Definition of Allergic rhinitis:

Allergic rhinitis is a collection of symptoms, mostly in the nose and eyes, which occur when you breathe in something you are allergic to, such as dust, dander, or pollen.

This article focuses on allergic rhinitis due to outdoor triggers, such as plant pollen. This type of allergic rhinitis is commonly called hay fever.

For information on other types of allergies, see:

• Allergies
• Allergy to mold, dander, dust
• Asthma

Causes, incidence, and risk factors:

An allergen is something that triggers an allergy. When a person with allergic rhinitis breathes in an allergen such as pollen or dust, the body releases chemicals, including histamine. This causes allergy symptoms such as itching, swelling, and mucus production.

Hay fever involves an allergic reaction to pollen. (A similar reaction occurs with allergy to mold, animal dander, dust, and similar inhaled allergens.)

The pollens that cause hay fever vary from person to person and from region to region. Tiny, hard to see pollens more often cause hay fever. Examples of plants commonly responsible for hay fever include:

• Trees (deciduous and evergreen)
• Grasses
• Ragweed

The amount of pollen in the air can play a role in whether hay fever symptoms develop. Hot, dry, windy days are more likely to have increased amounts of pollen in the air than cool, damp, rainy days when most pollen is washed to the ground.

Some disorders may be associated with allergies. These include eczema and asthma.

Allergies are common. Your genes and environment may make you more prone to allergies.

Whether or not you are likely to develop allergies is often passed down through families. If both your parents have allergies, you are likely to have allergies. The chance is greater if your mother has allergies.