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Anaphylaxis (say "ann-uh-fuh-LAK-suss") is a severe allergic reaction that affects the entire
body (systemic). It can occur within a few seconds or minutes after a person is
exposed to a substance (allergen or antigen).
Symptoms and signs of a severe allergic reaction may
The sooner symptoms occur after exposure to the substance, the more
severe the anaphylactic reaction is likely to be. An anaphylactic reaction may
occur with the first exposure to an allergen, with every exposure, or after
several exposures. An anaphylactic reaction can be life-threatening and is a
medical emergency. Emergency care is always needed for an anaphylactic
Current as of:
February 20, 2015
William H. Blahd, Jr., MD, FACEP - Emergency Medicine & H. Michael O'Connor, MD - Emergency Medicine
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