Cutaneous drug eruption with two antihistaminic drugs of a same chemical family: cetirizine and hydroxyzine

BACKGROUND: H1-antihistamines are widely used to relieve symptoms of allergic disorders. A few skins reactions to H1-antihistamines have been described in the literature. We report the first case of cutaneous drug eruption as fixed drug eruption with 2 antihistamines of the same chemical family: cetirizine and hydroxyzine. CASE REPORT: A 73 year-old man was admitted because of a third cutaneous eruption with the same morphologic features of the same sites as before. The first and second eruption appeared after 4 hours of cetirizine intake, the third eruption appeared after 4 hours of hydroxyzine intake. Healing was obtained after stopping the medication. Histology showed induced drug reaction. Patch tests with cetirizine and hydroxyzine were negative, except false positivity with dimethylsulfoxide vehicles. DISCUSSION: The diagnosis of cutaneous drug eruption as non pigmenting fixed drug eruption related to cetirizine and hydroxyzine was retained. Allergy to both H1 antihistamines can be explained by the fact that they've got the same chemical node that is piperazine, and by the fact that cetirizine is the main metabolite of hydroxyzine. Oral test provocation was omitted because the patient had already reexposed himself to the drugs. To identify the drug responsible for fixed drug eruption, peroral provocation tests are the most valuable method, but carry the risk of a strong reaction. Some authors use patch tests, but their positivity is inconstant. Their interest in fixed drug eruption is undergoing assessment.