Five cases of photocontact dermatitis due to topical ketoprofen: photopatch testing and cross-reaction study

Background: In parallel with the popular usage of topical ketoprofen, the n umber of reported cases of ketoprofen-induced photoallergic contact dermati tis has been increasing. It is clinically important to know the cross-react ivity of ketoprofen in order to avoid cross-sensitization caused by several structurally similar non-steroidal anti-inflammatory drugs (NSAID) on the market. Methods: To evaluate the spectrum of cross sensitization, photopatch testin g was performed on five patients with ketoprofen-induced photoallergic cont act dermatitis using ketoprofen and other structurally similar chemicals, s uch as oxybenzone, tiaprofenic acid and suprofen. Results: All five patients reacted positively to ketoprofen or ketoprofen p laster on photopatch testing. All four patients photopatch tested with rela ted chemicals showed cross-photosensitization with tiaprofenic acid and sup rofen, However, none of the patients reacted positively to oxybenzone. Conclusion: Either the diphenylketone moiety or a structurally similar tiop hene-phenylketone moiety is important as the antigenic determinants of keto profen photoallergy, The arylpropionic acid side chain would not be involve d.