Cutaneous drug eruption induced by antihistamines.

Topical application of antihistamines commonly leads to sensitization for patients, but systemic administration of antihistamines rarely induces allergic hypersensitivity, which is mainly linked to phenothiazine-derived and piperazine-derived compounds. We report a 70-year-old woman whose medical history included lichen planus, and who was referred by the dermatology department of our hospital for suspected allergy to corticosteroids. The reason for referral was that on the fourth day of treatment with prednisone and hydroxyzine, the patient presented a bilateral highly pruritic palmar erythema that evolved to a generalized morbilliform rash with subsequent complete desquamation. At a later time, she took cetirizine for a cold, and developed palmar erythema and desquamation. Skin tests (prick and intradermal tests) were performed with steroids, and patch tests (read after 48 and 96 h) with corticosteroids and antihistamines. Controlled oral challenge tests were performed with prednisone and with an alternative antihistamine. Skin tests were negative for all corticosteroids. Patch tests were negative for all corticosteroids, but the antihistamine test was positive for hydroxyzine. Oral challenge with prednisone and dexchlorpheniramine was negative. The patient was diagnosed with cutaneous drug eruption from hydroxyzine and cetirizine. We consider it is important to assess every patient whose skin condition worsens after treatment with antihistamines, especially hydroxyzine, because it is known that antihistamines are often not recognised as the culprit in cases of cutaneous eruption.