Encyclopedia > Anaphylaxis

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Anaphylaxis is a severe and rapid allergic systemic reaction to contact with an allergenic trigger substance (atopic or anaphylactic hypersensitivity). Minute amounts of trigger substances may cause a life-threatening anaphylactic reaction. Anaphylaxis may occur after ingestion, inhalation, skin contact or injection of a trigger substance.

Symptoms can include respiratory symptoms; hypotension (low blood pressure); fainting; unconsciousness; urticaria (pruritic wheals); angioedema (swelling); and itching. The symptoms are related to the action of immunoglobulin E (IgE) which acts to release histamine[?] and other mediator substances from mast cells. Histamine induces, beside other effects, vasodilation[?] and bronchospasm[?] (constriction of the airways).

The most severe type of anaphylaxis is termed anaphylactic shock, which may lead to circulatory collapse and death.

Common causative agents in humans include food ingredients (nuts, peanuts, fruits), drugs (e.g. penicillin, contrast media[?], NSAIDs), latex, bee or wasp stings.

The treatment of anaphylaxis aims at the cellular hypersensitivity reaction as well as at the symptoms. Antihistamine drugs (which inhibit the effects of histamine at histamine receptors) are usually not sufficient in anaphylaxis, and high doses of intravenous corticosteroids are often required. Hypotension is treated with intravenous fluids and sometimes vasoconstrictor drugs. For bronchospasm brochodilator drugs are used. In severe cases, immediate treatment with epinephrine may be lifesaving. In the absence of medical help, an injection of epinephrine delivered with a device such as an Epi-pen[?] may be helpful.

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