Causes of sinusitis

Sinusitis is inflammation of the lining of the sinuses, the air-filled spaces in the bones around the nose, cheeks and forehead. Normally the sinuses drain mucus into the nose through small openings. When these openings swell or get blocked, mucus is trapped and germs can grow, leading to pain, pressure and congestion.

Main causes

• Viral infection: the common cold is the most frequent trigger. Most acute sinusitis is viral and clears on its own.
• Bacterial infection: sometimes follows a cold, when trapped mucus becomes infected.
• Fungal infection: uncommon, usually in people with weak immunity or diabetes.
• Allergies such as hay fever, which cause nasal swelling.

Structural problems

• Deviated nasal septum.
• Nasal polyps (soft growths in the nose lining).
• Enlarged adenoids in children.
• Narrow drainage channels.

Triggers and risk factors

• Smoking and exposure to smoke, dust, fumes and air pollution.
• Dry air, or sudden changes in temperature.
• Swimming or diving in dirty water.