Allergic Reactions and Angioedema

Allergic reactions and angioedema are overreactions by the immune system, producing immunoglobulin E (IgE) antibody to an otherwise harmless antigen or allergen. Anaphylaxis is a potentially fatal hypersensitivity reaction involving multiple organ systems that occurs seconds to minutes following exposure to the inciting antigen. Anaphylactoid reactions present with clinically indistinguishable features to anaphylaxis; however, the underlying mechanisms are nonimmunologic (not IgE mediated). Although diagnostic criteria exist to diagnose anaphylaxis, clinically it is important to recognize and treat anaphylaxis immediately. Patients who have experienced anaphylaxis are at risk for recurrent episodes. The long-term prognosis is generally favorable.