Three cases of contact dermatitis caused by an ethanolamine antihistamine, diphenhydramine hydrochloride (Benadryl), are described. Patients who develop contact dermatitis from it should avoid its oral or parenteral administration because they may develop a localized or generalized flare of dermatitis. Dimenhydrinate (Dramamine), clemastine fumarate (Tavist), carbinoxamine maleate (Clistin-D), and doxylamine succinate (Decapryn) are also ethanolamine antihistamines. Since they may cross-react with diphenhydramine hydrochloride, they should be avoided in sensitive patients.