Allergic rhinitis is the set of symptoms that occurs when you breathe in substances you are allergic to. These substances are called allergens and are small proteins.

  • Seasonal (intermittent) allergic rhinitis (sometimes called hay fever or rose fever)—This occurs during times of the year when allergens are in the air, like spring, summer, and fall. The most common allergens are tree, grass, or weed pollens.
  • Perennial (persistent) allergic rhinitis—This condition is caused by allergens that may be present year round. These may include chemicals, dust, dust mites, cockroaches, animal dander, or mold spores. Symptoms may be present any time of year.

An allergic reaction occurs when your body's immune system overreacts to an allergen. When you breathe in an allergen, cells in your nasal passages release a chemical called histamine. Histamine causes your nose to feel itchy. Histamine also causes swelling and mucus production in the nasal passages.

Site of Histamine Production
Nasal passage
This area has swelling and increased mucus production after contact with an allergen.
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