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Sinusitis Cause

Colds, bacterial infections, allergies, asthma, and other health conditions can cause sinusitis, or inflammation of the paranasal sinuses.

Acute Sinusitis

Acute sinusitis is usually caused by a viral or bacterial infection. The common cold, which is caused by a virus, may lead to swelling of the sinuses, trapping air and mucus behind the narrowed sinus openings. Both the nasal and the sinus symptoms usually go away within two weeks. Sometimes, viral infections are followed by bacterial infections. Many cases of acute sinusitis are caused by bacteria that frequently colonize the nose and throat, such as Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. These bacteria typically do not cause problems in healthy people, but in some cases they begin to multiply in the sinuses, causing acute sinusitis. NIAID supports studies to better understand what factors put people at risk for bacterial sinusitis. For example, an NIAID-supported clinical trial is investigating relationships between viral respiratory infections, changes in the microbial communities in the nose and throat, and the risk of acute bacterial sinusitis in children.

People who have allergies or other chronic nasal problems are prone to episodes of acute sinusitis. In general, people who have reduced immune function, such as those with HIV infection, are more likely to have sinusitis. Sinusitis also is common in people who have abnormal mucus secretion or mucus movement, such as people with cystic fibrosis, an inherited disease in which thick and sticky mucus clogs the lungs.

Chronic Sinusitis or Rhinosinusitis

In chronic sinusitis, also known as chronic rhinosinusitis, the membranes of both the paranasal sinuses and the nose thicken because they are constantly inflamed. This condition can occur with or without nasal polyps, grape-like growths on the mucous membranes that protrude into the sinuses or nasal passages. The causes of chronic rhinosinusitis are largely unknown. NIAID supports basic research to help explain why people develop this chronic inflammation.

People with asthma and allergies, recurrent acute sinusitis, and other health conditions are at higher risk of developing chronic rhinosinusitis. In fact, some evidence suggests that chronic rhinosinusitis and asthma may be the same disease occurring in the upper and lower parts of the respiratory system, respectively. NIAID supports research to understand the causes of chronic airway inflammation in asthma and its link to chronic rhinosinusitis. For example, NIAID-supported researchers are investigating aspirin-exacerbated respiratory disease (AERD), a condition in which people have asthma and chronic rhinosinusitis with nasal polyps and experience potentially severe respiratory reactions to aspirin and other nonsteroidal anti-inflammatory drugs. Researchers are investigating the basic mechanisms of disease in these people, as well as developing ways to improve treatment. Other groups of NIAID-supported researchers are examining whether viral infections cause worsening of chronic rhinosinusitis and identifying differences in genes and proteins in people with chronic rhinosinusitis and those whose sinuses are healthy.​

Last Updated May 15, 2015