|MadSci Network: Immunology|
Hay fever (technically called allergic rhinitis) is the fifth most prevalent chronic condition in the United States with more than 24 million people suffering from it. Hay fever is not caused by contact with hay and does not result in a fever. It is an allergic response to airborne seasonal substances like pollen from weeds, flowers, grasses, and trees, as well as substances like mold, dust mites, animal dander, and tobacco smoke. The vast majority of cases (about 75%) are caused by ragweed pollen (which is produced mainly in the Spring and early summer). Hay fever results when pollen, or another allergen, enters the nasal passage of and reacts with IgE antibodies that are bound to the surface of specialized white blood cells known as mast cells and basophils. With that contact, the cells release chemicals, such as histamine, that produce or control inflammation. These chemicals are responsible for symptoms like itching, watery eyes, sneezing, and coughing. Hay fever is diagnosed most often by presentation of symptoms. The specific cause of hay fever is often diagnosed through a skin test. The test requires a doctor to prick or scratch the skin and apply a small sample of the possible allergen. The area is then monitored for reaction. Newer methods for detecting total IgE (the antibody involved in allergic responses) include enzyme-link immunosorbent assays (ELISA) and the radio allergosorbent technique (RAST). Hay fever can sometimes be treated through avoidance or removal of airborne allergens, if possible (usually only practical with allergies to pets). Over-the-counter and prescription medications are often used to control symptoms. They include antihistamines, decongestants, eye drops, and nasal spray. Immunization with the allergen can help build tolerance to the substance through the production of IgG antibodies. These antibodies react with the allergen before it can bind to the IgE to produce symptoms.
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