A study of the photostability of Padimate-O (2-ethylhexyl ester of p-dimethylamino-benzoic acid)

The photolytic reactions of p-dimethylaminobenzoic acid and Padimate-O have been investigated to provide a chemical background for the photosensitization of the sunscreen ingredients. The sunscreen ingredients p-dimethylaminobenzoic acid and Padimate-O, currently used as UV-B and UV-A absorbers, were photolyzed in cyclohexane for 140 hours each with a mercury vapor lamp (450 W). p-Dimethylaminobenzoic acid in cyclohexane does not yield any detectible products after irradiation. Irradiation of the Padimate-O in cyclohexane produced four major compounds.