The microbiome’s role within the digestive system has long been known, but that of the skin’s microbiome is a comparatively recent concept. The earliest reference found is an article called ‘Microbial Ecology of the Skin’, published in 1988, that describes the symbiotic relationship between human skin and microorganisms.
Ever ready to exploit any possible marketing benefits, the cosmetic industry seized on the idea of protecting it or feeding it with probiotics. Probiotics are defined by the World Health Organization as live microorganisms that, when administrated in adequate amounts, confer a health benefit to the host.
There is a major problem in that cosmetic regulations limit the presence of microorganisms to less than 1,000cfu/g within a product.
The microbiome is the collective genomes of the bacteria, bacteriophage, fungi, protozoa and viruses that live inside and on the human body.
The microbiota are the microorganisms found in a specific environment by type. A healthy skin microbiome is a balance of many different organisms, which varies from person to person and across the different areas of the body of each person.
There is a natural equilibrium between beneficial commensal organisms and detrimental pathogenic strains of bacteria, fungi and yeasts. The presence of commensal bacteria protects against pathogenic bacteria via two mechanisms. They compete for nutrients and space, which reduces the risk that pathogenic bacteria will proliferate.
They may also produce bacteriocins that can kill other bacterial species.
Cosmetics may have a deleterious effect as the presence of preservatives may upset this equilibrium, allowing colonisation by pathogenic organisms.
The Covid-19 pandemic exacerbated this problem as people were encouraged to wash their hands at frequent intervals, and to use sanitising gels and sprays at every opportunity.
There were many references to the skin’s microbiome by presenters of cosmetic ingredients at in-cosmetics Global 2022 and all agreed that it comprised up to a million microbes per square centimetre and that diversity was essential for a healthy skin.
If this balance is disturbed it is termed dysbiosis and it can lead to acne, eczema, dry skin, psoriasis, dandruff, alopecia, skin allergies and asthma. Not only preservatives but essential oils, surfactants, alcohol or fragrances may also cause dysbiosis.
Kristin Neumann of MyMicrobiome gave an interesting presentation on the subject and said that current research on the skin microbiome clearly reveals that the best a cosmetic can do is not to have any adverse effect on the microbial balance of the skin.
Cosmetics that claim to restore, nourish, balance, or support the microbiome are misleading and the only claims that are scientifically valid are those like ‘respects’ and ‘does no harm to a healthy microbiome’.
Hence the theme of this article is ‘microbiome friendly cosmetic ingredients’ and I will discuss those ingredients that do not upset the diversity and numbers on key body sites; it will also include ingredients that are claimed to have a beneficial effect if supported by clinical evidence.