Contrast agent-induced reactions like edema, uicaria, rash, and hypotension are mediated due to
IgG mediated reaction
Anaphylactoid reaction
Type I allergic reaction
IgE mediated reaction
Anaphylactoid reactions are defined as those reactions that produce the same clinical picture with anaphylaxis but are not IgE mediated, occur through a direct nonimmune-mediated release of mediators from mast cells and/or basophils or result from direct complement activation. More common in iodinated contrast media Ref : Ananthanarayana textbook of Microbiology 9th edition Pgno : 163-165
Immunology