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Updated May 03, 2008


Anaphylaxis is a full-body allergic reaction caused by the release of histamine dilating the blood vessels and causing swelling throughout the body. The histamine release can cause a number of effects in the body, the most serious including obstruction of the airways; a sudden, dramatic drop in blood pressure; and shock.

Anaphylaxis is always a medical emergency, and can be fatal if untreated.

Also Known As: Anaphylactic shock
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