Allergy also known as hypersensitivity is a condition in which the immune system reacts abnormally to a foreign substance (allergen). Common types of allergies include drug allergy, food allergy, contact dermatitis, Latex allergy, allergic asthma, allergic rhinitis, animal allergy, mold allergy and anaphylaxis. Out of all the above anaphylaxis is a severe and potentially life-threatening form of hypersensitivity reaction. Treatment includes antihistamines, corticosteroids, decongestants, leukotriene modifiers and Immunotherapy.