tag:theconversation.com,2011:/us/topics/skin-microbiome-72507/articlesSkin microbiome – The Conversation2024-02-09T16:50:23Ztag:theconversation.com,2011:article/2153112024-02-09T16:50:23Z2024-02-09T16:50:23ZYour unique smell can provide clues about how healthy you are<figure><img src="https://images.theconversation.com/files/574043/original/file-20240207-19-o4ehc8.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5291%2C3516&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/happy-calm-teen-girl-enjoying-good-1325627765">fizkes/Shutterstock</a></span></figcaption></figure><p>Hundreds of chemicals stream from our bodies into the air every second. These chemicals release into the air easily as they have high vapour pressures, meaning they boil and turn into gases at room temperature. They give clues about who we are, and how healthy we are. </p>
<p>Since ancient Greek times, we’ve known that we smell differently when we are unwell. While we rely on blood analysis today, ancient Greek physicians used smell to diagnose maladies. If they took a whiff of your breath and described it as <em>fetor hepaticus</em> (meaning bad liver), it meant you could be headed for liver failure.</p>
<p>If a person’s whiff was sweet or fruity, physicians thought this meant that sugars in the digestive system were not being broken down, and that person had probably diabetes. Science has since shown the ancient Greeks were right – liver failure and <a href="https://tisserandinstitute.org/human-volatilome/">diabetes</a> and many <a href="https://link.springer.com/article/10.1007/s00216-023-04986-z">other diseases</a> including infectious diseases give your breath a distinctive smell.</p>
<p>In 1971, <a href="https://www.nobelprize.org/prizes/peace/1962/pauling/facts/">Nobel Laureate chemist Linus Pauling</a> <a href="https://edu.rsc.org/feature/breath-analysis/2020106.article#:%7E:text=The%20'modern%20era'%20of%20breath,in%20an%20average%20breath%20sample.">counted 250 different</a> gaseous chemicals in breath. These gaseous chemicals are called volatile organic compounds or VOCs. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/RzozmYPfCmM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Since Pauling’s discovery, other scientists have <a href="https://link.springer.com/article/10.1007/s40291-023-00640-7">discovered hundreds more VOCs</a> in our breath. We have learned that many of these VOCs have distinctive odours, but some have no odour that our noses can perceive. </p>
<p>Scientists believe that whether a VOC <a href="https://tisserandinstitute.org/human-volatilome/">has an odour</a> that our noses can detect or not, they can reveal information about how healthy someone is.</p>
<p>A Scottish man’s Parkinson’s disease onset was <a href="https://www.bbc.co.uk/news/uk-scotland-47627179">identified by his wife</a>, retired nurse Joy Milner, after she was convinced the way he smelled had changed, years before he was diagnosed in 2005. This discovery has <a href="https://www.manchester.ac.uk/discover/news/smell-of-skin-could-lead-to-early-diagnosis-for-parkinsons/">led to research programmes</a> involving Joy Milner to identify <a href="https://www.scientificamerican.com/article/a-supersmeller-can-detect-the-scent-of-parkinsons-leading-to-an-experimental-test-for-the-illness/">the precise smell</a> of this disease. </p>
<p>Dogs can <a href="https://www.nature.com/articles/d41586-022-01629-8">sniff out more diseases</a> than humans because of their more <a href="https://www.understandinganimalresearch.org.uk/news/the-science-of-sniffs-disease-smelling-dogs%20-%20I%20think%20the%20previous%20nature%20link%20has%20more%20credibility%20for%20here%20also">sophisticated olfactory talents</a>. But technological techniques, like <a href="https://www.britannica.com/science/mass-spectrometry">analytical tool mass spectrometry</a>, picks up even more subtle changes in VOC profiles that are being linked to <a href="https://www.thelancet.com/journals/ebiom/article/PIIS2352-3964(20)30100-6/fulltext">gut</a>, <a href="https://www-sciencedirect-com.dcu.idm.oclc.org/science/article/pii/S0165993618305168">skin</a> and <a href="https://err.ersjournals.com/content/28/152/190011">respiratory</a> diseases as well as neurological diseases like Parkinson’s. Researchers believe that one day some diseases will be diagnosed simply by breathing into a device. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Xjo2M-XMYfs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>Where do VOCs come from?</h2>
<p>Breath is not the only source of VOCs in the body. They are also emitted from skin, urine and faeces. </p>
<p>VOCs from skin are the result of millions of skin glands removing metabolic waste from the body, as well as waste generated by bacteria and other microbes that live on our skin. Sweating produces extra nutrients for these bacteria to metabolise which can result in particularly odorous VOCs. Odour from sweat only makes up a fraction of the scents from VOCs though.</p>
<p><a href="https://www.nature.com/articles/nrmicro.2017.157">Our skin</a> and also our gut microbiomes are made up from a delicate balance of these microbes. Scientists think <a href="https://journals.lww.com/co-gastroenterology/abstract/2015/01000/the_gut_microbiome_in_health_and_in_disease.12.aspx">they influence our health</a>, but we don’t yet understand a lot about how this relationship works. </p>
<p>Unlike the gut, the skin is relatively easy to study – you can collect skin samples from living humans without having to go deep into the body. <a href="https://www-sciencedirect-com.dcu.idm.oclc.org/science/article/pii/S1471492221002087">Scientists think</a> skin VOCs can offer insights into how the microbiome’s bacteria and the human body work together to maintain our health and protect us from disease.</p>
<p>In my team’s laboratory, <a href="https://iopscience.iop.org/article/10.1088/1752-7163/abf20a">we are investigating</a> whether the skin VOC signature can reveal different attributes of the person it belongs to. These signals in skin VOC signatures are probably how dogs distinguish between people by smell. </p>
<p>We are at a relatively early stage in this research area but we have shown that you can tell males from females based on how acidic the VOCs from skin are. We use mass spectrometry to see this as the average human nose is not sophisticated enough to detect these VOCs. </p>
<p>We can also predict a person’s age with reasonable accuracy to within a few years from their skin VOC profile. This is not surprising considering that oxidative stress in our bodies increases as we age.</p>
<p><a href="https://www.metabolismjournal.com/article/S0026-0495(00)80077-3/pdf">Oxidative stress</a> happens when your antioxidant levels are low and causes irreversible damage to our cells and organs. <a href="https://pubs.acs.org/doi/10.1021/jasms.3c00315">Our recent research</a> found by-products of this oxidative damage in skin VOC profiles. </p>
<p>Not only are these VOCs responsible for personal scent – they are used by plants, insects and animals as a communication channel. Plants are in a <a href="https://www.nature.com/articles/s41598-017-10975-x">constant VOC dialogue</a> with other organisms including pollinators, herbivores, other plants and their natural enemies such as harmful bacteria and insects. VOCs used for this back and forth dialogue are known as pheromones. </p>
<h2>What has science shown about love pheromones?</h2>
<p>In the animal kingdom, there is good evidence VOCs can act as aphrodisiacs. Mice for example have microbes which contribute to a particularly <a href="https://www.sciencedirect.com/science/article/pii/S0960982212012687">smelly compound called trimethylamine</a>, which allows mice to verify the species of a potential mate. <a href="https://www.sciencedirect.com/science/article/abs/pii/S0093691X21003083">Pigs</a> and <a href="https://www.nature.com/articles/4381097a">elephants</a> have sex pheromones too. </p>
<p>It is possible that humans also produce VOCs for attracting the perfect mate. Scientists have yet to fully decode skin – or other VOCs that are released from our bodies. But evidence for human love pheromones so far is <a href="https://www.science.org/content/article/do-human-pheromones-actually-exist">controversial at best</a>. <a href="https://www.newscientist.com/article/dn3835-colour-vision-ended-human-pheromone-use/">One theory suggests</a> that they were lost about 23 million years ago when primates developed full colour vision and started relying on their enhanced vision to choose a mate.</p>
<p>However, we believe that whether human pheromones exist or not, skin VOCs can reveal who and how we are, in terms of things like ageing, nutrition and fitness, fertility and even stress levels. This signature probably contains markers we can use to monitor our health and diagnose disease.</p><img src="https://counter.theconversation.com/content/215311/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Aoife Morrin receives funding from Science Foundation Ireland.</span></em></p>The science of smell is an exciting area of research.Aoife Morrin, Associate Professor of Analytical Chemistry, Dublin City UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2118612023-08-23T12:25:48Z2023-08-23T12:25:48ZAcne bacteria trigger cells to produce fats, oils and other lipids essential to skin health – new research<figure><img src="https://images.theconversation.com/files/543536/original/file-20230818-27-a54vaz.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2094%2C1416&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">There's more to the bacterium _Cutibacterium acnes_ than meets the eye.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/cropped-shot-of-the-face-of-a-young-woman-with-royalty-free-image/1581451668">Youngoldman/iStock via Getty Images Plus</a></span></figcaption></figure><p>The skin is the <a href="https://theconversation.com/the-skin-is-a-very-important-and-our-largest-organ-what-does-it-do-91515">largest organ of the body</a>, and it plays a crucial role as the first line of defense against pathogens and insults from the external environment. It provides important functions like temperature regulation and moisture retention. And despite the misconception that lipids harm your skin by causing oiliness and acne, they actually <a href="https://doi.org/10.1126/sciadv.adg6262">play a vital role</a> in maintaining the skin barrier.</p>
<p>Lipids – organic compounds that include <a href="https://www.khanacademy.org/science/biology/macromolecules/lipids/a/lipids">fats, oils, waxes and other types of molecules</a> – are essential components of the outermost layer of skin. Changes to the skin’s lipid composition can disrupt its ability to function as a protective barrier, leading to a <a href="https://doi.org/10.1046/j.0022-202x.2001.01455.x">range of skin diseases</a>, including eczema and psoriasis.</p>
<p>Human skin is colonized by <a href="https://doi.org/10.1038/nrmicro.2017.157">thousands of species of bacteria</a>. One of the most common microbes on the skin, <a href="https://doi.org/10.3390/microorganisms9030628"><em>Cutibacterium acnes</em>, or <em>C. acnes</em></a>, is well known for its potential involvement in causing acne, but its broader effects on skin health are less understood.</p>
<p>I am a <a href="https://profiles.ucsd.edu/samia.l.almoughrabie">researcher in dermatology</a> working in the <a href="https://dermatology.ucsd.edu/research/basic-science/gallo-lab/index.html">Gallo Lab</a> at the University of California, San Diego. My colleagues and I study how the skin defends the body against infections and the environment, with a particular focus on the skin microbiome, or the microbes living on the skin. In our recently published research conducted in collaboration with SILAB, a company developing active ingredients for skincare products, we found that <em>C. acnes</em> triggers certain skin cells to <a href="https://doi.org/10.1126/sciadv.adg6262">significantly increase production of lipids</a> that are important to maintaining the skin barrier.</p>
<h2>Skin bacteria and lipid synthesis</h2>
<p>To determine the role that bacteria play in lipid production, we exposed keratinocytes, the cells that <a href="https://www.britannica.com/science/human-skin/The-epidermis#">make up the epidermis</a>, to different bacteria naturally present on the skin and analyzed changes in lipid composition. </p>
<p>Of the common skin bacteria we tested, only <em>C. acnes</em> triggered an <a href="https://doi.org/10.1126/sciadv.adg6262">increase in lipid production</a> within these cells. More specifically, we found a threefold increase in total lipids, including ceramides, cholesterol, free fatty acids and especially triglycerides. Each of these lipid types are essential to maintaining the skin barrier, locking in moisture and protecting against damage. These findings suggest that <em>C. acnes</em> plays a distinctive role in the lipid skin regulation. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/MWE3U3FItlc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The skin microbiome contains bacteria and other microbes that help protect your body.</span></figcaption>
</figure>
<p>We found that <em>C. acnes</em> induced this increase in lipid production by producing a type of short-chain fatty acid called <a href="https://doi.org/10.1126/sciadv.adg6262">propionic acid</a>. Propionic acid creates an acidic skin environment that provides a number of benefits, including limiting pathogen growth, reducing staph infections and contributing to anti-inflammatory effects in the gut. </p>
<p>We also identified the <a href="https://doi.org/10.1126/sciadv.adg6262">specific gene and receptor</a> that regulate lipid synthesis through <em>C. acnes</em>. Blocking these components also blocked <em>C. acnes</em>-induced lipid synthesis.</p>
<p>In all, our findings highlight the substantial role that a common skin bacterium and its chemical byproducts play in shaping the composition of skin lipids.</p>
<h2>Reinforcing the skin barrier</h2>
<p>Our research suggests that propionic acid from <em>C. acnes</em> has <a href="https://doi.org/10.1126/sciadv.adg6262">multiple advantageous effects</a> on the skin barrier. For example, by increasing the lipid content in skin cells, propionic acid reduced water loss through the skin.</p>
<p>We also found that the lipids skin cells produce after exposure to <em>C. acnes</em> or propionic acid have antimicrobial effects against <em>C. acnes</em>. This suggests that the lipids <em>C. acnes</em> helps produce have a dual role: They not only control the presence of <em>C. acnes</em> on the skin but also contribute to the overall balance of the skin microbiome so one species of microbe doesn’t dominate the rest.</p>
<p>In the complex interplay between the skin and its microbial inhabitants, the ubiquitous <em>C. acnes</em> is emerging as an important player. Further research to better understand the skin microbiome may help lead to new treatments for skin conditions.</p><img src="https://counter.theconversation.com/content/211861/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Samia Almoughrabie 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>Bacteria and lipids get a bad rap for causing breakouts and oily skin. But both play an essential role in helping your skin barrier stay strong against pathogens and insults from the environment.Samia Almoughrabie, Postdoctoral Researcher in Dermatology, University of California, San DiegoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1951622023-04-05T12:23:16Z2023-04-05T12:23:16ZInnies, outies and omphalophobia: 7 navel-gazing questions about belly buttons answered<figure><img src="https://images.theconversation.com/files/517462/original/file-20230324-1164-blenfn.jpg?ixlib=rb-1.1.0&rect=0%2C374%2C3564%2C2404&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Your genes determine the look of your navel.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/young-girl-looking-at-her-belly-button-royalty-free-image/97766642">Mike Kemp/Tetra images via Getty Images</a></span></figcaption></figure><p><em>Everyone has one, but you might not know much about it. Here <a href="https://scholar.google.com/citations?user=iGYBbvEAAAAJ&hl=en&oi=ao">biologist Sarah Leupen</a>, who teaches human and comparative animal physiology, explains the ins and outs of belly buttons.</em></p>
<h2>1. Why do I even have a belly button?</h2>
<p>Your belly button, or navel – <a href="https://link.springer.com/chapter/10.1007/978-3-319-62383-2_1">clinically, your umbilicus</a> – is the permanent scar left from where your umbilical cord connected your circulatory system, when you were a fetus, to the placenta. Fetuses don’t breathe, eat or eliminate waste, so the placenta provides an exchange site for the mother to deliver oxygen and nutrients from her bloodstream to the fetus, as well as collecting its wastes to eliminate from her body.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517463/original/file-20230324-27-hz5plh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="closeup of umbilical cord stump on infant" src="https://images.theconversation.com/files/517463/original/file-20230324-27-hz5plh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517463/original/file-20230324-27-hz5plh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517463/original/file-20230324-27-hz5plh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517463/original/file-20230324-27-hz5plh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517463/original/file-20230324-27-hz5plh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517463/original/file-20230324-27-hz5plh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517463/original/file-20230324-27-hz5plh.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">Once the umbilical cord is cut, the stump dries up and falls off, revealing the baby’s navel.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-umbilical-cord-royalty-free-image/525032060">Wacharaphong/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<p>After the baby is born, the physician or other attendant cuts the cord and clamps off the stub, which then dries and falls off after about a week, leaving the point of connection – your belly button – remaining.</p>
<p>If the cord is not cut, as has been the practice in some times and places and as is becoming trendy again in others, it will close off after an hour or so, then naturally detach a few days after birth. Some health care practitioners are <a href="https://www.med.umich.edu/1libr/Pediatrics/LotusBirthHandout.pdf">concerned that this “lotus birth”</a> could be an infection risk, since the umbilical cord remains attached to the placenta, which is dead tissue once out of the mother’s body.</p>
<h2>2. If it’s a scar, why doesn’t it disappear over time?</h2>
<p>If you injure just the outer layers of your skin, as in a cut or burn, the scar will soon completely disappear, especially in young people. And newborns are very young people. But unlike in those situations, the umbilicus involves more tissue layers — not just the skin but the connective tissue underneath – so it makes sense it doesn’t just blend in with the rest of your abdominal wall once it’s healed.</p>
<p>What about some pretty complicated surgeries that don’t leave scars? Doctors perform many operations in ways that deliberately avoid scarring, which is not nature’s way. In fact, one way to minimize scarring for surgeries uses this existing scar – surgeons can take advantage of the navel as an incision site for <a href="https://doi.org/10.1053/j.sempedsurg.2011.05.003">removing your appendix</a> or <a href="https://doi.org/10.3109/13645706.2011.649039">gall bladder</a> or for <a href="https://doi.org/10.1016/j.soard.2010.12.007">weight-loss surgery</a>.</p>
<p>But if you don’t like the way your umbilical scar looks, plastic surgery to change its appearance, <a href="https://www.nytimes.com/2002/12/15/magazine/the-year-in-ideas-umbilicoplasty.html">called umbilicoplasty</a>, is possible. People sometimes take this cosmetic option after pregnancy or the removal of a piercing, or just to make an “outie” into an “innie.”</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/515931/original/file-20230316-19-jzc793.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="smooth belly with an outie belly button" src="https://images.theconversation.com/files/515931/original/file-20230316-19-jzc793.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/515931/original/file-20230316-19-jzc793.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=381&fit=crop&dpr=1 600w, https://images.theconversation.com/files/515931/original/file-20230316-19-jzc793.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=381&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/515931/original/file-20230316-19-jzc793.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=381&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/515931/original/file-20230316-19-jzc793.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=479&fit=crop&dpr=1 754w, https://images.theconversation.com/files/515931/original/file-20230316-19-jzc793.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=479&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/515931/original/file-20230316-19-jzc793.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=479&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Outies are much less common than innies.</span>
<span class="attribution"><a class="source" href="https://flic.kr/p/8kd8nw">Zeev Barkan/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>3. But why do some people have outies, anyway?</h2>
<p>The look of your belly button is not related to the location of the clamp or where your doctor cut the cord.</p>
<p>Outies are simply an example of <a href="https://learn.genetics.utah.edu/content/basics/observable/">normal human variation</a>, like the way some people have curly hair or dimples. When the tip of the umbilical cord’s remnant pokes out past the skin around it, you have an outie; <a href="http://dx.doi.org/10.1007/978-3-319-62383-2_22">about 10% of people have these</a>. Any concave navel is called an “innie” and a convex one an “outie.”</p>
<p>Sometimes outies can be caused by an umbilical hernia in the baby or another medical problem, but most of it is just due to what your genes encoded. You might also temporarily have an outie during late pregnancy, when the abdominal pressure from the growing fetus stretches your navel and may push it out.</p>
<h2>4. How deep does it go?</h2>
<p>You can probably easily probe the depth of your own navel – there are no hidden recesses there. What’s under it is the same as what’s under the skin of the rest of your abdomen: your abdominal muscles, to which the navel is attached by a short umbilical stalk, and the peritoneum, the membrane that lines the abdominal cavity. Under that lie your guts – that is, your intestines and other abdominal organs. If you keep following this imaginary journey back, you’ll get to your spine – the belly button is usually lined up <a href="http://dx.doi.org/10.1007/978-3-319-62383-2_22">between the third and fourth lumbar vertebrae</a> (L3 and L4).</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/WkgjK3Kp6Uw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Learn how to find your pet’s belly button.</span></figcaption>
</figure>
<h2>5. Do other animals have belly buttons?</h2>
<p>Because the navel is a scar from where the umbilical cord connected the fetus to the placenta, all placental mammals have them. That includes all mammals except <a href="https://www.britannica.com/animal/marsupial">marsupials</a> (like kangaroos and possums) and <a href="https://www.britannica.com/animal/monotreme">monotremes</a> (like platypuses and echidnas).</p>
<p>Your cat or dog or guinea pig does have a belly button, but because it’s a flatter scar than a person’s rather than a concave one, and is covered in fur, you might have missed it.</p>
<h2>6. Is there anything besides lint in there?</h2>
<p>Like any concave surface, if you have an innie, it probably gathers bits of debris occasionally. Your navel also has microbiota, just like the rest of your skin. Because it’s pretty protected from soap and abrasion, a more <a href="https://en.wikipedia.org/wiki/Skin_flora#Umbilical_microbiome">stable and diverse bacterial community</a> lives in your navel than elsewhere on your skin’s surface.</p>
<p>The innovative <a href="http://robdunnlab.com/projects/belly-button-biodiversity/">Belly Button Biodiversity project</a> at North Carolina State University has revealed a lot about these little friends. The researchers found <a href="https://doi.org/10.1371/journal.pone.0047712">over 2,000 species of bacteria</a> in the first 60 belly buttons they investigated.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1422846688276979715"}"></div></p>
<p>It looks like most people have a set of eight common belly button bacteria, but the project is discovering new ones all the time.</p>
<h2>7. Why do belly buttons gross out some people?</h2>
<p>There hasn’t really been much research into why some people find belly buttons to be repulsive.</p>
<p>It may overlap with <a href="https://healthresearchfunding.org/fear-bellybuttons/">omphalophobia</a>, the fear of belly buttons and touching them. There’s no specific treatment beyond the therapy or anti-anxiety medications a doctor might prescribe for any other phobia.</p>
<p>Whatever your feelings about belly buttons, they’re harmless. What’s more, they’re part of your evolutionary legacy as a mammal, the group of animals so invested in their offspring that they invented a way to deliver nutrients and oxygen, the mother’s bread and breath, straight into their developing young. Your navel can be a reminder of that first life-sustaining care you received from another person before you were even born.</p><img src="https://counter.theconversation.com/content/195162/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sarah Leupen 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>All mammals who get nutrients from their parent via a placenta before birth are left with a belly button. It’s a visual reminder of this original connection.Sarah Leupen, Principal Lecturer in Biological Sciences, University of Maryland, Baltimore CountyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1858332022-06-30T15:20:20Z2022-06-30T15:20:20ZViruses can change your scent to make you more attractive to mosquitoes, new research in mice finds<figure><img src="https://images.theconversation.com/files/471659/original/file-20220629-13-56a1wn.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2129%2C1402&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Mosquito-borne diseases are estimated to cause over 1 million deaths a year.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/biting-mosquito-royalty-free-image/960349766">mrs/Moment via Getty Images</a></span></figcaption></figure><p>Mosquitoes are the <a href="https://www.cdc.gov/globalhealth/stories/2019/world-deadliest-animal.html">world’s deadliest animal</a>. <a href="https://doi.org/10.1016/B978-0-12-812365-2.00003-2">Over 1 million deaths</a> per year are attributed to <a href="https://www.cdc.gov/niosh/topics/outdoor/mosquito-borne/default.html">mosquito-borne diseases</a>, including malaria, yellow fever, dengue fever, Zika and chikungunya fever.</p>
<p>How mosquitoes seek out and feed on their hosts are important factors in how a virus circulates in nature. Mosquitoes spread diseases by acting as carriers of viruses and other pathogens: A mosquito that bites a person infected with a virus can acquire the virus and pass it on to the next person it bites. </p>
<p>For immunologists and infectious disease researchers <a href="https://scholar.google.com/citations?user=6iEQIeIAAAAJ&hl=en">like me</a>, a better understanding of how a virus interacts with a host may offer new strategies for preventing and treating mosquito-borne diseases. In our <a href="https://doi.org/10.1016/j.cell.2022.05.016">recently published study</a>, my colleagues and I found that some viruses can alter a person’s body odor to be more attractive to mosquitoes, leading to more bites that allow a virus to spread. </p>
<h2>Viruses change host odors to attract mosquitoes</h2>
<p>Mosquitoes locate a potential host through <a href="https://doi.org/10.1016/j.cub.2015.07.057">different sensory cues</a>, such as your <a href="https://doi.org/10.7554/eLife.11750">body temperature</a> and the <a href="https://doi.org/10.1017/S0007485300007811">carbon dioxide</a> emitted from your breath. Odors also play a role. Previous lab research has found that mice <a href="https://doi.org/10.1073%2Fpnas.1405617111">infected with malaria</a> have changes in their scents that make them more attractive to mosquitoes. With this in mind, my colleagues and I wondered if other mosquito-borne viruses, such as dengue and Zika, can also change a person’s scent to make them more attractive to mosquitoes, and whether there is a way to prevent these changes.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/j6MrN9o0BfA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A number of factors can make you more attractive to mosquitoes, including the odors you emit.</span></figcaption>
</figure>
<p>To investigate this, we placed mice infected with the dengue or Zika virus, uninfected mice and mosquitoes in one of three arms of a glass chamber. When we applied airflow through the mouse chambers to funnel their odors toward the mosquitoes, we found that more mosquitoes chose to fly toward the infected mice over the uninfected mice.</p>
<p>We ruled out carbon dioxide as a reason for why the mosquitoes were attracted to the infected mice, because while Zika-infected mice emitted less carbon dioxide than uninfected mice, dengue-infected mice did not change emission levels. Likewise, we ruled out body temperature as a potential attractive factor when mosquitoes did not differentiate between mice with elevated or normal body temperatures. </p>
<p>Then we assessed the role of body odors in the mosquitoes’ increased attraction to infected mice. After placing a filter in the glass chambers to prevent mice odors from reaching the mosquitoes, we found that the number of mosquitoes flying toward infected and uninfected mice were comparable. This suggests that there was something about the odors of the infected mice that drew the mosquitoes toward them.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/471703/original/file-20220629-17-7vpcaf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Gloved hand holding two test tubes full of mosquitoes in a lab" src="https://images.theconversation.com/files/471703/original/file-20220629-17-7vpcaf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471703/original/file-20220629-17-7vpcaf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471703/original/file-20220629-17-7vpcaf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471703/original/file-20220629-17-7vpcaf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471703/original/file-20220629-17-7vpcaf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471703/original/file-20220629-17-7vpcaf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471703/original/file-20220629-17-7vpcaf.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">Volunteering in a mosquito study may require a few bites.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/cropped-hand-holding-mosquito-in-test-tube-at-royalty-free-image/1026135942">Panyawat Boontanom/EyeEm via Getty Images</a></span>
</figcaption>
</figure>
<p>To identify the odor, we isolated 20 different gaseous chemical compounds from the scent emitted by the infected mice. Of these, we found three to stimulate a significant response in mosquito antennae. When we applied these three compounds to the skin of healthy mice and the hands of human volunteers, only one, <a href="https://doi.org/10.1111/eea.12297">acetophenone</a>, attracted more mosquitoes compared to the control. We found that infected mice produced 10 times more acetophenone than uninfected mice. </p>
<p>Similarly, we found that the odors collected from the armpits of dengue fever patients contained more acetophenone than those from healthy people. When we applied the dengue fever patient odors on one hand of a volunteer and a healthy person’s odor on the other hand, mosquitoes were consistently more attracted to the hand with dengue fever odors.</p>
<p>These findings imply that the dengue and Zika viruses are capable of increasing the amount of acetophenone their hosts produce and emit, making them even more attractive to mosquitoes. When uninfected mosquitoes bite these attractive hosts, they may go on to bite other people and spread the virus even further.</p>
<h2>How viruses increase acetophenone production</h2>
<p>Next, we wanted to figure out how viruses were increasing the amount of mosquito-attracting acetophenone their hosts produce. <a href="https://doi.org/10.1111/eea.12297">Acetophenone</a>, along with being a chemical commonly used as a <a href="https://pubchem.ncbi.nlm.nih.gov/compound/Acetophenone">fragrance</a> in perfumes, is also a metabolic byproduct commonly produced by certain bacteria living on the skin and in the intestines of both people and mice. So we wondered if it had something to do with changes in the type of bacteria on the skin.</p>
<p>To test this idea, we removed either the skin or intestinal bacteria from infected mice before exposing them to mosquitoes. While mosquitoes were still more attracted to infected mice with depleted intestinal bacteria compared to uninfected mice, they were significantly less attracted to infected mice with depleted skin bacteria. These results suggest that skin microbes are an essential source of acetophenone. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/471714/original/file-20220629-20-3iu2bq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Long chains of Bacillus megatherium under a microscope" src="https://images.theconversation.com/files/471714/original/file-20220629-20-3iu2bq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471714/original/file-20220629-20-3iu2bq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471714/original/file-20220629-20-3iu2bq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471714/original/file-20220629-20-3iu2bq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471714/original/file-20220629-20-3iu2bq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=539&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471714/original/file-20220629-20-3iu2bq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=539&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471714/original/file-20220629-20-3iu2bq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=539&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Viruses can alter the skin microbiome to increase the presence of bacteria like <em>Bacillus</em>, which produce mosquito-attracting odors.</span>
<span class="attribution"><a class="source" href="https://flic.kr/p/aLPmBV">Marc Perkins/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>When we compared the skin bacteria compositions of infected and uninfected mice, we identified that a common type of rod-shaped bacteria, <a href="https://www.britannica.com/science/bacillus-bacteria"><em>Bacillus</em></a>, was a major acetophenone producer and had significantly increased numbers on infected mice. This meant that the dengue and Zika viruses were able to change their host’s odor by altering the microbiome of the skin.</p>
<h2>Reducing mosquito-attracting odors</h2>
<p>Finally, we wondered if there was a way to prevent this change in odors. </p>
<p>We found one potential option when we observed that infected mice had decreased levels of an important microbe-fighting molecule produced by skin cells, called RELMα. This suggested that the dengue and Zika viruses suppressed production of this molecule, making the mice more vulnerable to infection.</p>
<p><a href="https://doi.org/10.1016/j.chom.2019.04.004">Vitamin A</a> and its related chemical compounds are known to strongly boost production of RELMα. So we fed a vitamin A derivative to infected mice over the course of a few days and measured the amount of RELMα and <em>Bacillus</em> bacteria present on their skin, then exposed them to mosquitoes.</p>
<p>We found that infected mice treated with the vitamin A derivative were able to restore their RELMα levels back to those of uninfected mice, as well as reduce the amount of <em>Bacillus</em> bacteria on their skin. Mosquitoes were also no more attracted to these treated, infected mice than uninfected mice. </p>
<p>Our next step is to replicate these results in people and eventually apply what we learn to patients. <a href="https://www.who.int/data/nutrition/nlis/info/vitamin-a-deficiency">Vitamin A deficiency</a> is common in developing countries. This is especially the case in sub-Saharan Africa and Southeast Asia, where mosquito-transmitted viral diseases are prevalent. Our next steps are to investigate whether dietary vitamin A or its derivatives could reduce mosquito attraction to people infected with Zika and dengue, and subsequently reduce mosquito-borne diseases in the long term.</p><img src="https://counter.theconversation.com/content/185833/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Penghua Wang receives funding from the National Institutes of Health, Department of Health and Human Services, United States organization. He is a regular member of American Association of Immunologists, American Society for Virology, The Society of Chinese Bioscientists in America. </span></em></p>Certain viruses like dengue and Zika can make their hosts smell tastier to mosquitoes. Luckily, vitamin A and its derivatives may help combat these odor changes.Penghua Wang, Assistant Professor of Immunology, University of ConnecticutLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1774542022-04-22T01:35:23Z2022-04-22T01:35:23ZWhat is toe jam? From harmless gunk to a feast for bugs<figure><img src="https://images.theconversation.com/files/456809/original/file-20220407-14-flir0u.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1000%2C664&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-girls-toes-healthy-beautiful-wellgroomed-1371423317">Shutterstock</a></span></figcaption></figure><p><a href="https://www.healthline.com/health/all-about-toe-jam">Toe jam</a> can be a source of fascination, disgust or barely noticed. It can be a sign you need to wash your feet or rethink your choice of footwear. It can also lead to major health issues.</p>
<p>Toe jam, the gunk and debris between your toes, has even made it to a Beatles song.</p>
<p>But it was unlikely John Lennon was thinking about foot hygiene when he wrote the lyrics to the second verse of <a href="https://genius.com/The-beatles-come-together-lyrics">Come Together</a>:</p>
<blockquote>
<p>He wear no shoeshine, he got toe-jam football</p>
<p>He got monkey finger, he shoot Coca-Cola</p>
<p>He say, ‘I know you, you know me’</p>
<p>One thing I can tell you is you got to be free.</p>
</blockquote>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/uSM5MpKSnqE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Yes, The Beatles really mentioned toe jam in Come Together (YouTube).</span></figcaption>
</figure>
<h2>What is toe jam, actually?</h2>
<p>Toe jam isn’t a medical term. There is no formal medical term to describe the dead skin cells, sweat, sock lint and dirt that combine in the small and often cramped spaces between our toes.</p>
<p>Toe jam can have the consistency of soft cheese or cake crumbs. It can smell or be odourless. And its colour can range from white to grey-brown.</p>
<p>You’re more likely to create toe jam if you wear closed-in shoes when it’s hot, or gumboots that don’t allow sweat to evaporate.</p>
<p>Poor foot hygiene will certainly make it more likely you’ll develop toe jam. That’s because sweaty debris accumulates in between the toes if you don’t pay attention to cleaning these areas in the shower or bath.</p>
<p>Toe jam may also be more likely if your feet sweat a lot for other reasons. For instance, we know <a href="https://www.racgp.org.au/afp/2009/september/sweaty-smelly-hands-and-feet">sweaty feet</a> can be a problem for children and adolescents, who have more active sweat glands. And some people have a serious medical condition called <a href="https://www.sweathelp.org/index.php">hyperhidrosis</a>, where they sweat excessively.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/anhidrosis-why-some-people-apparently-like-prince-andrew-just-cant-sweat-127280">Anhidrosis: why some people – apparently like Prince Andrew – just can't sweat</a>
</strong>
</em>
</p>
<hr>
<h2>Is toe jam like athlete’s foot?</h2>
<p>The collection of sweat and dead skin between toes provides bacteria living naturally on our skin the chance to thrive. </p>
<p>These bacteria, which include ones in the genus <em>Brevibacterium</em>, feed on sweat, releasing molecules that give the characteristic “cheesy” <a href="https://theconversation.com/why-do-feet-stink-by-the-end-of-the-day-125037">smell of sweaty feet</a>. Brevibacterium is also used to ripen some cheeses.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/457034/original/file-20220408-19484-ox4ymj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Soft cheese, cut in slices" src="https://images.theconversation.com/files/457034/original/file-20220408-19484-ox4ymj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457034/original/file-20220408-19484-ox4ymj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=436&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457034/original/file-20220408-19484-ox4ymj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=436&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457034/original/file-20220408-19484-ox4ymj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=436&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457034/original/file-20220408-19484-ox4ymj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=547&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457034/original/file-20220408-19484-ox4ymj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=547&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457034/original/file-20220408-19484-ox4ymj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=547&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">No wonder your feet smell cheesy if you don’t wash them properly.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/cheeseboard-sliced-yellow-limburger-cheese-top-1343151806">Shutterstock</a></span>
</figcaption>
</figure>
<p>This warm and damp environment is also a perfect site for <a href="https://www.healthdirect.gov.au/tinea">tinea pedis</a>, a fungal skin infection you might know as athlete’s foot. </p>
<p>Signs of tinea might be soggy white skin between your toes, which can be itchy, and red areas, a sign of skin damage. <a href="https://dermnetnz.org/topics/athletes-foot">Damaged skin</a> between toes might develop small fluid-filled blisters and may also bleed if the weak skin is torn.</p>
<p>So while toe jam isn’t the same as tinea, it might provide the perfect conditions for the fungus to grow.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-do-feet-stink-by-the-end-of-the-day-125037">Why do feet stink by the end of the day?</a>
</strong>
</em>
</p>
<hr>
<h2>How serious is toe jam?</h2>
<p>Generally, toe jam is a minor health problem. You can <a href="https://www.racgp.org.au/getattachment/233c1fdf-8802-471e-9828-f792110c30d1/Sweaty-smelly-hands-and-feet.aspx">manage it</a> with good foot hygiene. And if you develop tinea, you can use a short course of an anti-fungal treatment you can buy from a pharmacy (see below).</p>
<p>It is quite a different prospect, however, for a person living with a chronic disease such as diabetes, someone who has poor vision (so can’t see toe jam or its complications developing), or who may be unable to reach their feet due to limited mobility.</p>
<p>Diabetes not well controlled with diet and exercise, or drugs, increases the <a href="https://www.diabetesfeetaustralia.org/">risk</a> of a person having reduced blood flow (peripheral arterial disease) and reduced feeling in their feet (sensory neuropathy). </p>
<p>Broken skin between the toes caused by tinea can become infected rapidly, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3248359/">increasing the risk</a> of:</p>
<ul>
<li><p>infection spreading to the foot and leg (cellulitis)</p></li>
<li><p>infection of the bone (osteomyelitis)</p></li>
<li><p>gangrene (dead tissue caused by lack of blood flow)</p></li>
<li><p>amputation of a toe, part of the foot or leg. </p></li>
</ul>
<p>So early identification of tinea in a vulnerable person is especially important to prevent complications.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/life-on-us-a-close-up-look-at-the-bugs-that-call-us-home-25754">Life on Us: a close-up look at the bugs that call us home</a>
</strong>
</em>
</p>
<hr>
<h2>4 ways to avoid problems</h2>
<p>Here are our four tips to avoid problems with toe jam, including developing tinea and its complications:</p>
<ol>
<li><p>wash the spaces between your toes and dry them carefully after a shower or bath, and after swimming. Gyms and swimming pools are a common place to pick up a fungal infection on your feet so it’s a good idea to wear thongs to reduce the risk of tinea</p></li>
<li><p>if possible, avoid wearing footwear that doesn’t allow sweat to evaporate (such as closed-in shoes made of synthetic material and gumboots). Going barefoot, when there is no risk of injury, will also allow sweat to evaporate</p></li>
<li><p>treat sweaty feet by using an <a href="https://www.racgp.org.au/afp/2009/september/sweaty-smelly-hands-and-feet">anti-perspirant</a> containing aluminium chloride. More severe cases of hyperhidrosis may be managed using drugs, such as <a href="https://www.dermcoll.edu.au/atoz/plantar-hyperhidrosis/">Botox</a> injections to the feet. Fungal infections (<a href="https://dermnetnz.org/topics/tinea-pedis">tinea</a>) should be treated using over-the-counter antifungal creams such a terbinafine or clotrimazole. Resistant infections might require a course of prescribed antifungal medicines</p></li>
<li><p>pay attention to <a href="https://www.healthline.com/health/all-about-toe-jam#when-to-see-a-doctor">signs</a> indicating an infection is spreading from the foot. These could be pain and swelling in the toes, or red streaks along the foot and up the leg. This requires an urgent visit to a podiatrist or doctor.</p></li>
</ol>
<h2>Footnote</h2>
<p>Lennon mentions a “walrus gumboot” in verse three of Come Together. The final line of verse two says “you got to be free”. The cover of The Beatles album Abbey Road shows Paul McCartney walking barefoot (second from the left).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/457039/original/file-20220408-18-vvxes4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Beatles album Abbey Road propped up behind turntable playing a record" src="https://images.theconversation.com/files/457039/original/file-20220408-18-vvxes4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457039/original/file-20220408-18-vvxes4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457039/original/file-20220408-18-vvxes4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457039/original/file-20220408-18-vvxes4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457039/original/file-20220408-18-vvxes4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457039/original/file-20220408-18-vvxes4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457039/original/file-20220408-18-vvxes4.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">Maybe The Beatles were onto something.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/naples-italy-10032019-fabulous-beatles-depicted-1334880947">Imma Gambardella/Shutterstock</a></span>
</figcaption>
</figure>
<p>Maybe the Beatles did know a thing or two about toe jam and foot health.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/beatles-abbey-road-at-50-is-a-marker-of-how-pop-music-grew-up-in-the-1960s-124433">Beatles: Abbey Road at 50 is a marker of how pop music grew up in the 1960s</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/177454/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Caroline Robinson is affiliated with the Australasian Council of Podiatry Deans and the Australian Podiatry Association.</span></em></p><p class="fine-print"><em><span>Luke Donnan is affiliated with the Australasian Council of Podiatry Deans and the Australian Podiatry Association.</span></em></p>Toe jam was mentioned in a song by The Beatles. Maybe they knew a thing or two about foot hygiene.Caroline Robinson, Associate Professor Podiatry, Charles Sturt UniversityLuke Donnan, Lecturer in Podiatry, Charles Sturt UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1458932020-09-10T14:49:08Z2020-09-10T14:49:08ZLive bacteria spray is showing promise in treating childhood eczema<figure><img src="https://images.theconversation.com/files/357301/original/file-20200909-24-155gm7p.jpg?ixlib=rb-1.1.0&rect=25%2C25%2C4249%2C2805&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A physician examines a 7-month-old infant with eczema. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/photo-essay-at-the-department-of-dermatology-at-the-bocage-news-photo/151054958?adppopup=true">BSIP/UIG Via Getty Images</a></span></figcaption></figure><p>Here’s a shorthand way to think of my research: Using bugs as drugs may one day bring hope to soaps. </p>
<p>Patients with <a href="https://www.niaid.nih.gov/diseases-conditions/eczema-atopic-dermatitis">atopic dermatitis</a>, more commonly known as eczema, suffer from dry, itchy skin and rashes, and have a higher risk of developing hay fever, asthma and food allergies. The cause of eczema is still unknown, but studies completed by <a href="https://doi.org/10.1172/jci.insight.120608">my team</a> and <a href="https://doi.org/10.1126/scitranslmed.aah4680">others</a> continue to suggest that manipulating the skin microbiome – the community of all the bacteria and other microorganisms living on the surface of the skin – may offer therapeutic benefits to patients. </p>
<p><a href="https://stm.sciencemag.org/content/12/560/eaaz8631">We hypothesized that if we directly sprayed live bacteria</a> named <em><a href="https://insight.jci.org/articles/view/120608">Roseomonas mucosa</a></em> - a naturally occurring skin microbe - on the skin of patients with eczema, those healthy bacteria might make for healthy skin. </p>
<h2>How might the bacteria help?</h2>
<p>I am an allergy and immunology physician who <a href="https://www.niaid.nih.gov/research/ian-myles-md-mph">explores the intersection of the microbiome</a>, the skin and the environment in order to identify why allergic diseases have become more common in modern times.</p>
<p>All our scrapes, scratches, scrubbing and soaps take a toll on our skin. The natural oils that our skin makes are <a href="https://doi.org/10.1016/j.jdermsci.2019.12.002">part of the normal processes</a> the skin uses to repair itself after these insults. </p>
<p>Using human cells and mice, my colleagues and I were able to uncover additional evidence that oils from bacteria that reside on the skin may also play a role. The oils from <em>Roseomonas</em> induce a <a href="https://doi.org/10.1016/j.cell.2016.06.028">specific skin repair pathway</a>, in part through influencing molecules that are more frequently associated with our nerves than our skin. These oils also <a href="https://doi.org/10.1172/jci.insight.86955">help kill</a> <em>Staphylococcus aureus</em>, a bacteria known to make <a href="https://doi.org/10.1111/bjd.15409">eczema worse</a>. </p>
<h2>What do patients want?</h2>
<p>Our hope is that a topical treatment using this bacteria will be an improvement over current eczema treatments.</p>
<p>In 2013, the U.S. Food and Drug Administration (FDA) began soliciting direct input from patients and patient advocacy groups for events known as <a href="https://www.fda.gov/industry/prescription-drug-user-fee-amendments/fda-led-patient-focused-drug-development-pfdd-public-meetings">Patient-Focused Drug Development</a> meetings (or PFDD, for short). </p>
<p>In September of 2019, the FDA conducted a <a href="https://www.aafa.org/media/2628/more-than-skin-deep-voice-of-the-patient-report.pdf">PFDD for eczema</a>. One of the major findings was that itching was the symptom of primary concern for patients and their families. This stands in contrast with the FDA’s current practice of approving new drugs based solely on the improvement in how bad the rash looks, instead of how bad the rash feels. Patients also reported a high rate of complications from their current treatments and expressed particular concerns about using topical steroids. </p>
<p><a href="https://www.aafa.org/media/2628/more-than-skin-deep-voice-of-the-patient-report.pdf">Overall</a>, patients said that eczema substantially decreased their quality of life because of the need to apply medications frequently. Eczema also drained their emotions and deprived them of sleep due to unmanageable itching in either them or their children.</p>
<p><a href="https://theconversation.com/applying-live-bacteria-to-skin-improves-eczema-95920">Two years ago</a>, my colleagues and I reported our results from 10 adults and five children who were at least 9 years old. </p>
<p>Since eczema most often afflicts children who are younger than 7 years old, our newest study enrolled an additional 15 children as young as 3 years old. Overall, <a href="https://stm.sciencemag.org/content/12/560/eaaz8631">our patients achieved a 60-75% improvement</a> in their rash and itch by applying <em>Roseomonas</em> two to three times per week for 4 months. </p>
<p>Patients and their families also reported needing to apply topical steroids less often and a better quality of life as they slept more and itched less. One patient complained of mild itching during the minute or so it took the spray to dry on their arms, but there were no other complaints related to treatment. Thus, taken together with some of our <a href="https://pubmed.ncbi.nlm.nih.gov/30719426/">safety studies in mice</a>, <em>Roseomonas</em> continues to appear safe.</p>
<h2>Is this a cure?</h2>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/357306/original/file-20200909-20-jr720w.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/357306/original/file-20200909-20-jr720w.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/357306/original/file-20200909-20-jr720w.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=467&fit=crop&dpr=1 600w, https://images.theconversation.com/files/357306/original/file-20200909-20-jr720w.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=467&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/357306/original/file-20200909-20-jr720w.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=467&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/357306/original/file-20200909-20-jr720w.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=587&fit=crop&dpr=1 754w, https://images.theconversation.com/files/357306/original/file-20200909-20-jr720w.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=587&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/357306/original/file-20200909-20-jr720w.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=587&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Left: Inner elbow of a child with eczema before <em>Roseomonas mucosa</em> therapy. Right: The same patients after four months of treatment.</span>
<span class="attribution"><span class="source">NIAID</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>One of the more promising findings of our new study was that patients’ symptoms improved for up to eight months after stopping the bacterial spray medication. The advantage of using live bacteria is that the microbes can take up residence on the skin. We found that the bacteria lived on the skin at least eight months after treatment and likely continued to provide clinical benefit without the need for constant application.</p>
<p>While not cured, many patients in the study described their symptoms and “muted.” Their typical day was better than ever, and while eczema flares still occurred, they were less frequent and less severe. Theoretically, applying our treatment as soon as symptoms manifest might prevent future disease and thus be “curative” – however, for now, such thinking is speculation. </p>
<p>Yet, even if <em>Roseomonas</em> is more treatment than cure, our findings are still directly aligned with <a href="https://www.aafa.org/media/2628/more-than-skin-deep-voice-of-the-patient-report.pdf">the goals laid out in the PFDD</a>: “sustained relief from itch,” a reduced need for topical steroids and an overall improved ability to “go about daily life.”</p>
<h2>What comes next?</h2>
<p>Starting this month, we are expanding our clinical <em>Roseomonas</em> study to include many more patients in a <a href="https://clinicaltrials.gov/ct2/show/NCT04504279">placebo-controlled trial</a>. <a href="https://www.atopicdermclinicaltrial.com">In the new clinical study</a>, half the 120 or more patients that enroll will get our <em>Roseomonas</em> spray while the other half will get only a sugar water spray. </p>
<p>The knowledge that bacteria like <em>Roseomonas</em> can help patients with eczema will also allow us to examine which environmental exposures might harm these microbes. According to a <a href="https://www.epa.gov/assessing-and-managing-chemicals-under-tsca/introduction-chemview">2016 report</a> from the Environmental Protection Agency, there are over 8,700 chemicals on the U.S. market. Not all of these are common and not all are used on the skin, but the number of possible combinations and concentrations of chemicals we may expose our skin to on a daily basis could be near infinite. </p>
<p>By systematically evaluating which exposures help, which hurt and which are benign, we may be able to “bathe smarter” and identify the best way to keep ourselves clean without disrupting the balance of the bacteria that keep us healthy.</p><img src="https://counter.theconversation.com/content/145893/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ian Myles 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>Can a naturally occurring skin microbe help millions who suffer from eczema?Ian Myles, Head, Epithelial Therapeutics Unit, National Institute of Allergy and Infectious DiseasesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1292152020-01-03T13:48:46Z2020-01-03T13:48:46Z5 things you can do to make your microbiome healthier<figure><img src="https://images.theconversation.com/files/308212/original/file-20191223-11929-1kqe73v.jpg?ixlib=rb-1.1.0&rect=31%2C31%2C5145%2C3414&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Fresh fruits and vegetables are good for you and your gut microbes.
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/variety-fresh-raw-organic-fruits-vegetables-383309998">Teri Virbickis/Shutterstock.com</a></span></figcaption></figure><p>It’s common for people to focus on their health at the start of the year. But few consider the well being of the microbes that live inside the human gut – the microbiome – which are vital to an individual’s good health.</p>
<p>How important are these bacteria? <a href="https://dx.doi.org/10.1371%2Fjournal.pbio.1002533">There are as many bacterial cells in us as there are human cells</a>, and they help control everything from <a href="https://doi.org/10.1136/bmj.j5145">inflammation</a> and the <a href="https://doi.org/10.1038/s41568-019-0155-3">development and treatment of cancer</a> to <a href="https://doi.org/10.1017/S0029665114001700">how much energy we get from our foods</a> and perhaps even <a href="https://doi.org/10.1371/journal.pbio.2000862">what foods we crave</a> and <a href="https://doi.org/10.1038/s41564-018-0337-x">our moods</a>. When our microbiome becomes unbalanced, often indicated when certain species or groups of bacteria become overly abundant, these functions can be disrupted, contributing to the development of a wide range of diseases such as obesity, cancer, inflammatory bowel disease and many others.</p>
<p>Our gut microbes are also responsible for gas production when we eat new foods as those microbes adapt to this new nutrient source in their environment. So it is clear we want to have a healthy microbiome, but what is that? </p>
<p>There is a lot of debate regarding what exactly constitutes a healthy community of gut microbes, but one thing has become clear. Humans need a <a href="https://doi.org/10.1038/nature11550">diverse microbiome</a> with a variety of bacterial species that can quickly adapt to the wide range of foods that we might want to consume while still performing all those important functions like preventing inflammation. So what are some things that you can do to support a healthy, diverse microbiome?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/308201/original/file-20191223-11914-1a88384.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308201/original/file-20191223-11914-1a88384.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308201/original/file-20191223-11914-1a88384.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=368&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308201/original/file-20191223-11914-1a88384.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=368&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308201/original/file-20191223-11914-1a88384.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=368&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308201/original/file-20191223-11914-1a88384.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=463&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308201/original/file-20191223-11914-1a88384.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=463&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308201/original/file-20191223-11914-1a88384.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=463&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Antibiotics or the wrong diet damage the good bacteria living in the gut and promote the growth of harmful bacteria.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/antibiotics-wrong-diet-damage-good-bacteria-1390060613">Soleil Nordic/Shutterstock.com</a></span>
</figcaption>
</figure>
<h2>Eat your fruits and veggies</h2>
<p>While all the different foods that make up your <a href="https://doi.org/10.1038/nature12820">diet can influence the gut microbiome</a>, it is the fiber – the carbohydrates in our diet that we cannot break down ourselves but the bacteria in our gut can use readily – that drives the formation of a healthy microbiome. Eating a diverse and abundant selection of fruits and veggies is a great way to feed some of the most health-promoting bacteria in our gut. </p>
<h2>Add resistant starch</h2>
<p>Most of the starch in our diet - like white bread and pasta - is quickly broken down and absorbed. But a fraction of that starch is resistant to digestion and acts more like a fiber, feeding the bacteria in our gut. <a href="https://doi.org/10.1016/j.copbio.2019.10.008">Resistant starch</a> has been identified as particularly beneficial for supporting all of those healthy functions of the gut microbiome. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/308216/original/file-20191223-11904-kuv2zn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308216/original/file-20191223-11904-kuv2zn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/308216/original/file-20191223-11904-kuv2zn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308216/original/file-20191223-11904-kuv2zn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308216/original/file-20191223-11904-kuv2zn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308216/original/file-20191223-11904-kuv2zn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308216/original/file-20191223-11904-kuv2zn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308216/original/file-20191223-11904-kuv2zn.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"></a>
<figcaption>
<span class="caption">Leftover macaroni, pasta and potato salads may be better for you microbes when they are a couple of days old.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/macaroni-salad-pasta-potato-containers-ready-94920760">Mark Skalny</a></span>
</figcaption>
</figure>
<p>Some sources of resistant starch include potatoes and legumes. All sources of starch can also become more resistant after <a href="https://doi.org/10.1111/1541-4337.12143">cooking and then cooling in the fridge</a>. So those leftover potatoes and pasta, cold or reheated, may have some added microbiome-promoting punch. </p>
<h2>Experiment with different fibers</h2>
<p>Not all gut microbiomes are the same and not all fibers are the same. Certain fibers and microbiomes will mix better than others, <a href="https://doi.org/10.1016/j.jmb.2016.06.021">depending on what functions are present</a>. This means that you need to do some experimentation to see what fibers will make you and your gut feel the best. You can do this with fiber supplements or with different categories of fiber sources such as whole grains, legumes or cruciferous vegetables like broccoli. Give your microbiome a couple of weeks to adjust to each fiber source to see how it responds. </p>
<h2>Exercise for both you and your microbes</h2>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/308215/original/file-20191223-11924-fgu0c7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308215/original/file-20191223-11924-fgu0c7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/308215/original/file-20191223-11924-fgu0c7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308215/original/file-20191223-11924-fgu0c7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308215/original/file-20191223-11924-fgu0c7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308215/original/file-20191223-11924-fgu0c7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308215/original/file-20191223-11924-fgu0c7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308215/original/file-20191223-11924-fgu0c7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Exercise is good for you microbes too.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/mature-man-exercising-362163422">pixelheadphoto digitalskillet/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>Regular physical activity is not only good for your heart, it is <a href="https://doi.org/10.1016/j.dld.2017.11.016">good for your gut, too</a>. <a href="http://doi.org/10.1038/s41591-019-0485-4">Studies recently showed</a> that some of the lactate produced during exercise can impact certain gut microbes – although we don’t yet know how and why. Start slow if you haven’t had regular physical activity as part of your daily life. If you start on New Year’s, by Valentine’s Day you could be walking daily, or doing some time of activity that you like, to help your heart, mind and gut. </p>
<h2>Add probiotic foods into your diet</h2>
<p>What are probiotic foods? These are foods that contain microorganisms that have a health benefit. There are several different kinds of helpful microorganisms that are added to foods like yogurt, or are naturally found in other fermented foods – like sauerkraut or kimchi – that give them a <a href="http://dx.doi.org/10.1093/nutrit/nuy056">health-promoting effect</a>. Give one of these foods a try in the new year. You might be wondering if probiotic supplements are as beneficial as probiotic food. So far there isn’t enough evidence to say that – so stick with food. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/308214/original/file-20191223-11904-py7gfz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308214/original/file-20191223-11904-py7gfz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308214/original/file-20191223-11904-py7gfz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308214/original/file-20191223-11904-py7gfz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308214/original/file-20191223-11904-py7gfz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308214/original/file-20191223-11904-py7gfz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308214/original/file-20191223-11904-py7gfz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308214/original/file-20191223-11904-py7gfz.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">These foods, which include fermented vegetables, contain beneficial microbes: kimchi, red beets, apple cider vinegar, coconut milk yogurt, cucumber pickles and sauerkraut.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/set-fermented-food-great-gut-health-781935256">marekuliasz/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>[ <em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=youresmart">You can read us daily by subscribing to our newsletter</a>. ]</p><img src="https://counter.theconversation.com/content/129215/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Connie Rogers receives funding from the American Institute for Cancer Research, US Department of Agriculture,McCormick Spice Institute. She is a member of the Nutrition Advisory Panel for the California Dried Plum Board. </span></em></p><p class="fine-print"><em><span>Darrell Cockburn receives funding from the American Heart Association, the US Department of Agriculture and the Pennsylvania Department of Agriculture. </span></em></p>For your 2020 New Year’s resolutions, think about keeping the microbes that live inside your gut healthy. Look after them and they’ll look after you.Connie Rogers, Associate Professor of Nutritional Sciences , Penn StateDarrell Cockburn, Assistant Professor of Food Science, Penn StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1161262019-06-21T12:14:03Z2019-06-21T12:14:03ZBacteria live on our eyeballs – and understanding their role could help treat common eye diseases<figure><img src="https://images.theconversation.com/files/280339/original/file-20190619-171271-1klbm8n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The eye has a collection of microbes living on the surface that keep it healthy. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/human-eye-medical-detail-1345654691?src=3EN65aoLrSklI70CS0rGYw-1-0&studio=1">photoJS/Shutterstock.com</a></span></figcaption></figure><p>You may be familiar with the idea that your gut and skin are home to a collection of microbes – fungi, bacteria and viruses – that are vital for keeping you healthy. But did you know that your eyes also host a unique menagerie of microbes? Together, they’re called the eye microbiome. When these microbes are out of balance – too many or too few of certain types – eye diseases may emerge. </p>
<p>With a study showing bacteria live on the surface of the eye and <a href="https://doi.org/10.1016/j.immuni.2017.06.014">stimulate protective immunity</a>, scientists are beginning to discover the microbial factors that can be exploited to create innovative therapies for a range of eye disorders like <a href="https://nei.nih.gov/health/dryeye/dryeye">Dry Eye Disease</a>, <a href="https://www.ninds.nih.gov/Disorders/All-Disorders/Sj%C3%B6grens-Syndrome-Information-Page">Sjogren’s Syndrome</a> and <a href="https://nei.nih.gov/health/cornealdisease/">corneal scarring</a>. One day it may be possible to engineer bacteria to treat eye diseases in humans. </p>
<p><a href="https://scholar.google.com/citations?view_op=search_authors&mauthors=Anthony+St.+Leger&hl=en&oi=ao">I’m an immunologist</a> studying how the eye prevents infection. I became interested in this field because humans get only two eyes, and understanding how bacteria affect immunity may be the key to avoiding up to 1 million visits to the doctor for eye infections and save <a href="https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6345a3.htm?s_cid=mm6345a3_w">US$174 million per year in the U.S. alone</a>. </p>
<h2>Eye microbiome</h2>
<p>When discussing the microbiome, most scientists usually think of the gut, and deservedly so; researchers think one colon can <a href="http://doi.org/10.1371/journal.pbio.1002533">harbor more than 10 trillion bacteria</a>. That being said, more attention is now being focused on the impact microbiomes have at other sites, including the <a href="https://doi.org/10.1038/nrmicro2537">skin</a>, and areas with very few bacteria, like the <a href="https://doi.org/10.4049/jimmunol.1600279">lungs</a>, <a href="https://doi.org/10.1146/annurev-micro-092611-150157">vagina</a> and <a href="https://www.aao.org/eye-health/anatomy/microbiome-of-eye">eyes</a>. </p>
<p>For the last decade, the role of the microbiome <a href="https://doi.org/10.1016/j.exer.2013.06.003">in ocular health was controversial</a>. Scientists believed that healthy eyes lacked an organized microbiome. Studies showed that bacteria from the air, hands or eyelid margins could be present on the eye; however, many believed these microbes were simply killed or washed away by the continual flow of tears. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/280340/original/file-20190619-171188-1gxxupd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/280340/original/file-20190619-171188-1gxxupd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/280340/original/file-20190619-171188-1gxxupd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/280340/original/file-20190619-171188-1gxxupd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/280340/original/file-20190619-171188-1gxxupd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/280340/original/file-20190619-171188-1gxxupd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/280340/original/file-20190619-171188-1gxxupd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/280340/original/file-20190619-171188-1gxxupd.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">Wearing contact lenses alters the eye microbiome.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/closeup-man-holding-transparent-contact-lens-1158955207?src=f2U_tCZrEbOxCzeCaCz0yQ-1-0&studio=1">Andrey_Popov/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>Only recently have scientists concluded that the eye does, indeed, harbor a “core” microbiome that appears dependent on <a href="http://doi.org/10.1167/tvst.7.6.16">age</a>, geographic region, ethnicity, <a href="http://doi.org/10.1128/mBio.00198-16">contact lens wear</a> and state of disease. The “core” is limited to four genera of bacteria <em>Staphylococci</em>, <em>Diphtheroids</em>, <em>Propionibacteria</em> and <em>Streptococci</em>. <a href="http://doi.org/10.1167/iovs.16-19803">In addition to these bacteria, torque teno virus</a>, implicated in some intraocular diseases, also counts as a member of the core microbiome as it is present on the surface of the eye of 65% of healthy individuals. </p>
<p>This suggests that doctors should think more deeply about the risks and benefits to the microbiome when prescribing antibiotics. The antibiotics may kill bacteria that are providing a benefit to the eye.</p>
<p>In a recent study spanning more than a decade and including more than over 340,000 patients in the U.S., the authors found that <a href="http://doi.org/10.1016/j.ophtha.2017.04.034">antibiotics were used to treat 60% of acute conjunctivitis</a> (pink eye) cases. But viral infections are the most likely causes of pink eye, and not treatable with antibiotics. More striking, even cases caused by bacteria often <a href="http://doi.org/10.1016/j.ophtha.2017.04.034">resolve in 7-10 days without intervention</a>. It is well known that excessive or inappropriate antibiotic use can disrupt the microbiome, leading to <a href="http://doi.org/10.1016/j.cell.2014.03.011">infection</a>, <a href="https://doi.org/10.1016/j.intimp.2018.10.021">autoimmunity</a> and even <a href="https://doi.org/10.1002/eji.201444972">cancer</a>.</p>
<h2>Discovering an eye-colonizing microbe</h2>
<p>Within the past decade, studies assessing the eye microbiome and disease have boomed. They’ve generated an immense amount of data, but most of it is correlative. This means that certain bacteria have been linked to certain diseases, like <a href="http://doi.org/10.1038/srep23561">Sjogren’s Syndrome</a> or <a href="https://doi.org/10.1371/journal.ppat.1005855">bacterial keratitis</a>. However, whether these bacteria are causing these diseases is still unknown. </p>
<p>During my time at the <a href="https://nei.nih.gov">National Eye Institute</a>, I used mice to identify whether bacteria at the surface of the eye could stimulate an immune response to protect the eye from blinding pathogens like the bacterium <em>Pseudomonas aeuruginosa</em>. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/280465/original/file-20190620-149843-6tdx9u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/280465/original/file-20190620-149843-6tdx9u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/280465/original/file-20190620-149843-6tdx9u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/280465/original/file-20190620-149843-6tdx9u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/280465/original/file-20190620-149843-6tdx9u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/280465/original/file-20190620-149843-6tdx9u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/280465/original/file-20190620-149843-6tdx9u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/280465/original/file-20190620-149843-6tdx9u.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"><em>C. mast</em> bacteria (green) living on the surface of a mouse eye.</span>
<span class="attribution"><span class="source">Tony St. Leger</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>In 2016, ocular immunologist <a href="https://irp.nih.gov/pi/rachel-caspi">Rachel Caspi</a> at the National Eye Institute and I hypothesized that protective bacteria were living near or on the eye. Indeed, we found a resident bacterium, <em>Corynebacterium mastitidis</em> (<em>C. mast</em>), that stimulates immune cells to produce and release antimicrobial factors that kill harmful microbes into the tears. </p>
<p>Through a series of experiments, <a href="https://nei.nih.gov/intramural/imm-reg#aboutourwork">the Caspi lab</a> was able to <a href="https://doi.org/10.1016/j.immuni.2017.06.014">show for the first time a causal relationship</a> between <em>C. mast</em> and a protective immune response. Whenever <em>C. mast</em> was present on the eye surface, mice were more resistant to two species of bacteria known to cause blindness: <a href="https://doi.org/10.1016/j.immuni.2017.06.014"><em>Candida albicans</em> and <em>Pseudomonas aeuruginosa</em></a>. </p>
<p>Now, <a href="http://ophthalmology.pitt.edu/people/anthony-st-leger-phd">in my lab</a>, we would like to exploit this relationship between <em>C. mast</em> and ocular immunity to develop novel therapies to prevent infection and possibly target more widespread diseases like Dry Eye Disease. </p>
<h2>Engineering microbes to improve eye health</h2>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/280342/original/file-20190619-171200-km3uwn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/280342/original/file-20190619-171200-km3uwn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/280342/original/file-20190619-171200-km3uwn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/280342/original/file-20190619-171200-km3uwn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/280342/original/file-20190619-171200-km3uwn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/280342/original/file-20190619-171200-km3uwn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/280342/original/file-20190619-171200-km3uwn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/280342/original/file-20190619-171200-km3uwn.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">Future therapies to treat dry eye disease may contain microbes engineered to live on the eye and supply therapeutic chemicals.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/conjunctivitis-redness-inflammation-eye-vessels-drops-725446807?src=PyhVGh42YKM1-4m3znN5Og-1-18&studio=1">Timonina/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>The first step toward developing such therapies is figuring out how bacteria colonize the eye. For this, my lab is collaborating with the <a href="http://ophthalmology.pitt.edu/research/research-laboratories/charles-t-campbell-microbiology-laboratory">Campbell Laboratory</a> at the University of Pittsburgh, which houses one of the most extensive collections of human ocular bacteria in the country. With our unique experimental setup with mice and advanced genetic analyses, we can use this microbial library to begin to identify specific factors required for the microbes to colonize the surface of the eye.</p>
<p>Then, with ophthalmologists and optometrists in the <a href="https://www.upmc.com/services/eye">UPMC Eye Center</a>, we are beginning to analyze the immune signatures within the eyes of healthy and diseased patients. Here, our hope is to use this technology as a new diagnostic tool to target the microbes causing disease rather than immediately treating infections with broad spectrum antibiotics that kill the good microbes too. </p>
<p>Finally, one of our loftier goals is to genetically engineer eye-colonizing bacteria to act as long-term delivery vehicles to the surface of the eye. In the gut, genetically modified bacteria have been shown to <a href="https://doi.org/10.1126/science.289.5483.1352">alleviate diseases like colitis</a>. </p>
<p>We hope that this new “prob-eye-otic” therapy would act to secrete immune regulating factors, which would limit symptoms associated with conditions like <a href="https://nei.nih.gov/health/dryeye/dryeye">Dry Eye Disease</a>, which affects around <a href="https://doi.org/10.2147/opth.s5555">4 million people in the U.S.</a> per year. </p>
<p>In this developing field, there is still much to learn before physicians can begin manipulating the ocular microbiome to fight disease. But one day perhaps rather than just squirting eye drops into your dry eyes, you’ll squirt in a solution with some bacteria that will colonize your eye and secrete the lubricants and other factors your body is missing. Stay tuned.</p><img src="https://counter.theconversation.com/content/116126/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tony St. Leger receives funding from the National Institutes of Health and The University of Pittsburgh. </span></em></p>Just like the gut, the skin and the mouth, the eye also has a collection of microbes that keep it healthy. Understanding the eye microbiome may lead to new probiotic therapies.Tony St. Leger, Assistant Professor of Ophthalmology and Immunology, University of PittsburghLicensed as Creative Commons – attribution, no derivatives.