When most people are stung by an insect, the site of the sting develops redness, swelling and itching. However, when people are allergic to insect stings, their immune system overreacts to the venom by producing allergic antibodies called immunoglobulin E (IgE). This triggers the release of substances including histamine that then cause an allergic reaction.
For some people, especially adults, stings may be life threatening and can result in anaphylaxis. The symptoms of a severe allergic reaction may include itching and hives, swelling in the throat or tongue, difficulty breathing, dizziness, stomach cramps, nausea or diarrhea.