Anaphylaxis.

Anaphylaxis is an amplified, harmful immunologic reaction that occurs after re-exposure to an antigen to which an organism has become sensitive. True anaphylaxis is a systemic reaction caused by antigen-specific cross-linking of IgE molecules or complement proteins on the surface of tissue mast cells and peripheral blood basophils, resulting in the immediate release of potent mediators. Immediate systemic reactions that resemble anaphylaxis but are not caused by an IgE-mediated immune response are referred to as anaphylactoid reactions. It is important for physicians, especially those who treat allergies, to understand the pathophysiology, know the treatment for, and recognize the clinical signs of anaphylaxis.