Chronic sinusitis is a long-term inflammation of the sinuses. The sinuses are moist air spaces behind the bones of the upper face — between the eyes and behind the forehead, nose and cheeks. Normally, the sinuses drain through small openings into the inside of the nose. Anything that obstructs that flow can cause a buildup of mucus, and sometimes pus, in the sinuses. Drainage from the sinuses can be obstructed by structural abnormalities of the nose, infection, or tissue swelling caused by allergies. The buildup of mucus leads to increased sinus pressure and facial pain. In adults, chronic sinusitis most often is linked to nasal swelling caused by allergies, especially allergies to inhaled dust, mold, pollen, or the spores of fungi. These allergies trigger the release of histamine and other chemicals that cause the inner lining of the nose to swell and block sinus drainage.
Polyps, nasal tumors and nasal fractures can obstruct the sinus drainage leading to chronic sinusitis. Chronic sinusitis also can be seen in people whose sinuses and nasal passages are structurally abnormally narrow. People with asthma, cystic fibrosis, or immune system problems develop chronic sinusitis more often than others.