This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
Allergic reactions to radiological contrast agents are: 
Select and explain. 
A. Anaphylactic reactions, B. IgE mediated reactions, C. Uicaria, D. Edema
A: Anaphylactic reactions
Answer: A: Anaphylactic reactions 
Explanation: In radiological imaging it is usually believed that the adverse effects of contrast media are non-IgE mediated anaphylactoid reactions, as a result of released vasoactive amines (histamine, serotonin, etc) which trigger the mast cells directly. Since anaphylactoid reaction is not given in the choice, anaphylactic reaction may be the right choice. Ref: Encyclopedia of Diagnostic Imaging By Albe L Bae Pages 44-46