Coumarin Derivatives, But Not Coumarin Itself, Cause Skin Irritation Via Topical Delivery

The study investigated the skin absorption and potential irritation caused by coumarin and its derivatives when applied topically. It was found that while coumarin itself did not significantly alter protein biomarkers related to skin irritation, its derivatives, such as osthole, byakangelicin, and 7-hydroxycoumarin, did cause skin irritation and increased transepidermal water loss. Osthole, in particular, showed the highest skin accumulation due to its lipophilic nature. The research highlighted that hair follicles were a significant pathway for coumarin transport, and the irritation was primarily due to the derivatives rather than coumarin itself. The study emphasized the importance of understanding the dermal effects of these compounds, especially given their widespread use in cosmetic products.