Chronic sinusitis is swelling of the sinuses, usually caused by an infection. Common causes and risk factors include upper respiratory tract infections, allergies, nasal polyps, deviated nasal septum, smoking and having a weakened immune system.

Chronic sinusitis occurs when symptoms last for longer than 12 weeks. Structural abnormalities can sometimes be seen on x-rays or CT scans and in some cases, surgery is required to relieve symptoms.