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Causes
By Mayo Clinic staff
When you have sinusitis, the mucous membranes of your nose, sinuses and throat (upper respiratory tract) become swollen. This swelling blocks the sinus openings and prevents mucus from draining normally.
Blocked sinuses create a moist environment that makes it easier for infection to take hold. Sinuses that become infected and can't drain become pus-filled, leading to symptoms such as thick, yellowish or greenish discharge and other symptoms of infection.
Common causes of chronic sinusitis include:
- Nasal polyps or tumors. These tissue growths may block the nasal passages or sinuses.
- Allergic reactions. Allergic triggers include fungal infection of the sinuses.
- Deviated nasal septum. A crooked septum — the wall between the nostrils — may restrict or block sinus passages.
- Trauma to the face. A fractured or broken facial bone may cause obstruction of the sinus passages.
- Other medical conditions. The complications of cystic fibrosis, gastroesophageal reflux, or HIV and other immune system diseases may result in nasal blockage.
- Respiratory tract infections. Infections in your respiratory tract — most commonly, colds — can inflame and thicken your sinus membranes, blocking mucus drainage and creating conditions ripe for growth of bacteria. These infections can be viral, bacterial or fungal in nature.
- Allergies such as hay fever. Inflammation that occurs with allergies may block your sinuses.
- Immune system cells. With certain health conditions, immune cells called eosinophils can cause sinus inflammation.
- Joint Task Force on Practice Parameters for Allergy and Immunology. The diagnosis and management of sinusitis: A practice parameter update. Journal of Allergy and Clinical Immunology. 2005; 116(6)(suppl):13-47.
- Hamilos D, et al. Clinical manifestations, pathophysiology, and diagnosis of chronic rhinosinusitis. http://www.uptodate.com/home/index.html. Accessed Sept. 24, 2008.
- Leung R, et al. The diagnosis and management of acute and chronic sinusitis. Primary Care Clinics. 2008;35:11-24.
- Hamilos D, et al. Management of chronic rhinosinusitis. http://www.uptodate.com/home/index.html. Accessed Sept. 24, 2008.
