Allergic rhinitis, or hay fever, is an immune response to pollen and other microscopic substances. (Pollen is the male component of the plant reproductive system.) The immune system's response to the "invading" pollen causes inflammation and swelling of the lining of the nose and eyelids, triggering hay fever's symptoms, which include sneezing, a runny nose, and itching, watery eyes. Hay fever affects an estimated 1 in 7 Americans and is the country's most common allergic condition.
Fortunately, there are many ways to control hay fever. Avoiding pollen exposure when pollen counts are high, by staying indoors and turning on the air conditioner, helps ease symptoms. Many with this condition also get relief from immunotherapy, or allergy shots, or by taking antihistamines and nasal steroids, among other medications. Moreover, research on hay fever is continuing, and promising new medications are being developed that should be more effective and longer acting than existing drugs.
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The immune system is astoundingly complex and can remember and attack millions of different enemies, from herpes viruses to tapeworms. Unfortunately, many people's immune systems also deploy their resources against harmless substances like peanuts, bee venom, and pollen.
An allergic reaction results from the interplay of three factors:
- The allergen. In the case of hay fever, the allergen is an airborne pollen or mold spore. (Allergic reactions may also be triggered by many other allergens, such as dust mites, latex, animal dander, and certain foods.)
- Mast cells. Although mast cells are found throughout the body, most reside in connective tissues such as those of the skin, tongue, the lining of the nose and intestinal tract, and the lower airways.
- Immunoglobulin E (IgE). IgE is an allergic antibody, a type of protein made by the immune system to recognize and fight specific invaders. IgE coats the surface of the mast cells in tissues.
The first time an allergy-prone person is exposed to an allergen, such as ragweed pollen, special immune cells make large amounts of IgE antibodies specific to that allergen. The antibodies attach themselves to mast cells.
The next time the person is exposed to the allergen, the IgE antibodies recognize it and cause the mast cells to release inflammatory substances, including histamine. These chemicals are what cause the symptoms of allergic rhinitis. For example, histamine permits fluids to enter the nasal tissue, resulting in congestion and a runny nose, and leads to the sensation of itching. These symptoms make good biological sense when the invader is actually dangerous: Sneezing, for example, is a way for the body to expel an invading agent. But when the trigger is pollen, the symptoms merely make for misery.
The following factors are known to increase your risk of developing hay fever:
- You have a family history of allergies.
- You have eczema or asthma.
- You were your parents' firstborn.
Last reviewed on 08/19/2008
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