The Association of the Skin Microbiota With Health, Immunity, and Disease
The human skin represents one of the largest and most versatile organs of the human body. It functions as a protective interface between the largely sterile interior of the human body and the unsterile outer environment. Like other epithelial interfaces with the external environment, the human skin is densely colonized with a complex microbial community.1 The entire microbial community of a given habitat is also referred to as “microbiota” or “microbiome.” While “microbiota” rather refers to the microbial taxa associated with a given environment, a “microbiome” comprises the catalog of these microbes and their genetic material (DNA/RNA). However, both terms are often used interchangeably.2 For the sake of consistency, and because we largely focus on the interactions of different microbial taxa with the human host, we use “microbiota” throughout this text. “Microflora” is another widely used term for “microbial community,” particularly in medical circles. However, it originates from a time when microbiology was a subdiscipline of botany, and microorganisms were categorized as a kind of plant. Therefore, we suggest avoiding this term.
For a long time, this skin microbiota was seen as a source of contamination and infection. However, the human microbiome project and concomitant molecular, i.e., cultivation‐independent, research projects strongly suggested that the human skin microbiota is of major importance for human health and well‐being.