Understanding Sinusitis

by National Institute of Health

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, examining your face and forehead, and perhaps doing a sinus X-ray, the doctor says you have sinusitis.

Sinusitis simply means your sinuses are infected or inflamed, but this gives little indication of the misery and pain this condition can cause. Health experts usually divide sinusitis cases into, Acute, which last for 4 weeks or less, Subacute, which lasts 4 to 8 weeks, Chronic, which usually last up to 8 weeks but can continue for months or even years, Recurrent, which are several acute attacks within a year, and may be caused by different organisms

Health experts estimate that 37 million Americans are affected by sinusitis every year. Health care providers report nearly 32 million cases of chronic sinusitis to the Centers for Disease Control and Prevention annually. Americans spend $5.8 billion each year on health care costs related to sinusitis.

What are sinuses?

Sinuses are hollow air spaces 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 sinuses, known as paranasal sinuses. These cavities, located within the skull or bones of the head surrounding the nose, include frontal sinuses over the eyes in the brow area, maxillary sinuses inside each cheekbone, ethmoid sinuses just behind the bridge of the nose and between the eyes, sphenoid sinuses behind the ethmoids 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, an allergic reaction, or another type of immune reaction - also can affect the sinuses. Air trapped within a blocked 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.

Some Causes of Acute Sinusitis

Most cases of acute sinusitis start with a common cold, which is caused by a virus. These viral colds do not cause symptoms of sinusitis, but they do inflame the sinuses. Both the cold and the sinus inflammation usually go away without treatment in 2 weeks. The inflammation, however, might explain why having a cold increases your likelihood of developing acute sinusitis. For example, your nose reacts to an invasion by viruses that cause infections such as the common cold or flu by producing mucus and sending white blood cells to the lining of the nose, which congest and swell the nasal passages.

When this swelling involves the adjacent mucous membranes of your sinuses, air and mucus are trapped behind the narrowed openings of the sinuses. When your sinus openings become too narrow, mucus cannot drain properly. This increase in mucus sets up prime conditions for bacteria to multiply.

Most healthy people harbor bacteria, such as Streptococcus pneumoniae and Haemophilus influenzae , in their upper respiratory tracts with no problems until the body's defenses are weakened or drainage from the sinuses is blocked by a cold or other viral infection. Thus, bacteria that may have been living harmlessly in your nose or throat can multiply and invade your sinuses, causing an acute sinus infection.

Sometimes, fungal infections can cause acute sinusitis. Although fungi are abundant in the environment, they usually are harmless to healthy people because the human body has a natural resistance to fungi. Fungi, such as Aspergillus , can cause serious illness in people whose immune systems are not functioning properly. Some people with fungal sinusitis have an allergic-type reaction to the fungi.

Chronic inflammation of the nasal passages also can lead to sinusitis. If you have allergic rhinitis, also called hay fever, you can develop episodes of acute sinusitis. Vasomotor rhinitis, caused by humidity, cold air, alcohol, perfumes, and other environmental conditions, also may be complicated by sinus infections. (Rhinitis simply means runny nose.)

Acute sinusitis is much more common in some people than in the general population. For example, sinusitis occurs more often in people who have reduced immune function (such as those with primary immune deficiency diseases or HIV infection) and with abnormality of mucus secretion or mucus movement (such as those with cystic fibrosis).

Causes of Chronic Sinusitis

It can be difficult to determine the cause of chronic sinusitis. Some health experts think it is an infectious disease, but others are not certain. It is an inflammatory disease that often occurs in people with asthma. If you have asthma, which is an allergic disease, you may have chronic sinusitis which may make it worse. If you are allergic to airborne allergens, such as house dust mites, mold, and pollen, which trigger allergic rhinitis, you may develop chronic sinusitis. An allergic reaction to certain fungi may be responsible for at least some cases of chronic sinusitis. In addition, people who are allergic to fungi can develop a condition called "allergic fungal sinusitis."

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.