Allergic rhinitis
Allergic rhinitis is an allergic inflammation of the nasal airways. It occurs when an allergen, such as pollen, dust, Balsam of Peru, or animal dander is inhaled by an individual with a sensitized immune system. In such individuals, the allergen triggers the production of the antibody immunoglobulin E, which binds to mast cells and basophils containing histamine. When caused by pollens of any plants, it is called
pollinosis, and, if specifically caused by grass pollens, it is known as
hay fever. While symptoms resembling a cold or flu can be produced by an allergic reaction to pollen from plants and grasses, including those used to make hay, it does not cause a fever. IgE bound to mast cells are stimulated by allergens, causing the release of inflammatory mediators such as histamine. This usually causes sneezing, itchy and watery eyes, swelling and inflammation of the nasal passages, and an increase in mucus production. Symptoms vary in severity between individuals. Very sensitive individuals can experience hives or other rashes.