Anaphylaxis is a rapid, potentially fatal, immediate hypersensitivity reaction. Preformed and newly formed biochemical mediators, including histamine, tryptase, carboxypeptidase A, prostaglandin D2, leukotrienes, and platelet-activating factor (PAF) are released systematically during the degranulation of mast cells and basophils. PAF is a proinflammatory phospholipid, synthesized and secreted by mast cells, monocytes and fixed tissue macrophages whose binding to its receptor on target cell-platelet, monocytes, macrophages, and neutrophils results in many of the manifestation of acute allergic reaction and anaphylaxis.