acute or chronic inflammation of the mucosal lining of one or more paranasal sinuses (the cavities in the bones that adjoin the nose). Sinusitis commonly accompanies upper respiratory viral infections and in most cases requires no treatment. Purulent (pus-producing) sinusitis can occur, however, requiring treatment with antibiotics. Chronic cases caused by irritants in the environment or by impaired immune systems may require more extended treatment, including surgery.

The origin of acute sinus infection is much like that of ear infection (see otitis media). Normally the middle ear and the sinuses are sterile, but the adjacent mouth and nose have a varied bacterial flora. Under normal conditions, very small hairs called cilia (cilium) move mucus along the lining of the nose and respiratory tract, keeping the sinuses clean. When ciliary function is damaged, infection can be established. Following a common cold, a decrease in ciliary function may permit bacteria to remain on the mucous membrane surfaces within the sinuses and to produce a purulent sinusitis. The organisms usually involved are Haemophilus influenzae, Streptococcus pneumoniae, staphylococcus aureus, Streptococcus pyogenes, and many other penicillin-sensitive anaerobes. Common symptoms include facial pain, headache, and fever following previous upper respiratory viral illness. On physical examination, persons with sinusitis are usually found to have an elevation in body temperature, nasal discharge, and sinus tenderness. Diagnosis can be confirmed by X-rays of the sinuses and cultures of material obtained from within the sinuses.

Treatment of acute sinusitis is directed primarily at overcoming the infecting organism by the use of systemic antibiotics (antibiotic) such as penicillin and at encouraging drainage of the sinuses by the use of vasoconstricting nose drops and inhalations. If the infection persists, the pus localized in any individual sinus may have to be removed by means of a minor surgical procedure known as lavage, in which the maxillary or sphenoidal sinuses are irrigated with water or a saline solution.

Chronic sinusitis may follow repeated or neglected attacks of acute sinusitis, particularly if there is impaired breathing or drainage due to nasal polyps or obstructed sinus openings. It may also be caused by allergy to agents in the environment, such as fungi or pollen. The symptoms of chronic sinusitis are a tendency to colds, purulent nasal discharge, obstructed breathing, loss of smell, and sometimes headache. Pain is not a feature of chronic sinusitis. If antibiotic therapy or repeated lavage do not alleviate the condition, steroidal medications may be given to relieve swelling and antihistamines to relieve allergic reactions. In severe cases endoscopic surgery may be necessary to remove obstructions.