Adverse reactions to antihistamines
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ntroduction:H1-antihistamines are widelyused to relieve symptoms of allergic disor-ders. A few skins reactions to H1-antihista-mines have been described in the literature.Histamine H1-antagonists can cause con-tact and photocontact dermatitis, but skinreactions provoked by their systemic useare very rare. We report two cases of anti-histamines-induced urticaria during 7 yearsin our allergy department.Case 1:A 39-year-old woman wasadmitted because of a second cutaneouseruption with the same morphologic fea-tures as before. The first eruption appearedafter 2 h of Cetirizin 10 mg oral intake, thesecond eruption appeared after 1 h ofCetirizin intake. Healing was obtainedafter stopping the medication.Case 2:A 25-years-old man suffering froma drug reaction attributed to the oralintake of Mebhydrolin 50 mg. He is anatopic patient with seasonal perennial rhi-nitis and marked hypersensitivity to thegrass pollen who is receiving inhaled corti-costeroids. He visited because of the gener-alized morbilliform eruptions with pruritusover his whole body, after intake of Meb-hydrolin. Previously, he had presented thesame cutaneous reactions after oral admin-istration of Mebhydrolin.Methods and results:Prick tests with anti-histamines (Mebhydrolin and Cetirizin)were negative. Oral challenge tests withantihistamines were performed. Thepatients developed generalized urticarialeruptions approximately 3 h after intakeMebhydrolin and Cetirizin. These reactionspersisted for 6–12 h.Conclusion:Oral challenge tests with addi-tives are not reliable, as the different for-mulations differ in their production.Although antihistamines are used in aller-gic disorders, allergy to these drugs mustbe considered when cutaneous lesionsappear during the treatment.