E-Mail karger@karger.com Original Paper Int Arch Allergy Immunol 2016;171:54–60 DOI: 10.1159/000450952 Management of Hypersensitivity Reactions to Proton Pump Inhibitors: A Retrospective Experience Seçil Kepil Özdemir   a Ferda Öner Erkekol   b Derya Ünal   e Suna Büyüköztürk   e Aslı Gelincik   e Adile Berna Dursun   f Gül Karakaya   c Sevim Bavbek   d a  Division of Allergy and Immunology, Dışkapı Yıldırım Beyazıt Training and Research Hospital, b  Division of Allergy and Immunology, Department of Chest Diseases, Atatürk Chest Diseases and Thoracic Surgery Training and Research Hospital, c  Division of Allergy and Immunology, Department of Chest Diseases, Hacettepe University School of Medicine, and d  Division of Allergy and Immunology, Department of Chest Diseases, University School of Medicine, Ankara, e  Division of Allergy and Immunology, Department of Internal Medicine, Faculty of Medicine, İstanbul University, İstanbul, and f  Division of Allergy and Immunology, Department of Internal Medicine, Recep Tayyip Erdoğan University School of Medicine, Rize, Turkey zole was the most commonly suspected drug with 41 patients (68.3%), followed by pantoprazole in 12 patients (20.0%), esomeprazole in 6 (10.0%), rabeprazole in 4 (6.7%), and omeprazole in 1 (1.7%). Anaphylaxis (40 patients, 66.7%) was the most common clinical presentation followed by ur- ticaria (17 patients, 28.3%). Diagnostic skin tests with the cul- prit PPI were positive in 13/26 patients (50.0%). Diagnostic oral-provocation tests were negative in 6/8 patients; 5 of these 6 patients had skin test results with the culprit PPI, and all were negative. Ten patients had at least 1 cross-reactivity. Extensive cross-reactivity (between >2 PPIs) was detected in 4 patients. Conclusions: Lansoprazole was the most fre- quently implicated drug and anaphylaxis was the most frequent manifestation of PPI-induced hypersensitivity re- actions. Physicians should be aware of the possible cross- reactivity among PPIs; however, a safe, alternative PPI can usually be detected by a thorough drug allergy workup. © 2016 S. Karger AG, Basel Keywords Cross-reactivity · Drug allergy · Hypersensitivity · Proton pump inhibitors · Skin tests Abstract Background: We previously reported perfect specificity and low sensitivity of skin tests in proton pump inhibitor (PPI)- induced immediate hypersensitivity reactions in a prospec- tive multicenter study. Here, in a retrospective study, we aimed to further evaluate the diagnostic workup proce- dures and characteristics of the patients with suspected PPI hypersensitivity. Methods: This national multicenter study was conducted as a retrospective chart review of patients with a history of PPI-induced immediate hypersensitivity reaction. A total of 60 patients were included. Results of di- agnostic workup procedures (standardized skin-prick, intra- dermal, and oral-provocation tests with PPIs) and the char- acteristics of the patients were analyzed. Results: Lansopra- Received: May 20, 2016 Accepted after revision: September 20, 2016 Published online: November 12, 2016 Correspondence to: Prof. Sevim Bavbek Division of Allergy and Clinical Immunology, Department of Chest Diseases Ankara University School of Medicine TR–06100 Ankara (Turkey) E-Mail bavbek  @  medicine.ankara.edu.tr © 2016 S. Karger AG, Basel www.karger.com/iaa