta, pastries and pizzas. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/10096/original/r9h3cp6d-1335760638.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/10096/original/r9h3cp6d-1335760638.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/10096/original/r9h3cp6d-1335760638.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/10096/original/r9h3cp6d-1335760638.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/10096/original/r9h3cp6d-1335760638.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/10096/original/r9h3cp6d-1335760638.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/10096/original/r9h3cp6d-1335760638.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">
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<span class="caption">People with coeliac disease have to learn how to pass up the pastries.</span>
<span class="attribution"><span class="source">pastryfusion/Flickr</span></span>
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<p>There are also “hidden” sources of gluten found in sauces and processed foods and less obvious items, such as malted foods and beer. While gluten-free alternatives are increasingly available, they’re much more expensive and generally much less palatable – anyone who has ever tried gluten free bread will know how dense and crumbly it is! </p>
<p>Compounding its complexity, cost and poor palatability, the gluten-free diet needs to be very strict to work - even <a href="http://www.ncbi.nlm.nih.gov/pubmed/17209192">small amounts of gluten</a> (about 50 milligrams – less than 1/100th of a slice of bread) can cause bowel damage. </p>
<p>That’s why patients need to be obsessive about excluding gluten – for people with coeliac disease the gluten free diet is not a fad but a serious medical treatment.</p>
<h2>Is gluten free for everyone?</h2>
<p>It’s hard to miss the ever-expanding sections of supermarkets dedicated to selling gluten-free food and many restaurant menus list gluten-free options. The gluten-free food industry is booming, with a global market projected to well exceed US$4 billion over the next three years. </p>
<p>Interestingly, a recent market survey commissioned by <a href="http://www.coeliac.org.au/">Coeliac Australia</a> indicates that approximately 10% of Australians are currently following a strict or significantly reduced gluten diet. This is ten times greater than the total number of Australians thought to have coeliac disease.</p>
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<img alt="" src="https://images.theconversation.com/files/10099/original/qh39m5s9-1335761035.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/10099/original/qh39m5s9-1335761035.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/10099/original/qh39m5s9-1335761035.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/10099/original/qh39m5s9-1335761035.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/10099/original/qh39m5s9-1335761035.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/10099/original/qh39m5s9-1335761035.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/10099/original/qh39m5s9-1335761035.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&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">A gluten-free diet isn’t all that tasty, and not necessarily the healthiest option.</span>
<span class="attribution"><span class="source">simply..gluten-free/Flickr</span></span>
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</figure>
<p>It’s likely that alternative health practitioners, disease advocacy groups, proliferating internet blogs and forums, and the gluten-free food industry are directly or indirectly fuelling the mounting public perception that a gluten-free diet is intrinsically “healthy” or suitable to treat a variety of symptoms and illnesses. </p>
<p>But medical evidence to support undertaking a strict gluten-free diet outside of coeliac disease is <a href="http://www.ncbi.nlm.nih.gov/pubmed/22237879">minimal</a>. If people do choose to follow a gluten free diet, it’s medically important that coeliac disease is excluded first so that testing isn’t compromised - a missed diagnosis of coeliac disease can be disastrous for long-term health. </p>
<p>While many people feel their symptoms might improve on a gluten-free diet, this doesn’t necessarily mean they have coeliac disease. Nor does it mean a gluten-free diet is the most appropriate treatment for them. </p>
<p>Many cases of perceived wheat or gluten intolerance reported by patients is not due to gluten itself but intolerance to the wheat’s carbohydrate component (fructans). For some, a diet reducing fructans and other fermentable carbohydrates, a <a href="http://www.ncbi.nlm.nih.gov/pubmed/20136989">low FODMAP (fermentable oligo-, di-, mono-saccharides and polyols) diet</a> can be a more effective and appropriate treatment than going gluten free. </p>
<h2>Awareness, diagnosis and management</h2>
<p>Inadequate and delayed diagnosis of coeliac disease remains a major problem in our community so improving awareness and testing is a major goal to reduce the burden of this disease. </p>
<p>Excitingly, there’s been significant progress in understanding the <a href="http://www.ncbi.nlm.nih.gov/pubmed/21219178">genetic and immunological basis</a> for why gluten is toxic in people with coeliac disease. Immune cells called T cells are the key mediators of damage in coeliac disease. These T cells are stimulated to cause damage by <a href="http://www.ncbi.nlm.nih.gov/pubmed/20650871">specific gluten fragments</a>, which have now been identified. </p>
<p>Such insights are allowing a variety of <a href="http://www.ncbi.nlm.nih.gov/pubmed/21401739">potential treatments</a> for coeliac disease to be explored, some of which will supplement and some of which could one day replace the gluten-free diet altogether.</p><img src="https://counter.theconversation.com/content/4928/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jason Tye-Din is affiliated with The Walter and Eliza Hall Institute and The Royal Melbourne Hospital. He receives funding from the NHMRC. He consults for ImmusanT Inc. and is co-inventor of patents related to the use of gluten peptides in diagnostics and therapies for coeliac disease.</span></em></p>The Neolithic Revolution introduced a whole range of new foods and proteins into the human digestive tract. But this phenomenal change created the perfect conditions for the rise of coeliac disease. While…Jason Tye-Din, Postdoctoral Scientist, Walter and Eliza Hall InstituteLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/8552011-05-31T20:58:13Z2011-05-31T20:58:13ZHow clean is too clean? Trust your gut instincts<figure><img src="https://images.theconversation.com/files/1386/original/Arlington_County_flickr_hygiene.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Could cleanliness be causing the rise of auto-immune diseases and allergies?</span> <span class="attribution"><span class="source">Arlington County/flickr</span></span></figcaption></figure><p>Could our obsession with cleanliness in our homes be working against us? </p>
<p>Advertisers fetishise germ-free kitchens and bathrooms where the threat of “harmful bacteria” is always lurking but can be eradicated with mop or a wipe.</p>
<p>Meanwhile, the media is full of alarming reports about the growing number of people with auto-immune and allergic diseases – the figure has more than doubled in the past 20 years. </p>
<p>One of the theories seeking to explain this exclusively Western epidemic is called the hygiene hypothesis: too much cleanliness is responsible for the immune abnormalities that cause auto-immune and allergic diseases. </p>
<p>But before we start embracing dirt, let’s stop and consider what we actually <em>know</em> about why so many people are getting these diseases and what needs to be done to change this.</p>
<h2>The hygiene hypothesis</h2>
<p>The hygiene hypothesis was developed in the United Kingdom to explain the rise in the number of people suffering from hay fever, which had been quite rare at the beginning of the 19th century. </p>
<p>Curiously, in the 1980s, <a href="http://www.ncbi.nlm.nih.gov/pubmed/2513902?dopt=Citation">UK children were found to be less likely to develop hay fever if they had older siblings</a>. Younger siblings did not have the same protective effect. </p>
<p>The original publication about this by David Strachan concluded that “allergic diseases were prevented by infection in early childhood, transmitted by unhygienic contact with older siblings, or acquired prenatally from a mother infected by contact with her older children.” </p>
<p>“Over the past century,” Strachan continued, “declining family size, improvements in household amenities, and higher standards of personal cleanliness have reduced the opportunity for cross infection in young families.” </p>
<p>The hygiene hypothesis rapidly gained support as an explanation for rising rates of allergic diseases. It explained why these diseases continued to rise despite – or indeed, because of – improvements in public health measures. </p>
<p>More recently, excessive hygiene has also been blamed for the rise in auto-immune diseases, including type 1 diabetes and multiple sclerosis. Inflammatory diseases such as Crohn’s disease and ulcerative colitis are also on the rise.</p>
<p>There appears to be plenty of evidence in support of the hypothesis: <a href="http://www.ncbi.nlm.nih.gov/pubmed/8557457?dopt=Citation">the steady increase in disease incidence</a> with rising – and therefore more hygienic – living standards in Western countries; the <a href="http://www.ncbi.nlm.nih.gov/pubmed/9068300?dopt=Citation">sharp increase of disease rates in children born to migrant families</a> after their arrival in Western countries; and the <a href="http://www.ncbi.nlm.nih.gov/pubmed/10784230?dopt=Citation">protective effect of factors such as early childcare</a>, which tends to reduce hygiene.</p>
<p>So, how does “hygiene” predispose people to immune-mediated disease? The short answer is that we don’t actually know.</p>
<p>While the migration studies, the rising incidence and the effect of birth order suggest an infectious cause, no one has pinpointed the responsible micro organism. </p>
<p>Suggestions include any number of common childhood infections, certain types of microbes and parasites prevalent in “dirt” or passed on by pets and farm animals, and even normal micro organisms present within our gut or on our skin.</p>
<p>Many studies have tested for correlations between <a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11597666">lifestyle factors, such as living on a farm, and the incidence of immune-mediated disease</a>. </p>
<p>But, as always with correlations, it is difficult to be sure which environmental/hygiene factors are responsible. </p>
<p>We know the infections involved aren’t the ones we vaccinate against, since vaccinations do not differentially affect siblings. And they didn’t produce a corresponding spike in immune-mediated diseases when they were introduced.</p>
<h2>An alternative approach to understanding immune-mediated disease</h2>
<p>One way of narrowing down the possible environmental/hygiene factors that cause immune-related disease is to approach the problem from the other end - by seeking to understand the immune system itself, and how environmental/hygiene factors could impact on its function.</p>
<p>For this approach, the discovery of a small but absolutely essential subset of T cells within the immune system has been vital. Regulatory T cells or Tregs (pronounced tee-regs) are unique in their ability to control unwanted immune responses, such as allergies and autoimmune diseases. </p>
<p>Children with non-functional Tregs die during infancy or childhood due to an over-active of the immune system. These deaths are caused by severe allergies and an aggressive autoimmune attack on many organs.</p>
<h2>Tregs – the intelligence officers of the immune system</h2>
<p>So how do Tregs work? Our own research at Sydney’s Centenary Institute has indicated that Tregs set the threshold for immune activation.</p>
<p>This means they allow the immune system to concentrate on dealing with serious infections by turning off responses to low-level microbial threats. </p>
<p>Tregs are the intelligence officers of the immune system, constantly interpreting the signals from the frontline where potentially harmful microbes are first encountered. </p>
<p>We propose that Tregs need to process a wide range of microbial information in order to appropriately set the immune threshold. When the threshold is at the right level, potentially threatening infections are perceived to be above the threshold and generate a rapid immune response. </p>
<p>Harmless environmental substances, on the other hand, fall below the threshold and are therefore ignored.</p>
<p>When Tregs are deprived of microbial information sources, they can set the threshold too low. Then the immune system mistakenly reacts to totally harmless substances. These include allergens, leading to allergic diseases such as hayfever, and the body’s own organs, leading to autoimmune diseases such as type 1 diabetes. </p>
<p>Since Tregs modulate the immune threshold in real time, even temporary disturbances in Treg function have the potential to cause detrimental allergic or autoimmune responses. </p>
<p>Like other immune cells, Tregs are distributed throughout the body, particularly at the sites where we are likely to encounter disease-causing microbes. </p>
<p>The most important site is the gastrointestinal tract (the GIT) where up to 90% of our immune cells are located. </p>
<h2>An inside-out focus for the immune system</h2>
<p>Somewhat paradoxically, your GIT, which is inside you, has by far the biggest area of interaction with the outside world - approximately 300 square metres compared to two square metres of skin. </p>
<p>It is also populated by a massive number of microbes: Your GIT contains between 10 and 100 trillion foreign organisms that are essential to your health. </p>
<p>The microbes that live within our guts are the obvious candidate for the source of harmless microbes to keep Tregs functioning normally. </p>
<p>Not only do they make up by far the majority of microbes that the immune system encounters on a daily basis, but they are established in early infancy and maintained throughout life in an essentially stable symbiotic relationship.</p>
<p>This dovetails neatly with the hygiene hypothesis because it explains how an infectious event early in life (colonisation of the gut with bowel flora) can produce a life-long effect on the immune system.</p>
<p>We are only just starting to understand our gut microbes, many of which cannot be cultured and were discovered only by sequencing their DNA. </p>
<p>There is now a massive sequencing effort – the <a href="http://www.hmpdacc.org/">Human Microbiome Project</a> - which, like the <a href="http://www.ornl.gov/sci/techresources/Human_Genome/home.shtml">Human Genome Project</a>, will serve as the foundation of further studies to understand our gut microbes.</p>
<h2>Hygiene and the GIT</h2>
<p>So, how does hygiene affect gut bacteria? First, we need to think about where the bacteria come from. The first and most important source is from our mothers during the birth process. </p>
<p>Babies born under very hygienic conditions, particularly by caesarian section, show a significant delay in colonisation by gut bacteria, and <a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=17604093">acquire significantly fewer different organisms</a>. </p>
<p>Thus, they start life with a relatively impoverished gut microbial ecosystem. </p>
<p>There is already evidence that the metabolic products of gut bacteria can have <a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11069568">crucial effects on development of allergic disease in infants</a>. </p>
<p>A recent report has also indicated <a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=21475195">effects on cardiovascular disease</a>. These reports come from developed countries that may already have lost significant components of a healthy gut microbial ecosystem due to generations of hygienic practices. </p>
<p>The question that is most pressing at the moment is: Will we be in time to preserve “natural” human gut ecosystems before the entire human population is irreversibly affected by “hygiene”?</p><img src="https://counter.theconversation.com/content/855/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Barbara Fazekas de St Groth receives funding from NHMRC and ARC.</span></em></p>Could our obsession with cleanliness in our homes be working against us? Advertisers fetishise germ-free kitchens and bathrooms where the threat of “harmful bacteria” is always lurking but can be eradicated…Barbara Fazekas de St Groth, Professor of Immunology, Centenary InstituteLicensed as Creative Commons – attribution, no derivatives.