ABSTRACT
Currently, contact allergy to diphenhydramine is rarely reported. Nevertheless, it was stated to be a common cause of allergic contact dermatitis in the USA in the 1980s, although another American author, in 1983, presenting 3 patients sensitized to diphenhydramine, could find only a few other case reports. In the period 1971-1976 inclusive, at St. John's Hospital, London, 7 patients were diagnosed with contact allergy to diphenhydramine and another 6 with probable sensitization. Three cases of contact allergy to diphenhydramine HCl were reported from the USA in 1983. Photopatch tests gave a reaction to diphenhydramine equal to the patch test. In a multicenter study in Italy, performed in the period 1985-1994, one photopatch test reactions was seen to diphenhydramine; the patch test concentration used was not mentioned and relevance was not specified 78% for all photoallergens together. Photopatch testing showed a positive reaction to diphenhydramine HCl 1% pet., whereas a patch test was negative.
