Anaphylaxis Video from YouTube:
An “allergy attack” or allergic reaction can range in severity from an itchy nose to a severe allergic reaction, called “anaphylaxis” which can result in death. An allergic reaction occurs when someone who is allergic to a particularly protein, because he or she has IgE to it in their immune system from previous exposure, is reexposed resulting in release of histamine and other substances.
The severity of the reaction depends on the amount and extent to which histamine is released into the body. A highly peanut allergic person who eats peanuts or someone allergic to bee stings who is stung by a bee can, within a few minutes of exposure, release large amounts of histamine into his skin, lungs, circulatory system, and gastrointestinal tract resulting in hives, throat swelling, airway spasms, dizziness, vomiting, and abdominal spasms, which if untreated, causes generalized organ collapse and death.
A person experiencing anaphylaxis requires emergency medical treatment involving injection of epinephrine.
Source:Asthma and Allergy Foundation of America