Allergy is a disorder of the immune system which is a form of hypersensitivity. [1] Allergic reactions occur to normally harmless environmental substances known as allergens ... The most comprehensive Allergy resources at ClinicAllergy.comGet the facts about allergic reactions, causes, allergy types (food, dust, mold, seasonal), symptoms and signs (skin rash, itching, red bumps, sneezing). The most comprehensive Allergy resources at ClinicAllergy.comAn allergy is a reaction of your immune system to something that does not bother most other people. People who have allergies often are sensitive to more than one thing. The most comprehensive Allergy resources at ClinicAllergy.comallergy n. , pl. , -gies . An abnormally high sensitivity to certain substances, such as pollens, foods, or microorganisms The most comprehensive Allergy resources at ClinicAllergy.com