∞ generated and posted on 2016.01.10 ∞
Allergic reaction that is both substantial, including to the point of being lethal, and rapid in onset.
Allergic reactions can be to insect bites, various foods, and drugs, e.g., bee stings, nut allergies, and penicillin allergies. The signs and symptoms of anaphylaxis are treatable via injection of the hormone, epinephrine.
See also anaphylactic shock (see too here).