Allergic and photoallergic dermatitis from diphenhydramine.

A 52-year-old man developed contact and photoallergic dermatitis caused by diphenhydramine hydrochloride as well as contact dermatitis from paraphenylenediamine. The diphenhydramine photoallergy was elicited by long-wave ultraviolet light. The action spectrum differs from that noted in a recent report in which wavelengths shorter than 320 nm were responsible for eliciting diphenhydramine photoallergy. To the best of my knowledge, this is the third case of diphenhydramine photosensitivity reported in the English literature. The combination of both contact and photosensitivity to diphenhydramine has not previously been described.