Allergy: The perils of overreaction Allergens trick the bodies of some 50 million Americans into attacking a false threat. Normally innocuous airborne matter, such as pollen, mold spores, dander, and dust, can deceive the immune system into generating histamine. Histamine triggers the inflammation of common allergic reactions: runny nose, sneezing, itchy eyes, hives, and rashes. Systemic allergic responses to bee stings, penicillin, latex, and food (shellfish, eggs, peanuts, tree nuts) can lead to severe asthma or anaphylactic shock.