Allergy is a hypersensitivity reaction of the immune system. Allergy may involve more the one type of reaction. An allergy is a immune reaction to something that does not affect most other people. Substances that often cause reactions arePollen, Dust mites, Mold spores, Pet dander, Food, Insect stings, Medicines. Risk factors of allergy are heredity, gender, race, and age.
The immune system is a complex system that normally defends the body against foreign invaders, such as bacteria and viruses, while also surveying for abnormal tissue changes, such as cancer. Allergens are substances that are foreign to the body and that cause an allergic reaction. IgE is the allergic antibody.
The most common allergic diseases are described, including allergic rhinitis (nasal allergies), allergic conjunctivitis (eye allergies), allergic asthma, urticaria (hives), and food allergies. While the environment plays a role in the development of allergy, there is a greater risk of developing allergic conditions if a person has a family history of allergy, especially in parents or siblings.