IMMUNOLOGY

Detailed explanation-1: -Hypersensitivity reactions are exaggerated or inappropriate immunologic responses occurring in response to an antigen or allergen. Type I, II and III hypersensitivity reactions are known as immediate hypersensitivity reactions because they occur within 24 hours of exposure to the antigen or allergen.

Detailed explanation-2: -Allergic reactions start in your immune system. If you are allergic to a substance such as dust, mold, or pollen and you come into contact with it, your immune system may overreact. It may make antibodies that attack the substance.

Detailed explanation-3: -Allergic reactions (hypersensitivity reactions) are inappropriate responses of the immune system to a normally harmless substance. Usually, allergies cause sneezing, watery and itchy eyes, a runny nose, itchy skin, and rash. Some allergic reactions, called anaphylactic reactions.

Detailed explanation-4: -Allergy occurs when a person reacts to substances in the environment that are harmless to most people. These substances are known as allergens. Allergens are found in dust mites, pets, pollen, insects, ticks, moulds, foods and some medications.