SKIN MICROBIOME
Skin microbiota and claims substantiation
Anne Charpentier – Skinobs, France
The evaluation of the effect of dermocosmetics or active products on the skin microbiota is evolving into more and more complex models. And yet, these never reach the sophistication of the ecosystem of the bacterial biofilm of the skin. In addition, it is now known that the skin microbiome is subject to intra-individual variations depending on the body areas and inter-individual according to genetic, intrinsic, and environmental factors.
A complex ecosystem deeply linked to the skin homeostasis Healthy skin promotes a skilled balance of the different bacteria present and vice-versa, skin homeostasis involves a diverse and highly controlled microbiome. Sometimes the simple decrease of one species can benefit others, which then become potentially pathogenic. 2D or 3D models including the inoculation of one or more microorganisms, living or inactivated, allow progression on specific problems, such as those associated with dysbiosis such as acne, atopic dermatitis, psoriasis, or scalp disorders. These approaches, which can sometimes be considered “reductionist” as the bacterial ecosystem of the skin is complex, remain unavoidable and contribute to the advancement of knowledge in the fields of skin biology and microbiology. Cosmetics should preserve the bacterial balance of healthy skin as varied as it may be and allow fragile and injured skin to regain a natural biofilm. Since the discovery of the intestinal
microbiota, the question of the skin microbiota (micro-organisms, bacteria, viruses, fungi, yeasts), is on everyone’s lips. 100 trillion bacteria are living in our bodies and everybody wants to know more about the impact of the cosmetics use on the skin bacteria ecosystem and how these phenomena can be measured? The microflora is usually subdivided in 2
groups: ■ Transient flora, saprophytic and pathogens microorganisms with Staphylococcus, aureus, Escherichia coli, Pseudomonas aeruginosa and Bacillus species… ■ Resident flora, pathogenic and commensal microorganisms with Proteobacteria, epidermidis, S. hominis Propionibacterium, Corynebacterium, Dermabacter, Brevibacterium, Micrococcus, P. aeruginosa, Pityrosporum, Malassezia, Demodex… The balance of cutaneous microflora (500 bacteria species) is dependent on several
www.personalcaremagazine.com Various bacteria disorders might be
considered as a source of cutaneous dysfunctions like acne, eczema or atopic dermatitis modifying this precious balance. Cosmetics search for 3 main benefits: ■ Rebalancing, pro-biotic, pre-biotic ■ Probiotic-like ■ Anti-microbial effects. In a regulatory approach, the first thing is
conditions of its ecosystem: temperature, pH, hormones, light, UV, lipids, proteins, water. It is mainly influenced by genetics, lifestyle and diet. Each person has their own skin flora composition, distributed from the epidermis until the dermis, which has lifelong qualitative stability, like a personal microbial footprint. This skin microflora is fundamental for skin homeostasis and participates in immune and barrier functions.
Microbiota claims: the era of a new revolution for cosmetics? Currently, the approach of supporting this activity in cosmetics is still in its early stages. Many testing laboratories are studying these new claims looking in the direction of the metagenomic field. The studies of cutaneous flora are complex, and it is not always easy to understand its functionalities and interactions with skin metabolism. The first way is to analyse the genome of the skin flora bacteria. It is a living layer of the skin to be discovered like a new continent of the body. First, we must consider that skin microbiota
does not belong to the epidermis layer of the skin. It is a “foreign” substance of our body: ■ Acting as a resident of the skin and ■ Forming a biofilm at the epidermis surface ■ Maintaining the good conditions of the skin and regulating inflammation, ■ Protecting the body from aggressive environmental conditions and various internal stresses.
that personal care targeting the skin microbiota must be safe following the EC 1223/2009. They must include in their formula only prebiotics, probiotics and postbiotics ingredients that are not listed on the Annex II of the prohibited substances. Moreover, each brand must assess that the microorganism involved in the formula does not produce any toxin. The claims of “skin microbiota” care cannot be misleading, must give sufficient grounds to the consumers. Cosmetics are only allowed to keep the skin healthy and are not allowed to make it healthy or to modify the physico-chemical processes of the epidermis. Personal care, toiletries or cosmetics claiming that they support and protect the skin microbiota are allowed using claims such as ‘supports’ or ‘protects the microbiota’, ‘microbiota friendly’. But these products cannot claim that they stimulate, boost, reduce, or improve the microbiota or its diversity even it is admitted that higher diversity is linked with higher hydration, and less infected skin.
How to evaluate cosmetics activity on the skin microbiota? As the important intra-individual diversity of the cutaneous flora is also associated with a high level of inter-individual variability, the protocols will compare the skin swabbing of the treated zone and of the non-treated or placebo zone, before and after treatment. It is possible to evaluate the balance of the changes. To go deeply into this objectivation, it is also possible to study the microbiota and the skin simultaneously and investigate what are the functions and the metabolic pathways impacted. Analysis of the skin microbiota and the performance of personal care can be directly evaluate analysing the quantity and the quality of the species collected on the skin or scalp samples. Main evaluation opportunities: ■ Counting method at cell level, ■ Fluorescence of the Propionibacterium acnes bacteria on the skin surface. The Visiopor developed by Courage & Khazaka
September 2021 PERSONAL CARE
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