An allergic reaction occurs when the immune system mistakenly identifies a normally harmless substance as a dangerous invader. The immune system then produces antibodies that actively seek out that particular allergen. When exposed to the allergen again, these antibodies can release a number of immune system chemicals that cause allergy symptoms, such as runny nose, sneezing, itchy eyes, watery eyes, rash, and swelling. Common allergy triggers include: • Airborne allergens, such as: • pollen • animal dander • dust mites • mold • Certain foods, particularly: • peanuts • tree nuts • wheat • soy • fish • shellfish • eggs • milk • Insect stings or bites, including: • bee stings • wasp stings • spider bites • fire ant stings • mosquito bites • bedbug bites • flea bites • Medications, particularly: • penicillin • penicillin-based antibiotics • Latex or other substances