anaphylaxis

anaphylaxis , hypersensitive state that may develop after introduction of a foreign protein or other antigen into the body tissues. When an anaphylactic state exists, a second dose of the same protein (commonly an antibiotic such as penicillin, or certain insect venoms) will cause a violent allergic reaction. Anaphylaxis results from the production of specific antibodies in the tissues in very high concentration; the violent reaction is produced by the neutralization of antigens by the antibodies. The histamines released during the reaction are thought to cause the most damage, i.e., severe vasodilation and loss of capillary fluid, resulting in circulatory collapse. Other symptoms include urticaria or edema, choking, coughing, shock, and loss of consciousness. Death may occur within 5 to 10 min if no medical help is available. Anaphylaxis differs from immunity ; in immunity, antibodies circulate in the blood and neutralize antigens without producing a violent reaction. See also allergy ; serum sickness .

anaphylaxis An abnormal immune response that occurs when an individual previously exposed to a particular antigen is re-exposed to the same antigen. Anaphylaxis may follow an insect bite or the injection of a drug (such as penicillin). It is caused by the release of histamine and similar substances and may produce a localized reaction or a more generalized and severe one, with difficulty in breathing, pallor, or drop in blood pressure, unconsciousness, and possibly heart failure and death. See also allergy.

anaphylaxis (ană-fil-aks-iss) n. an emergency condition resulting from an abnormal and immediate allergic response to a substance to which the body has become intensely sensitized. It results in flushing, itching, nausea and vomiting, swelling of the mouth and tongue and airway enough to often cause obstruction, wheezing, a sudden drop in blood pressure, and even sudden death. In this extreme form it is called anaphylactic shock. Treatment, which must be given immediately, consists of adrenaline (epinephrine) injection, oxygen with possible advanced support of the airway, intravenous fluids, intravenous corticosteroids, and antihistamines.
—anaphylactic adj.