How fast does an anaphylactic reaction occur in people?

Severe reaction: An anaphylactic reaction is an allergic reaction to a trigger such as a food (peanuts, tree nuts, shellfish) or stinging insect (wasp, honeybee, etc.) that involves multiple body systems at the same time. Thus, you might experience hives/rash (skin), cough/shortness of breath (respiratory), vomithing/diarrhea (gastrointestinal)--these symptoms usually occur within minutes of exposure to a trigger.