The nose is separated into two passages by a wall of cartilage called the septum. The nasal passages are lined with a membrane that produces a clear liquid called mucus. Mucus is a one of the body's defense systems:
- Moisture from the mucus conditions the air before it reaches the lungs.
- The mucus traps small particles and bacteria, which may enter the nose as a person breathes.
- The trapped bacteria usually do not cause harm in healthy individuals.
- When one side of the nose is congested, air passes through the open (decongested) side. The sides normally alternate between being wide-open and partly or completely blocked.
If the congestion becomes severe or other changes occur that irritate the nasal passage, rhinitis develops. Rhinitis is inflammation of the nasal passages. To be diagnosed with rhinitis, a patient must experience at least two of the following symptoms for an hour or more on most days:
- Runny nose
- Nasal congestion
- Nasal itching
|Click the icon to see an image showing symptoms of allergic rhinitis.|
These symptoms may occur as a result of colds or environmental irritants such as allergens, cigarette smoke, chemicals, changes in temperature, stress, exercise, or other factors.
Infectious Rhinitis. If symptoms last fewer than 6 weeks, the condition is referred to as acute rhinitis and is usually caused by a cold or infection, or temporary overexposure to environmental chemicals or pollutants. [For more information, see In-Depth Report #94: Colds and the flu.]
Chronic Rhinitis. When rhinitis lasts for a longer period, the condition is called chronic rhinitis. Allergies are often the cause, but structural problems or chronic infections could also be to blame.
Allergic Rhinitis. Allergic rhinitis is rhinitis caused by allergens, which are substances that trigger an allergic response. Allergens involved in allergic rhinitis come from either outdoor or indoor substances. Outdoor allergens such as pollen or mold spores are usually the cause of seasonal allergic rhinitis (also called hay fever). Indoor allergens such as animal dander or dust mites are common causes of perennial (year-round) allergic rhinitis.
Review Date: 05/03/2011
Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.