Skin microbiome claims: sticking with the second-best cosmetic claims while science, technology and the regulatory landscape matures

It is only recently that we have started to understand the key role played by the microbiome that exists on our skin, a complex ecosystem of bacteria, fungi and viruses that populates our largest organ. The idea that the health of our skin is tied to the balance that these microorganisms have between them is ground-breaking and changes the whole landscape surrounding the skincare world. Conventional skincare wisdom and personal hygiene habits of the past several decades have always treated microbial growth as a bad thing, giving rise to powerful detergents and even anti-microbial ingredients in order to clean the skin. However, using strong cleansers and other cleansing agents disrupts the balance between the skin and the microbiome, often leading to dermatitis and other skin reactions. In light of the discovery of the essential role that the microbiome plays in skin health, we need to reconsider our skincare habits, to make sure that they are not harmful to this balance.

One of the best things one can do to maintain a healthy microbiome is to disturb it as little as possible, as it is a self-balancing ecosystem. When in its balanced state, the microbiome is our best ally in maintaining the health of our skin. Consequently, both consumers and brands are focused on identifying the key aspects of this new area of microbiome-gentle products. Consumers are becoming more selective and knowledgeable, and brands are on the lookout to convey this fresh concept.

Even as the trend for microbiome-friendly skincare gains momentum, there are some concerns regarding the scientific basis for claims of efficacy. In our view, the first wave of products that made such claims were by mere association of terms. Companies used ‘hero’ ingredients, typically ingredients known from the food industry that were already thought to be pre-, pro-, or postbiotics, and claimed microbiome-related benefits that were lacking scientific evidence to back the claim of a microbiome-supporting effect when applied to the skin. Since then, some forward-thinking companies have generated promising data on the use of extracts of microbial cultures and specific microbial strains, and their effects on skin barrier and hydration. Testing is now available, and we can finally rely on claims that are rooted in hard science.

In spite of the huge leaps that have been achieved, the field of microbiome science is still in its infancy and its complexity is not fully understood. Strong, breakthrough claims such as ‘’improving’’, ‘’balancing’’ or ‘’nourishing’’ require a high level of scientific evidence. Regulatory authorities have reaffirmed this when examining such cases. There is a thin line that separates cosmetic products from pharmaceutical ones. By definition (EC1223/2009), a cosmetic product is one that has functions like “cleaning, perfuming, protecting, or keeping the body in good condition.’’ Therefore, claims of supporting or enhancing the health of the microbiome could potentially be viewed as falling outside the scope of what is allowable in claims for cosmetic products. The reason for such a determination is that the skin microbiome could be deemed to be a part of the body, and thus such a claim would imply a physiological effect which would make the product a pharmaceutical one. Consequently, a thoughtful review must be undertaken when making claims about the effect that a product may have on the microbiome. We believe that the term ‘’skin microbiome gentle’’ is currently the most accurate and descriptive term that is allowable for cosmetic products, as it means a product that does not interfere with the balance of a healthy microbiome.

Although “microbiome-gentle” products should be the goal, it is not a given for cosmetics products. The use of preservative systems in cosmetics is necessary to kill contaminating microorganisms but those preservatives can also disrupt the microbiome ecosystem on the skin. Cosmetic preservatives are not the only ingredients that can disrupt the microbiome. Surfactants, essential oils, ingredients that affect the pH level, and other coformulants, can have a synergistic effect which may be damaging. Given the importance of the microbiome to skin health, microbiome gentleness can and should be considered a new standard that cosmetic products should adhere to and testing the whole formula is a must.

At the moment, there is little regulatory guidance on the standards and tests that should be conducted in order to determine which ingredients have an effect on the microbiome. Consequently, brands must rely on experts in microbiology and dermatology. There is an open discussion regarding which testing methods are better suited for determining the effect of cosmetic ingredients on the skin microbiome. The two main methods are in vivo and in vitro testing. In vivo testing is conducted on volunteers who apply the products to be studied on their skin and their skin microbiome is analysed before and after use with 16sRNA sequencing technology. While an in vivo study can offer a vast amount of information, it requires complex statistical analysis and suffers from variations in the microbiome from one volunteer to the next. The cost of entry in using such technology is huge and hence its widespread adoption seems unlikely in the near future. In vitro studies are conducted on a panel of microorganisms that is deemed to be representative of the average healthy microbiome of humans as it contains the majority of the species present on the skin. The results are highly reproducible and can ascertain to the microbiome gentleness of the ingredient or product. The cost of in vitro testing is such that it can be quickly and easily deployed in order to determine benchmarks for microbiome gentleness across the industry.

In conclusion, due to a lack of regulatory guidance and the low level of maturity around microbiome technology and science, in vitro testing of cosmetic ingredients and final products is the most suitable testing method at this point in time. In vitro-based protocols may be used to obtain evidence to support the claim “skin microbiome gentle”. Formulations and ingredients tested in vitro through validated protocols, would not interfere with the healthy skin microbiome.

Kind to Biome offers validated in vitro testing according to the highest scientific standards. By employing different panels of microbes to represent the unique microbiomes found on areas of the body (face, scalp, body, intimate area, baby’s skin and others), we can measure the influence that a product has on a given microbiome and make an accurate assessment of how the product would affect the microbiome once applied to the skin. Upon analysis, if a product does not appear to affect the microbial strains that it is applied to, then the product can be considered to be skin microbiome gentle.

By Leo Salvi. This article is the opinion of the author and reflects the author's views.

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