Your skin has its own microbiome, which, like the gut microbiome, trains and supports local immune function and keeps bad bacteria at bay. There is much less known about the skin microbiome, but this rapidly emerging cosmetic medicine field will change how we treat our skin and challenge what we thought we knew. It is understood that skin health and barrier function, though primarily our skin microbiome’s responsibility, is impacted and controlled by our gut microbiome. When in balance, the good organisms that live on our skin obtain nutrients from cell debris and sebum and produce products that help us defend against potential pathogens (plus many other functions).
The skin microbiome varies across your body.
The skin presents a very different environment from the gut; it is acidic (sour), salty from sweat, the surface is largely dry (except in the folds). It presents diverse surfaces, from areas coated in an oil-rich sebaceous material, inside the oil-rich hair follicles or arid foot environments. The skin microbiome varieties vary across the body, depending on the microenvironment. (feet have an entirely different microbiome that your armpits!) But all of the skin’s outside surface is very different from the neutral, moist, food-rich environment of the gut, which houses many more times the number of microbes than the skin surface. However, there are around 1000 species of bacteria living on your skin, as well as a range of other species like virus, fungi, archaea and even mites!
Our skin microbiome helps build our immune system.
Certain bacteria which arrive at birth train our immune system to accept good bacteria and reject bad bacteria, and so our skin bugs are significant for stopping infection. As we progress through life, the skin microbes continue to change and diversify until puberty. So the good bacteria help communicate with our skin cells and immune cells, helping the skin barrier function and settling inflammation. It is a two-way street. A healthy barrier also supports good bacteria such as Staph epidermis, which produce antimicrobial antibodies to kill harmful bacteria and keep Staph aureus at bay. It is a win-win for us and our resident bugs!
The skin microbiome – healthy biome – happy skin
Maintaining the balance and function of the skin ecology is much more complex, though, and as with the gut, it is the balance of the bacteria that is important. So a species can live on the skin and not cause harm. If it overgrows or becomes dominant, it can indeed cause damage – as occurs in acne, rosacea, eczema and dandruff. When our resident bugs are in balance, our skin barrier is intact and healthy, our skin is happy.
Nature 588, S209 (2020)