Dear Doctor: I heard two teenagers in line at the drug store talking about the skin microbiome and how you shouldn’t use soap on your face because it wipes out the good bacteria. We hear a lot about the gut microbiome lately, but is the skin microbiome really even a thing?
Dear Reader: The word “microbiome” refers to any community of microorganisms that live together peaceably in a specific environment. To reflect the fact that they don’t cause illness, it’s said that they “colonize” an area rather than “infect” it.
In terms of the human microbiome, we’re talking about the vast array of microbes that live upon and within our bodies. These colonies are typically composed of bacteria, bacteriophages, fungi, protozoa and viruses. Depending on their location, they number into the millions, billions and, in the gut microbiome, trillions.
In addition to the gut, anatomical sites of distinct microbiomes in and on the human body include the nose, mouth, esophagus, lungs, genitals and even the hidden depths of the belly button. And, yes, the skin, which is often referred to as the largest organ in the body, is the site of a microbiome. Multiple ones, in fact. They differ depending on their specific locations, and are affected by the variety of environments they interact with, including oily, moist and dry.
For instance, the skin between your toes, which spends long stretches of time in the moist darkness created by socks, shoes and perspiration, hosts a different profile of microbes than does the skin on your scalp, behind your ears or on the backs of your hands.