The manifestations of allergy-sneezing, itching, rashes-are signs of an immune system running amok, attacking foreign invaders-allergens-that mean no harm. Allergens include pollen, dust mites, mold, food, drugs, stinging insects, or any other substance to which the body can choose to react, or overreact. Allergies rarely kill. They just make the sufferer miserable-sometimes for brief periods, and sometimes for life.