Insect Sting Allergic Reactions

Bees, wasps, yellow jackets, hornets, and related insects in the Hymenoptera order inject venom containing allergens. In a sensitized person, venom-specific IgE bound to mast cells and basophils recognizes those allergens and triggers rapid degranulation. Histamine, leukotrienes, and prostaglandins then widen blood vessels, increase capillary leak, constrict bronchial smooth muscle, and stimulate sensory nerves. That mediator release explains the clinical pattern: hives and flushing from skin vasodilation, angioedema from tissue swelling, wheeze from bronchoconstriction, throat tightness or stridor from upper-airway edema, and dizziness or hypotension from reduced effective circulating volume. The same process can affect several systems within minutes. A small local reaction—pain, redness, and swelling confined to the sting site—is not anaphylaxis. A large local reaction is swelling at least 10 cm in diameter around the sting. It may remain uncomfortable and enlarged for more than a day, but by itself carries a low risk of progressing to a systemic reaction. A systemic reaction is the dangerous pattern. After a sting, involvement of at least two organ systems within approximately 5–30 minutes—for example, generalized urticaria plus wheeze—or the development...