512 Impairment of skin microbiota by overcleansing

Abstract

Our skin is daily aggressed by environmental factors and by certain personal care products (cleansers, deodorants, etc).Our obsession with cleanliness may do more harm than good for the balance of our skin’s microbiota and skin health. It has been observed that overcleanliness leads to an impairment of the skin barrier function and of skin microbiome balance leading to increased sensitivity, irritation and dryness. We explored the effect of a common surfactant found in hygiene products, on the physical skin and microbiotic barrier in vivo. At first, we applied SLS (Sodium Lauryl Sulfate, 0.5% occlusive patch for 24h) and we explored its effect on the skin microbiota using metagenomic sequencing (16S rDNA) before and 1 day after SLS application. Secondly, we explored skin microbiota and skin barrier function evolution over 7 days after a 1% SLS challenge in the presence of a formula containing purified rapeseed phytosterols and one containing its vehicle. Skin barrier function was assessed before, after SLS and 7 days after applying phytosterols and vehicle by measuring TEWL. Finally, skin microbiota recovery after a 0.5% SLS patch in presence of the same formula containing phytosterols was assessed at the same timepoint; (16S metasequencing). We confirmed that the surfactant impaired skin barrier function and evidenced that it decreased the commensal bacteria while increasing the opportunistic pathogenic bacteria. At the phylum level actinobacteria were decreased by 14% and at the family level, corynebacteriaceae, micrococcaceae and propionibacteriacea were decreased (-42%, -34%, -11%). At the genus level corynebacterium, micrococcus, paracoccus and propionibacterium were decreased (-42%, -39%, -36%, -11%), whereas pseudomonas and pantoea were increased (x2, x117). Interesting results were also obtained on staphylococcus (+38%), but a more resolutive technic is necessary to discriminate between strains. To counterbalance these SLS induced-modifications, we evidenced that purified phytosterols provide benefits to restore skin barrier and microbial skin flora.