Allergic rhinitis, commonly referred to as hay fever, is a very common condition affecting more than 20% of people living in the United States. Allergic rhinitis is caused by exposure to substances in the air called allergens. Allergens are usually harmless substances, such as pollen, dust mites, pet dander or mold that the immune system typically ignores. However, in people with allergic rhinitis, the immune system mistakenly identifies these allergens as ‘intruders’ and generates a reaction against them.
In allergic individuals, the immune system produces a specific type of antibody call IgE (the ‘allergy antibody’) against the allergen (e.g. cat dander). The IgE antibody coats immune cells called mast cells. Mast cells exist everywhere the body comes in contact with the outside environment (the skin, respiratory tract, gastrointestinal tract) and contain a number of chemicals , such as histamine, that cause allergic symptoms. On exposure to an allergen, the IgE molecules bind to it and this triggers the mast cell to burst and release its histamine and other chemicals.