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The skin safari: looking back on a decade of skin microbiome discoveries

Ahead of the Microbiome and Probiotics R&D and Business Collaboration Forum, Dr Monty Lyman takes us on a journey through the last decade of ground-breaking skin microbiome research, and peers ahead into the next.

When you look closely at the back of your hand, it is as if you are in a passenger aircraft peering down at the world from 30,000 feet. You see ridges and canyons made of marks, scars and tendons, all dwarfed by a great mountain range of knuckles. Maybe you can make out blue rivers of veins and, if you’re hairy, a forest encroaching from the arm. Just as from a plane, you can make out the terrain down below but there is no indication of any life. But when an aircraft starts to descend, you begin to detect buildings and roads, then individual cars moving along these roads. Finally, on landing and after leaving the airport, you see throngs of people on the streets, all of whom had been invisible to you from the window of the plane.

If it were possible to zoom in on the terrain of our skin in a similar way, you would enter a strange, exciting world containing diverse populations of microorganisms. Indeed, on the two square metres of our skin there are more than 1,000 different species of bacterium, not to mention fungi, viruses and mites. This diverse community includes commensal, mutualistic and pathogenic organisms, and over the past decade – particularly since the first findings of the Human Microbiome Project were released in the first years of the 2010s – we have made huge leaps in our understanding of this complex and fascinating world. Manipulating and adjusting these microbial populations has the potential to revolutionise dermatology and skincare. 

Skin microbiome research in the 2010s has unearthed as many curiosities as it has cures and as many questions as it has answers. One of the most complex (and divisive) has been that of the skin microbiome at the beginning of life. There is evidence that even the way in which we are born, whether vaginally or by caesarean section, could determine our future skin and gut microbiomes. When we first enter the world, as a greasy, squealing baby, our skin is largely a blank canvas that is ripe for colonization and immediately some of the microbes living in either the mother’s vagina or the skin around the C-section incision, as well as those in the hospital environment, will decide to make their home on the newborn baby’s surface. Exactly which types of pioneer species land on an infant’s skin could have long-term health consequences. In theory, vaginal microbes contain more appropriate microbes for immune system programming than the mother’s abdominal skin and those of the hospital environment, which some argue is why C-section babies appear to have an increased risk of developing allergies later on in life. So should we start swabbing all newborn babies with their mother’s vaginal mucus, known as ‘vaginal seeding’? While this an exciting area of research, there currently isn’t enough long-term evidence to make informed clinical decisions, and in 2017 The American College of Obstetricians and Gynecologists wisely advised against vaginal seeding outside of research studies until we have enough data.

Manipulating and transplanting microbes to tackle skin disease – in a similar way to the more established route of prebiotics and probiotics in gut health – shows significant promise. Vitreoscilla filiformis bacteria – tiny, transparent organisms found in the waters of natural spas – have been shown to communicate to our skin’s immune system through a series of signalling pathways, which in turn produces more regulatory T cells, dampening down the immune response and helping to alleviate eczema. Right now we still largely rely on steroid creams to dull the immune response of eczema; creams containing bacteria such as V. filiformis could soon provide a sustainable, side-effect free, alternative. This decade has also revealed how larger organisms on the skin contribute to disease. The house dust mite is a significant aggravating factor in eczema and skin irritation, and researchers at the laboratory I worked in at the University of Oxford discovered that this is due to a substance these mites produce, called phospholipase, which breaks down fat molecules in the skin that consequently stimulates the immune system. 

Recent microbiome research may even find a cure for body odour. At the 2017 Karolinska Dermatology Symposium in Stockholm, Sweden, the attendants were introduced to the results of a world-first: an underarm bacteria transplant. For his experiment, Dr Chris Callewaert of the University of California San Diego found a pair of identical twins, one of whom didn’t seem to smell at all while the other had particularly strong body odour. He asked the odourless twin not to wash for four days so that he could cultivate a good quantity of whatever species of sweet-smelling bacteria he possessed, whilst the other had to scrub his armpits each day for the four days to prepare his skin for the new population of microbes. The dead skin of the first twin was scraped off and swabbed into the armpits of his smelly double. Remarkably, the smelly twin’s odour disappeared and the effects lasted for a year. Although these are still early days, the promising results were repeated in sixteen out of eighteen further pairs. Perhaps we will soon be ditching deodorant in favour of donations from unscented friends.

At first glance, our skin looks like a bare, inhospitable landscape. It’s clear, however, that our body is covered in habitats filled with wildlife worthy of a nature documentary. Our skin is their world. The past decade has seen a revolution in our understanding of how the skin’s microbiome influences skin disease, and it is this is only going to deepen over the next decade in areas such as metagenomics, phage therapy and computational bioinformatics to name just a few. It will hopefully also be the decade in which this research is translated into evidenced-based clinical products. 

Monty Lyman is a British doctor and author. His debut book is The Remarkable Life of the Skin, published by Transworld, Penguin Random House (UK) and Grove Atlantic (USA). It was a Sunday Times ‘Must Read’, one of their ‘Best Books of 2019’, chosen as a BBC Radio 4 Book of the Week and was shortlisted for the Royal Society Science Book Prize.

Learn about the latest discoveries and novel R&D trends from world-leading microbiome and probiotic researchers at the Microbiome and Probiotics R&D and Business Collaboration Forum. View the programme.

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