Purpose. The etiology of severe reactions following injection of iodinated contrast agents is the subject of controversy. No consensus has been established regarding the management of patients at risk, risk factors and premedication because in most cases published no diagnostic exploration has been carried out on patients who have experienced a severe reaction.

Material and Methods. Diagnosis of drug anaphylaxis is based on clinical history, proof of mediator release and drug-specific IgE antibodies (when the technique is available) or cutaneous tests (when direct technique is not available).

Results . This approach has been adopted for etiologic diagnosis of 5 clinical cases of severe anaphylactoid reactions (including one death) following the injection of ionic and non ionic contrast agents. Clinical symptoms, biology and cutaneous tests are consistent with anaphylaxis.

Conclusion. Any patient who has had a severe anaphylactoid reaction following injection of a contrast agent should undergo an allergological assessment to confirm the diagnosis and identify the culprit contrast agent. Indeed, no premedication has proved efficient for the prevention of subsequent allergic reactions.