The present application is directed to the use of X-ray contrast media that act as universal antigens that are labeled herein as "pseudoantigens." X-ray contrast media have the potential to exist in an aggregated state that is greater in increased concentrations. In this aggregated state, contrast media assume the role of multivalent antigens and can successfully compete with any other antigens involved in antibody-antigen reactions that lead to anaphylaxis. In this competition, the large quantity of contrast media serves to inhibit the adverse effects of antibody-antigen reactions without the contrast media itself creating antibodies or creating toxicity problems.