The concept of skin microbiota is not really clear and more accurate approaches are necessary to explain how microbial flora can influence skin biophysical parameters in healthy individuals and in pathology patients with non-infectious skin disease. The aim of this work is to provide a suitable, fast and reproducible protocol to correlate skin parameters with the composition of skin microbiota. For this purpose, the work was split into two main phases. The first phase was focused on the selection of volunteers by the administration of a specific questionnaire. The skin microbiota was then collected from the forehead of selected volunteers as a test area and from the shoulder as control area. On the same skin area, the biophysical parameters, such as trans-epidermal water loss (TEWL), sebum level (SL), porphyrin intensity, keratin content and stratum corneum water content were taken. All parameters were taken at t0 and after 15 days without changes in the volunteers’ lifestyle. A strong correlation was found between forehead and shoulder area for porphyrin intensity, pH and TEWL parameters, and between Cutibacterium acnes and some biophysical parameters both in the forehead and the shoulder area. The procedural setup in this work represents the starting point for evaluating problematic skins and the efficacy of cosmetic products or treatment against skin dysbiosis.

Air pollution is known to affect skin health, but tools to objectively measure individual exposure based on skin responses are limited. This study introduces the Exposure Intensity Index (EII), a novel tool that correlates lifestyle-related pollution exposure with skin parameters. A panel of 250 women residing in Lombardy completed a detailed questionnaire on socio-demographic features and daily habits, from which an exposure score was derived. Non-invasive bioengineering techniques were used to assess skin parameters, focusing on inflammation-related signs. A positive correlation emerged between exposure scores and variations in specific skin parameters, suggesting a link between daily pollution exposure and skin alterations. The EII emerges as a preliminary exploratory approach to estimate environmental impact on the skin through its correlation with biophysical parameters. It may offer future value for subject selection in in vivo testing of antipollution cosmetic claims.