Acidic Skin Care Promotes Cutaneous Microbiome Recovery And Skin Physiology in An Acute Stratum Corneum Stress Model

Abstract Background: The skin microbiome and skin physiology are important indicators of the epidermal homeostasis status. Stress models are used to reveal pathological conditions and modulating effects. The recovery phase served to investigate the cutaneous microbiome in relation to skin physiology after mild tape stripping without treatment compared to two cosmetic leave-on lotions (pH 5.5 vs. pH 9.3). Material and MethodsThe prospective, randomized, controlled study was performed in 25 healthy volunteers: The microbiome was assessed via swabs and subsequent 16S-rRNA-gene amplicon sequencing. Skin physiology was analyzed in terms of barrier function, stratum corneum hydration, surface-pH, skin color non-invasively. All parameters were assessed before and immediately after 2hrs., 2 days and 7 days after tape stripping. Lotion A (pH 5.5) and the identical lotion B (pH 9.3) were applied 2-times per day for 7 days on the volar forearm.ResultsTape stripping reduced the alpha diversity with a recovery over 7 days without treatment. Both lotions significantly accelerated the recovery of the alphadiversity already after 2 days with a slightly higher rate for lotion A (pH 5.5). After tape stripping, the relative abundance of Proteobacteria was increased, whereas Actinobacteria were reduced. Further, mean relative abundances of typical skin-associated genera were reduced after tape stripping. Taxa compositions returned to normal levels after 7 days in all treatment groups, and an accelerated normalization could be observerd with treatment by both lotions already after tow days. A significant difference in skin-pH was observed at day2 and day7 with an increased pH in lotion B treatment. Both lotions induced an increase in stratum corneum hydration. Barrier function was only changed by tape stripping. DiscussionThe study proved the suitability of an experimental stress model in the assessment of skin surface microbiome in relation to skin physiology. Stratum corneum hydration increased significantly with both lotions already at day 2. Microbiome parameters (alpha-diversity, mean relative taxa, abundance of selected genera) normalized over 2-7 days. Three potential mechanisms could be responsible for the accelerated normalization: a) optimized hydration during the recovery phase b) the composition of the lotion, c) acidic pH of the lotion.