You're coughing and sneezing and tired and achy. You think that you might be getting a cold. Later, when the medicines you've been taking to relieve the symptoms of the common cold are not working and you've now got a terrible headache, you finally drag yourself to the doctor. After listening to your history of symptoms and perhaps doing a sinus X-ray, the doctor says you have sinusitis.

Sinusitis simply means inflammation of the sinuses, but this gives little indication of the misery and pain this condition can cause. Chronic sinusitis -- sinusitis that recurs frequently -- affects an estimated 32 million people in the United States. Americans spend millions of dollars each year for medications that promise relief from their sinus symptoms.

Sinuses are hollow air spaces, of which there are many in the human body. When people say, "I'm having a sinus attack," they usually are referring to symptoms in one or more of four pairs of cavities, or spaces, known as paranasal sinuses.

These cavities, located within the skull or bones of the head surrounding the nose, include the frontal sinuses over the eyes in the brow area, the maxillary sinuses inside each cheekbone, the ethmoids just behind the bridge of the nose and between the eyes, and behind them, the sphenoids in the upper region of the nose and behind the eyes.

Each sinus has an opening into the nose for the free exchange of air and mucus, and each is joined with the nasal passages by a continuous mucous membrane lining. Therefore, anything that causes a swelling in the nose -- an infection or an allergic reaction -- also can affect the sinuses.

Air trapped within an obstructed sinus, along with pus or other secretions, may cause pressure on the sinus wall. The result is the sometimes intense pain of a sinus attack. Similarly, when air is prevented from entering a paranasal sinus by a swollen membrane at the opening, a vacuum can be created that also causes pain.

Sinusitis has its own localized pain signals, depending upon the particular sinus affected. Headache upon awakening in the morning is characteristic of sinus involvement. Pain when the forehead over the frontal sinuses is touched may indicate inflammation of the frontal sinuses.

Infection in the maxillary sinuses can cause the upper jaw and teeth to ache and the cheeks to become tender to the touch.

Since the ethmoid sinuses are near the tear ducts in the corner of the eyes, inflammation of these cavities often causes swelling of the eyelids and tissues around the eyes and pain between the eyes. Ethmoid inflammation also can cause tenderness when the sides of the nose are touched, a loss of smell, and a stuffy nose.

Although the sphenoid sinuses are less frequently affected, infection in this area can cause earaches, neck pain, and deep aching at the top of the head.

Other symptoms of sinusitis can include fever, weakness, tiredness, a cough that may be more severe at night, and runny nose or nasal congestion. In addition, drainage of mucus from the sphenoids down the back of the throat (postnasal drip) can cause a sore throat and can irritate the membranes lining the larynx (upper windpipe).

(The information about sinusitus on our site is taken from a publication prepared by the National Institute of Allergy and Infectious Diseases (NIAID), a component of the National Institutes of Health. NIAID supports research on AIDS, tuberculosis and other infectious diseases as well as allergies and immunology.)