Anaphylaxis to radiographic contrast media

Purpose of review: Radiographic contrast media (RCM) are increasingly used in modern diagnostic medicine. Hypersensitivity reactions to nonionic RCM still occur in a significant number of exposed patients, because of the increased use of contrasted radiological investigations. Hypersensitivity reactions may be divided into immediate (<1 h of administration) and nonimmediate responses (>1 h). Immediate reactions present with anaphylaxis. Recent findings: Although described less commonly, anaphylaxis to gadolinium contrast media have been increasingly reported in recent literature. In most patients, immunoglobulin (IgE)-mediated allergy cannot be demonstrated and the underlying mechanism remains unknown. In some patients, positive skin tests, specific IgE antibodies or specific cellular tests have been demonstrated. It may be speculated that more allergic reactions could be described, if more adequate methods were developed. Skin prick tests and intradermal tests with 1:10 diluted RCM are specific and confirm the diagnosis of RCM hypersensitivity. Summary: There are not enough data yet about the value of skin tests for the selection of a 'well tolerated' RCM. Premedication of previous reactors is common among radiologists. However, breakthrough reactions are a concern and physicians should not rely on the efficacy of pharmacological premedication. Instead, radiologists should be prepared to treat severe RCM-induced allergic reactions in their practice.