Allergy is a condition caused by the immune system’s hypersensitivity to something in the environment that normally causes little or no trouble to other people. Common allergens are certain food items, dust, pollen, insect bites, and certain medications. Allergens can be inhaled (pollen, dust, mold, fungi, animal dander), eaten (egg whites, milk, nuts, shrimp, fish, wheat, or rice), injected (bee stings or medications), or exposed to the skin. or eyes (dust, pollen, animal dander, mold).
Sensitivity to allergens can be caused by both genetic and environmental factors. When a person is exposed to an allergen, immunoglobulin-E antibodies (IgE) in the person’s body bind to the allergen and deliver it to receptors called basophils. This triggers the release of inflammatory chemicals such as histamine that cause reactions such as inflammation, itching, sneezing, runny nose, red eyes, and difficulty breathing.