Anaphylaxis is a life threatening medical emergency in which the possibility for patient morbidity and mortality is high. It is the most serious of allergic disorders. An understanding of the pathophysiology of anaphylaxis and recognition of symptoms is paramount for its diagnosis. The term anaphylaxis refers to a generalized allergic reaction that results from a type I immunologic reaction. IgE activation of mast cells and basophils results in the release of preformed mediatiors including histamine, prostaglandins, and leukotrienes. These mediators induce vascular permeability, vascular smooth muscle relaxation and constriction of bronchial smooth muscles. Anaphylactoid reactions are clinically and pathologically similar but are not IgE mediated. This pathophysiologic sequence of events leads to the clinical manifestations of anaphylaxis including urticaria, angioedema, pruritus, and bronchospasms, eventually leading to hypotension and death if left untreated. This article discusses current demographics, causes and pathophysiology of anaphylaxis and provides guidelines for the treatment of anaphylaxis. The importance of prompt and correct treatment with adrenaline as well as thorough medical evaluation is also reviewed.