Drug allergy to cetirizine: fixed drug eruption

Drug hypersensitivity reactions are one of the most complex and difficult-to-diagnose problems in the modern practice of an allergist-immunologist. Fixed drug eruption occurs in 14–22 % cases of delayed-type drug allergy skin lesions. The most common triggers of fixed drug eruption are fluconazole, barbiturates, nonsteroidal anti-inflammatory drugs (more often coxibs), metamizole sodium, and antibacterial sulfonamides. Antihistamines are not typical representatives of drugs that cause drug allergies, including fixed drug erythema. However, it is important to remember that antihistamines can also be a cause of drug allergy. This article presents a clinical case of a female patient with a history of multiple episodes in the form of fixed drug eruption. Key information about this type of drug allergy, including the pathogenesis of the reaction and diagnostic methods, is described in detail. During the diagnostic process, drug testing was performed: a local provocative patch test and a provocative oral test. Based on the results of provocative testing, a cause-and-effect relationship between the intake of cetirizine and the appearance of characteristic erythematous rashes was confirmed. A diagnosis of fixed drug eruption to cetirizine was established. Thus, for confirming the diagnosis of fixed drug eruption to a rare trigger, especially with an ambiguous medical history, decisive importance lies with drug provocation test.