Contrast agent-induced reactions like edema, uicaria, rash, and hypotension are mediated due to

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