Sinusitis refers to inflammation of the sinuses. This is generally caused by a viral, bacterial, or fungal infection.

The sinuses are air-filled spaces in the skull (behind the forehead, cheeks, and eyes) that are lined with mucous membranes. Healthy sinuses are sterile (meaning that they contain no bacteria or other organisms) and open, allowing mucus to drain and air to circulate.

When inflamed, the sinuses become blocked with mucus and can become infected. Each year, over 30 million adults and children get sinusitis.

Sinusitis can be acute (lasting anywhere from 2 - 8 weeks) or chronic, with symptoms lingering much longer.

See also: Chronic sinusitis

Sinusitis can occur from one of these conditions:

• The small openings (ostia) from the sinuses to the nose become blocked.
• Small hairs (cilia) in the sinuses, which help move mucus out, are not working properly.
• Too much mucus is produced.

When the sinus openings become blocked and mucus accumulates, this becomes a great breeding ground for bacteria and other organisms.

Sinusitis usually follows respiratory infections, such as colds, or an allergic reaction. Some people never get sinusitis, and others develop sinusitis frequently.

People more likely to get frequent sinusitis include those with cystic fibrosis and those with immune systems weakened by HIV or chemotherapy.

The following may increase your risk for developing sinusitis:

• Air pollution and smoke
• Asthma
• Changes in altitude (flying or scuba diving)
• Dental work
• Deviated nasal septum, nasal bone spur, or polyp
• Foreign body in your nose
• Frequent swimming or diving
• Gastroesophageal reflux disease (GERD)
• Hospitalization, especially if you are in the hospital because of a head injury or have had a tube placed into your nose (nasogastric tube)
• Overuse of nasal decongestants (rather than continuing to relieve congestion, the problem gets worse when these are used too often or for too long)
• Pregnancy

Cystic fibrosis is one of a number of diseases that prevent the cilia from working properly. Other such diseases that put you at increased risk for sinusitis include Kartagener syndrome and immotile cilia syndrome.

The classic symptoms of acute sinusitis usually follow a cold that does not improve, or one that worsens after 5 - 7 days of symptoms. They include:

• Nasal congestion and discharge
• Sore throat and postnasal drip (fluid dripping down the back of your throat, especially at night or when you lie down)
• Headache -- pressure-like pain, pain behind the eyes, toothache, or facial tenderness
• Cough, often worse at night
• Fever (may be present)
• Bad breath or loss of smell
• Fatigue and generally not feeling well

Symptoms of chronic sinusitis are the same as acute sinusitis, but tend to be milder and last longer than 8 weeks.

Your doctor will test for sinusitis by:

• Tapping over a sinus area; tenderness may indicate infection.
• Shining a light against the sinus (transillumination); if dark, this indicates possible inflammation.

Other tests that might be considered include:

• Viewing the sinuses through a fiberoptic scope
• X-ray of the sinuses
• Cultures of the material from the nose

However, these tests are relatively insensitive for detecting sinusitis, and are often considered unnecessary.

A CT scan of the sinuses is a much better test to help diagnose sinusitis. If sinusitis is thought to involve tumor or fungal infections, an MRI of the sinuses may be necessary.

If you have chronic or recurrent sinusitis, further laboratory evaluation may be necessary to look for an underlying disorder. This may involve sweat chloride tests for cystic fibrosis, ciliary function tests, blood tests for HIV or other tests for immunodeficiency, allergy testing, or nasal cytology (checking the cells in the nasal secretions).