Study of cross-reactivity between proton pump inhibitors.

Several studies have demonstrated different cross-reactivity patterns between proton pump inhibitors (PPIs). The aim of this study was to investigate cross-reactivity between commercially available PPIs and establish a procedure for performing cutaneous tests for verifying PPI allergy. We performed skin prick and intradermal tests with all commercially available PPIs in 5 patients with clinical allergy to omeprazole and observed positive results in all patients. We report 5 cases of immunoglobulin (Ig) E-mediated allergy to omeprazole and document cross-reactivity by skin testing between all the PPIs studied. We also found that the probability of confirming an IgE-mediated mechanism with skin tests decreases with time. Finally, we propose a hypothesis that could explain the different PPI cross-reactivity patterns reported.