Introduction
Omeprazole is a proton pump inhibitor (PPI) that is indicated for gastroduodenal ulcer, gastroesophageal reflux and hypersecretory states. It has an excellent safety profile with a low incidence of adverse effects. Reported side effects of omeprazole are headache, constipation, diarrhea and, more rarely, elevated transaminases and hypersensitivity(1). Most of these latter reactions (86%) to PPIs seem to be IgE- mediated, and manifests clinically by urticaria, angioedema, hypotension, and dyspnea (2). Some sporadic cases of omeprazole-induced urticaria have been described in the medical literature and confirmed by skin tests considered as a reliable tool for establishing causality in the presence of concomitant drugs. Some case reports and studies have shown that cross-reactivity among PPIs does exist and is likely related to the similar organic structure of them(3). However, hypersensitivity could be selective to a single PPI. In this context, we report herein a clinical observation of omeprazole-induced urticaria without any cross-reactivity to other PPIs, confirmed by skin and provocation tests.