Sinusitis is an inflammation of the paranasal sinuses.
Under normal circumstances, the sinuses produce a scanty amount of mucoid fluid, however, when inflammation sets in, as a result of allergy or a common cold, the mucosal lining produces a profuse mucoid drainage. Inflammation makes it easier for bacteria to infect the sinuses. As a result, pus accumulates inside the sinus cavities. Symptoms consist of severe pain and tenderness over the involved sinus. In maxillary sinusitis, pain is over the cheek and the upper teeth. Frequently, the pain is mistaken for that of an infected tooth. In ethmoid sinusitis, the pain is between the eye and the nose, or deep behind the eye. In frontal sinusitis, the pain is in the forehead. Finally, in sphenoid sinusitis, the pain is deep behind the eye, in the temple or even the crown of the head. Discharge from the nose may be blood-tinged and rapidly becomes almost pure pus. The nose is blocked and the throat becomes inflamed because of the post-nasal drainage. If the orifices of the sinuses are blocked by a swollen mucosal lining, pus cannot escape into the nose and builds up pressure inside the sinus cavities. Pain becomes unbearable, and the infection may extend outside the walls of the sinuses, causing facial or orbital swelling.