• Axel Trautmann, Knut Brockow, Valeria Behle, and Johanna Stoevesandt.
• Department of Dermatology and Allergy, University Hospital Würzburg, Würzburg, Germany. Electronic address: trautmann_a@ukw.de.
• J Allergy Clin Immunol Pract. 2019 Sep 1; 7 (7): 2218-2224.

BackgroundHypersensitivity reactions occurring within minutes after intravascular injection of iodinated radiocontrast media (RCM) are not rare and have been previously considered to be nonallergic. However, in the last decades, evidence is increasing that genuine RCM allergy may present as either full-blown anaphylaxis or delayed exanthematous skin reaction.ObjectivesWe aimed to assess whether allergy diagnostics including skin and provocation testing can differentiate between nonallergic and allergic RCM hypersensitivity by identifying the causative RCM as well as tolerated alternative RCM.MethodsWe retrospectively evaluated clinical and diagnostic data from 45 consecutive patients with RCM hypersensitivity.ResultsImmediate nonallergic RCM hypersensitivity was diagnosed in 21 patients, immediate-type RCM allergy in 11, delayed-type RCM allergy in 11, and delayed-type iodine allergy in 2. All patients with immediate-type RCM allergy had a history of moderate to severe anaphylaxis. Eleven of 13 patients with delayed-type allergic reactions including the 2 cases of iodine allergy suffered from maculopapular exanthem developing several hours to days after exposure, 1 was a systemic hypersensitivity syndrome, and 1 a fixed drug eruption. Of 18 RCM-allergic patients tested, all tolerated an alternative RCM in the intravenous provocation.ConclusionsThe diagnostic sensitivity of intradermal RCM testing to identify allergic patients is high in both immediate-type and delayed-type RCM allergy. Intravenous provocation with a skin test-negative RCM is safe and enables identification of a tolerated alternative RCM. Additional skin testing of iodine solution is required to identify patients with iodine allergy.Copyright © 2019 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

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