What is the skin microbiome?
If you want a comprehensive overview of daily skincare, start with our science-based skincare routine guide. In this article, we'll focus on the skin microbiome: what it is, how skin and microorganisms interact, and which cosmetic claims can be considered justified based on current knowledge.
The skin microbiome includes the microorganisms living on the skin, their genetic material, and their interaction with the skin's environment. Its composition varies between individuals and body regions, and the main features of the microbiome can remain quite stable for years in the same person. Cosmetics can alter the chemical and microbial environment of the skin, but the claim that a product "balances" the microbiome requires relevant studies on the specific finished product (Grice et al., 2009; Oh et al., 2014, 2016).
What is the difference between skin microbiota and microbiome?
Bacteria, fungi, viruses, and other microorganisms live on the skin surface, in hair follicles, and around sebaceous glands. The community of these organisms is called the skin microbiota.
The skin microbiome is a broader term. It includes microorganisms, their genes, metabolites, and their interaction with the surrounding environment. In everyday cosmetic language, the terms microbiota and microbiome are often used synonymously, but scientifically, they do not mean exactly the same thing.
The microbial composition of the skin is not uniform across the entire body. Oily, moist, and dry areas offer different living conditions for microorganisms. For example, the microbiota of the forehead, armpit, forearm, and foot can differ significantly from each other. Differences between individuals are also large, and studies have shown that a person's skin microbial profile can maintain individual characteristics over a long period (Grice et al., 2009; Oh et al., 2014, 2016).
From this, an important practical principle follows: in science, there is no single universal "ideal skin microbiome" composition that all people should strive for. Also, greater microbial diversity does not automatically mean healthier skin in every body region and every situation. Results must be interpreted in conjunction with the body region, skin condition, age of the person, and the research method used. This is a reasoned conclusion based on existing studies, not a cosmetic diagnosis that can be determined by a simple test.
How do skin and microorganisms interact?
The skin is not just a passive surface for microorganisms. Skin oil secretion, moisture, temperature, pH, hair follicles, and the state of the protective barrier all influence which microorganisms persist in a particular area.
The effect also works in the opposite direction. Skin microorganisms compete for living space and nutrients, produce metabolites, and interact with skin cells and the immune system. Therefore, it is inaccurate to simply divide microorganisms into "good" and "bad." The same species can behave differently depending on the strain, quantity, location, and skin condition (Byrd et al., 2018).
In acne research, for example, it has been found that the mere presence of Cutibacterium acnes may not be crucial, as this bacterium is often found on healthy skin. Differences have been observed in the distribution of specific bacterial strains and their genetic characteristics between people with and without acne (Fitz-Gibbon et al., 2013).