Sinusitis is an inflammation of the mucosa (membranes) of the facial sinuses (maxillary, frontal, ethmoid and sphenoid) located in air spaces among bone that surround the nasal passages and eyes. It usually is a bacterial complication of a viral upper respiratory infection.
Usual causes are cold viruses, allergies to various allergens, smoking in any form, bacterial or fungal infections, nasal polyps and deviated nasal septum or non-allergic hypersensitivities. Usual symptoms are increased nasal secretions and pain or headache around the sinuses. Symptoms of acute and chronic sinusitis which occur when the sinuses are inflamed and ostia (outlets) are blocked include nasal congestion, white, yellow, or green discharge, night time cough, pain in the upper jaw or teeth, persistent fatigue, fever, loss of sense of smell or taste, and rarely serious infections like meningitis, brain abscess, ear infections etc.
It is estimated that around 30 to 50 million people suffer from allergic rhinitis and sinusitis.