Anaphylactoid Reactions to Radiopaque Contrast Dye

To the Editor: In the article entitled “Mechanisms of Drug-Induced Allergy,” published in the March 2009 issue of Mayo Clinic Proceedings, Schnyder and Pichler¹ did not discuss the etiology of more than 99% of the anaphylactoid reactions to radiopaque contrast dye. These chemicals cause nonimmunologic release of histamine and other vasoactive amines in the body, resulting in a condition similar to anaphylaxis.