“To see a world in a grain of sand, and a heaven in a wild flower.”

Auguries of Innocence, William Blake

If I were to ask you to think of the worlds most amazing ecosystems, what would come to mind?  You’d probably think big, perhaps the Serengeti in Africa with its herds of animals constantly playing out the high stakes game of predator and prey.  Perhaps your mind would wander to the Great Barrier Reef, stretching for nearly 2000 miles off the east coast of Australia, where more than 1500 of species of fish live in the unique habitat it provides.  For me it would be the island of Tasmania, where its wonderful and charismatic animals such as Wombats, Echidnas, Tasmanian Devils and Platypus, roam across pristine wilderness.

Shrinking the scale a little, how about a smaller ecosystem?  Over the years I’ve turned the garden behind our house into a wildlife garden.  I planted native flowers and shrubs, I don’t use pesticides and weedkillers, I leave log and leaf piles in places around it to provide habitat for insects and animals to live, and I have different layers of habitat from close to the ground to a couple of tall trees.  The insects feed on the flowers, the birds feed on the insects.  Hedgehogs visit at night, keeping the slugs down.  There is life and death in the garden and the habitat it provides supports what lives there. But also, the life present there supports the habitat.  Worms burrow through the soil, breaking it up, and helping drainage and making it easier for the plants to take root.  Low growing plants cover the ground and prevent it from losing too much water when the sun hits it and keeping it moist.  The birds eat in the garden, but they also defecate there, adding nutrients back to the soil, replenishing those lost to the growing plants.  Fungi and mushrooms grow on the log piles, breaking down the tough cellulose fibers.  We have an ecosystem that works as a complex and balletic collection of interlocking cycles of growth and decay, life and death.

Now, shrink the scale again.  What if I were to say to you, that the surface of your skin is a complex ecosystem, with the richness and diversity of a rainforest, and in which the health of what is living on and in your skin, is as vital to your own health as the structure of the skin itself?  Those of us who work on skin learn early on how it is created. Starting in the viable epidermis, where the cells that will eventually make up the Stratum Corneum are born.  These cells are pushed upwards, where they differentiate and die, flattening out and creating the outer layer of the skin, that we see and interact with.  These are the dead squames of keratin that form the surface of your skin.  How often have you heard that?  But to consider the Stratum Corneum as a layer of dead cells, is like thinking of the Great Barrier Reef just as 2000 miles of pretty calcium carbonate structures under water. It’s missing the point, and in fact is about as wide of the mark as it can be. 

The Stratum Corneum is homes to thousands of species of bacteria and fungi, each adapted to live in a particular environment.  Some like the warm moist rainforest areas of your armpits, others love to roam on the wide open planes of your cheek and forehead.  Surely though they are bad for you and there is little good to be had from them?  Well, surprisingly, without them we really would be in trouble. Big trouble. Some bacteria by their very presence, keep bad bacteria numbers low, and prevent them from becoming established and causing problems.  Bacteria excrete acidic material, which helps to reduce the pH of the skin, and provide the correct acidity range for enzymes to work to keep the skin healthy and desquamating properly, shedding the outermost corneocytes and preventing the build up of dry skin flakes. Without this acid mantle the skin cannot function properly, and the end result is that the balanced ecosystem breaks down. It should be no surprise that atopic skin has elevated pH, and a markedly different bacterial population to healthy skin.

Like all great ecosystems though, our skin is only there because of a delicate set of interlocking cycles. When these become disturbed or disrupted, it is then that we start to see problems.  Back to the global scale, it’s impossible to ignore what is going on around us on our little planet. Warming temperatures make the sea water absorb more carbon dioxide and become more acidic.  Warming water kills the coral and increased acidity promotes the dissolution of the calcium carbonate it produces. Destroying a rainforest and creating a monoculture in its place for farming, eradicates the wildlife there and creates a relatively sterile environment.  Removing trees from the side of a hill, either for farming or building, means that when it rains heavily, there is nothing to stabilise the soil and it all washes away, removing what little soil there was.

On our skin, with our everyday lives we do our best to put it through an extinction level event on a regular basis.  We wash, often many times a day, using soaps and cleansers, thinking that bacteria are a huge problem. All this does is remove great swathes of what was growing there, leaving a blank canvas for the most aggressively growing and opportunistic species to grow back if kept unchecked.  We bake in the sun to feel better or to give ourselves a pleasing appearance, damaging the skin and exposing the surface ecosystem to high levels of UV.  We often spend time in offices with air conditioning and low humidity, which can be very different to the outside conditions.  This rapidly changes the humidity the skin is exposed to multiple times a day, and drying it out.  Those of us who live in or near cities expose it to pollution, and just like the pollution problems globally which have a huge impact on the ecosystem, this exposure can impact correct skin function.

Even for me, a ‘to the core’ pessimist, this sounds awful.  Too much doom and gloom.  But is it all doom and gloom, or can we take what we have learned from how global ecosystems operate, to help us understand and better communicate how our skin works and how we can work with it?  Nature is about balance – enough but not too much – and with balance comes stability.  Altering the balance of predators and prey can lead to population collapse – too few prey and the predators die out.  Once the predators die out, the prey population booms until there is not enough food for them all and they die off.  The populations eventually settle at stable levels, where both predator and prey can be sustained. Aggressive cleansing and indiscriminate use of antimicrobials will kill bacterial populations, and alter the ratios of each species present.  This can tip the balance in favour of bad bacteria on the skin which would normally be kept in check by having a wide variety of species present.  It is well know that in atopic skin, there is a lower diversity in the microbiome than in healthy skin.  Be careful how you cleanse….. 

Water is required for plants to grow – too little and the ground dries and cracks, which when combined with high winds can lead to continent size dust clouds and loss of the very soil itself.  Too much and the ground floods, drowning everything there, or soil is washed away.  At the right water levels though, life can grow and flourish.  Skin is just the same.  Water is required to keep the skin flexible and to help modulate enzymatic activity.  Too much water and the skin becomes weak, and natural moisturising factors are washed out.  Too little water and skin dries and cracks, leaving the deeper layers open bacterial infection as the barrier is destroyed.  Balance, as with many things is the key – enough but not too much.

How about sunlight (and more importantly UV) exposure?  Too much and we burn, too little and we cannot make Vitamin D.  On a planetary scale we have our global sunscreen to help protect us – the ozone layer.  When that fails more UV reaches the surface of the Earth, and we have seen the effects of that on skin cancer rates especially in and around Australia.  Our own melanin acts in a similar way, reducing UV exposure, but often that is not enough especially for those that like to spend more time put in the sun.  We can apply topical sunscreens to boost our natural protection and help reduce UV exposure, but must ensure that we don’t block everything otherwise we cannot make out Vitamin D.  Again, balance.

When we look at our skin, to view it as just a layer of dead cells makes a much sense as looking at the Serengeti as a large field of soil or the Great Barrier Reef as a large calcium carbonate formation.  It is the life that flourishes in these ecosystems, that interacts and evolves with it, that make them the special places they are, and are intimately linked with how these systems grow and evolve.  Just because we tend not to be able to see the life which grows and thrives on our skin, doesn’t mean it isn’t there or that it isn’t vital to how our skin works. As Blake mused, “To see a world in a grain of sand, and a heaven in a wild flower”.  It really is less of a Stratum Corneum and more of a Stratum Ecologica.

A discussion of the importance of viewing the skin as an ecosystem based on my letter to the International Journal of Cosmetic Science, here .