Photodermatitis from topical phenothiazines: A case series

Background In Europe, contact photosensitivity to phenothiazines is well‐known, particularly in southern countries. Topical phenothiazines are widely used and sold over‐the‐counter (OTC) for the treatment of mosquito bites and pruritus in France. Objective To report a series of cases with photodermatitis following use of topical phenothiazines. Method A retrospective study of cases of contact dermatitis from phenothiazines seen in French photodermatology centers was performed. Results In all, 14 patients with a diagnosis of contact dermatitis from phenothiazines were included. These patients developed eczema on the application sites, and in 13 the eruption spread to photodistributed sites. Topical products containing isothipendyl were the most common cause of photodermatitis. One patient had photoaggravated eczema due to promethazine cream. All patients stopped using topical phenothiazines and were treated successfully with topical corticosteroids. One patient relapsed and developed persistent light eruption. In all of the nine cases tested, photopatch testing to the topical phenothiazine used “as is” was positive. Isothipendyl, chlorproethazine, and the excipients were not tested. Photopatch tests to chlorpromazine and promethazine were positive in 8 of 12 and 7 of 13 tested, respectively. Conclusion Use of isothipendyl and promethazine as OTC (or even prescribed) drugs needs to be limited due to severe reactions and sensitization to other phenothiazines that consequently will have to be avoided. In France, topical phenothiazines are used widely and sold over the counter (OTC) for the treatment of mosquito bites and pruritus. We report a series of photodermatitis from topical phenothiazines. In our cases, contact photodermatitis was due to isothipendyl (13/14) and promethazine (1/14). Photopatch tests were positive to topical phenothiazine products tested “as is” (9/9), and to chlorpromazine (8/12), and promethazine (7/13). Use of isothipendyl and promethazine as OTC drugs (or even prescribed) needs to be limited.