The 26th conference of the International Federation of Societies of Cosmetic Chemists (IFSCC) was held virtually by the Mexican Society, taking place 18th–28th October 2021.
Here we provide a brief overview of some of the most exciting research shared at the conference in relation to the skin and its associated microbiome – covering topics such as sensitive skin, the antioxidant potential of Cutibacterium acnes phylotypes, the importance of Lactobacillus for aged skin, and the impact of certain ingredients on our skin microbiota…
Skin microbiota composition
Yuan Chao from the Shanghai Skin Disease Hospital of Tongji Medical University reported on the facial skin microbiome status and skin barrier function in Asian subjects with sensitive skin. As expected, the sensitive skin subjects presented with an abnormal sensation score to a lactic acid sting test (but not transepidermal water loss; TEWL). Surprisingly, using 16S-rRNA sequencing, no differences were found in the relative frequency of skin microbiota phyla (Actinobacteria and Firmicutes) or genera (Proteobacteria or Propionibacteria, Paracoccus and Corynebacteria). However, when examining the frequency of the microbiota at the genus level, several differences were observed between the sensitive and non-sensitive subjects, with the Shannon diversity index being the lowest in the sensitive skin subjects. These differences may be related to DSM’s work on the biochemical differences of the stratum corneum (SC) in subjects with sensitive skin (greater presence of immature corneocyte envelopes associated with lower transglutaminase activity and lower natural moisturizing factors (NMF)). Improving SC biochemistry may aid in control of the microbiome, and in sensitivity to lactic acid.
Carine Francis from L’Oreal published on Cutibacterium acnes phylotypes and antioxidant potential in subjects of different ages. IA-3 strains were predominant in aged skin and I-A2 in young skin, whereas IA-1, 1B-3 and II strains were equal in abundance between the two age groups. Importantly, the antioxidant protein expression of RoxP, SOD and Catalase were highest in the IA-1 and IA-2 strains and lower in the IA-3 strains (and lowest of all in type II strains). Thus, these bacterial genotypes have different antioxidant potential, with those isolated on aged subjects having the least antioxidant potential. Naturally these antioxidant enzymes protect Cutibacteria, but if secreted they may influence SC antioxidant potential. This may be important as the level of SC catalase is known to be decreased in UV- and pollutant-exposed skin. DSM has shown reduced levels of catalase in the SC corneome of photodamaged facial skin.
These findings are also important for the work of Louis Danoux, which examined C. acnes ribotype in subjects with acne (phylotype I increased and II decreased i.e. those with the least amount of antioxidant enzymes). Importantly, Danoux and team found that the effects of antimicrobial peptides were greater on IA-1 strains.
Sabrina Leoty-Okombi from chemical company BASF studied the microbiome in wrinkles of Caucasian skin. Increases in alpha diversity were observed in the aged group, with reduced C. acnes and higher levels of Corynebacterium kroppenstedtii and Veillonella parvula. Decreased levels of lactic acid bacteria such as Lactobacillus crispatus were observed in wrinkled areas. Lipid analysis showed decreased sterols, docosanol and octadecanoic acid that may be related to these changes. These findings emphasize the potential importance of Lactobacillus bacteria on aged skin, and that their metabolites may be beneficial. L-lactic acid is a well-known anti-aging ingredient.
The effect of ingredients on skin microbiota
Many agents that influence the skin microbiome were discussed. Among them was the naturally protective effect of Staphylococcus epidermidis inhibiting C. acnes (IA-1) via the production of succinic acid with biotic ingredients such as sucrose and the effect of Mango leaf extract, essential oils from Nigerian bush tea (containing monoterpenoids, 1,8-cineole and terpinene-4-ol) and Mexican oregano (containing carvacrol and thymol), South African Plectranthus, humulus lupulus, erythritol and antimicrobial peptides (IK-16-1 based on skin beta-defensins).
The most interesting effects were those related to the reported changes to the skin microbiome above, where Lactobacillus plantarum HEAL19 has been shown to be useful in supporting atopic dermatitis, decreasing skin redness and TEWL. Moreover, improvements in skin and cellular biochemistry were shown (increased filaggrin levels, increased antimicrobial peptide levels and decreased inflammatory markers). Furthermore, decreased levels of Staphylococcus species were shown after treatment. Similar effects were observed with use of Lactobacillus paracasei.
A clear example of establishing the effects of ingredients on the facial microbiome is the work from DSM and Mageline, who examined facial skin microbiome modulation by the natural prebiotic extract: Epilobium fleischeri. DSM, with the help of Newtone technologies, have pioneered facial mapping approaches for a variety of skin parameters. They have now utilized this technology to better visualize the enrichment of S. epidermidis and other beneficial bacteria following four weeks of product application.
Overall, IFSCC 2021 was an excellent conference, reporting the latest findings for our understanding of the skin microbiome and approaches for its modulation.