Characterization of Photosensitizing Effects by Topical Delivery of Alpha-Terthienyl and UVA

The study investigated the phototoxic effects of alpha-terthienyl (a-T), a compound derived from marigolds, when applied topically and exposed to UVA radiation. Conducted on guinea pig skin, the research demonstrated that a-T in a 3% Azone gel penetrated the skin in a dose-dependent manner, with maximum sensitization occurring 1 hour after application. The phototoxic response included erythema, edema, crusting, erosion, and inhibition of hair growth, observed 72 hours to 7 days post-irradiation. The study suggested that topical a-T combined with UVA could be a safer alternative for photochemotherapy in treating psoriasis and other skin diseases, as it does not interact with DNA and avoids the carcinogenic risks associated with other treatments like psoralens.