Leon-Yum Phoon, MD; Chee-Fah Chong, MD; Tzong-Luen Wang, MD, PhD

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Abstract ---Anaphylactic shock is medical emergency characterized by circulatory collapse resulted from severe acute allergic reactions, namely anaphylaxis and anaphylactoid reaction. Anaphylaxis is an acute, systemic, IgE-mediated, immediate hypersensitivity reaction caused by the release of mediators by mast cells and basophils after exposure to antigens. A diversity of antigens could trigger anaphylaxis and the most common causes are medications, insect stings and foods. Whereas anaphylactoid reaction is IgE-independent and contrast media is the widely known triggering agent. Anaphlaxis is a clinical diagnosis with a combinations of symptoms and signs that include weakness, dizziness, flushing, angioedema, urticaria of the skin, congestion, and sneezing. More severe symptoms include upper respiratory tract obstruction, hypotension, vascular collapse associated with angioedema and urticaria, gastrointestinal distress, cardiovascular arrhythmias, and arrest. Prompt administration of epinephrine is critical for the success in the treatment of acute anaphylaxis. H1 and H2 antihistamines, corticosteroids and appropriate fluid supplement should be given. Infusion of inotropic agents may be required. When the symptoms subside, observation in the emergency department before discharge is prudent.