The skin is the first layer of defence of our body towards the environment. It is essential to protect us from physical and biological impact. At the same time, the skin is a flourishing ecosystem inhabited by different microorganisms that co-evolved with the human host, leading to a beneficial symbiosis between the skin and its microbiome. The awareness of the need to apply sun protection is rising as more and more people start considering skin aging and skin cancer. At the same time, consumers concern about the human and environmental safety of UV filters. Accordingly, comprehensive studies on the safety profile of UV filters are needed. Only a few studies investigated potential effects of light/UV on cutaneous microorganisms being far from any systematic understanding. Many consumers already expect that their sun care formula maintains the skin microbiome balance or respects the microbiome.
We performed an in vivo study to investigate the impact of sunscreens on the human skin microbiome. Emulsions containing different UV filter combinations as well as a placebo without any UV filter were applied to the forearms of 23 healthy persons. The products were applied three times daily for a duration of two weeks to mimic the regular application during a summer vacation. At the beginning before the first application and after two weeks application the microbiome was sampled with swabs and the samples analysed with 16S rRNA sequence analysis.
The skin microbiome of the participants was found to be stable in its composition over the duration of the study. While typical representatives of a healthy skin microbiome were identified, their average contribution was not impacted neither by the placebo emulsion nor by any product containing UV filters.
The outcome of this study fulfilled the customer expectation regarding save sun care products.