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.