Influence of Cosmetic Skincare Products with pH < 5 on the Skin Microbiome: A Randomized Clinical Evaluation.

Introduction: The human skin acts as a protective barrier against external pathogens and hosts a diverse microbiome consisting of bacteria, fungi, viruses, and archaea. Disruptions to the skin microbiome can impact immune function, leading to inflammatory and autoimmune conditions. The importance of pH for the microbiome is paramount. Cosmetic skincare products interact with the skin microbiome and skin pH, playing a key role in maintaining microbial balance. Research suggests that products with non-physiological pH levels may disrupt the skin microbiota. Our clinical study aimed to evaluate the effects of low-pH cosmetic products (pH < 5) on the skin microbiome, contributing to improved skin health.

Methods: The clinical study focused on evaluating the skin microbiome diversity following the application for 28 days of four different low-pH cosmetic products (vitamin C, resveratrol, a collagen mask, and a native algae mask) on the forearms of post-menopausal women with skin pH > 5.5.

Results: The diversity of the natural skin microbiome increased consistently throughout the study, evident in both the untreated area and after the application of the Vitamin C Concentrate, Resveratrol Concentrate, Collagen Mask, and Native Algae Mask, as indicated by Shannon's diversity index. The native algae mask notably reduced the Corynebacterium genus and significantly lowered the pH. The skin pH changes corresponded with microbiota stability.

Conclusions: In conclusion, enhanced diversity of the natural skin microbiome was observed over the study duration. None of the investigational products caused significant disruption to the skin microbiome diversity, as evidenced by the stable Shannon's diversity index and relative abundance of specific genera. Notably, the native algae mask significantly decreased the presence of the opportunistic pathogenic Corynebacterium genus, which is likely attributable to a minor reduction in skin pH following extended product use. The findings suggest that the use of low-pH skincare products, like the native algae mask, do not disrupt skin microbiome diversity and may have the potential to positively impact skin microbiome diversity and health by reducing certain pathogenic microbial populations.