Normal Sinus Function
The sinuses are cavities within the cheek bones, around the eyes and behind the nose. Although their precise function is not known, it has been suggested that they play an important role in warming, moistening and filtering the air in the nasal cavity, resonating vocalized sound, and keeping the weight of the skull at a manageable level. One thing is true, the sinuses are constantly at risk of attack from viruses, bacteria, and mold looking to move into the warm, dark, moist, and nutritious environment of the sinus cavity.

The sinuses primary defense against invasion is drainage. Seen under the microscope the sinuses are lined with a tall cell with waving, hair like projections called cilia. There are also numerous mucous glands that provide a constant layer of mucous that is kept in motion by the sweeping cilia. The mucous moves in a coordinated manner around the sinus lining eventually being swept out of small openings in the sinus called the ostia. The sinus ostia are located under wing-like bony structures in the nasal passage called the turbinates. Mucous draining from the sinus ostia is directed backwards toward the throat were it is swallowed. Normal sinus drainage occurs throughout the day and usually goes unnoticed. When the amount of the mucous increases significantly or the character of the mucous changes we may experience it as post nasal drainage.

The coordinated flow of mucous is critical to the health of the sinuses. The mucous not only contains enzymes and antibodies that kill specific pathogens, but the constant tide of flowing mucous prevents viruses and bacteria from infecting the cells lining the sinus causing disease. Oxygen is toxic to many harmful bacteria but necessary for the health of cilia. It is therefore important that the sinuses remain open to the air. When the sinus ostia become plugged – as can occur with allergy, anatomical narrowing or polyps- the mucous becomes thick and stagnant, the oxygen level in the sinus drops, the cilia cannot function normally and bacteria are given an opportunity to grow and cause infection To fight back the sinuses will try to flush out the invaders by producing more mucous. Without proper drainage, however, it is a difficult fight to win. As a secondary defense measure, the lining of the sinus may become thickened.

Inflammation of the sinuses is called sinusitis. This inflammation may be the result of infection, injury, and allergy and can be acute or chronic.

Acute sinusitis is characterized by symptoms lasting less than 4-6 weeks and is usually caused by infection. Symptoms of acute sinusitis are familiar and include pressure around the nose, eyes or forehead, stuffy nose, thick, discolored nasal drainage, post-nasal drip, cough, head congestion, and ear fullness. Some patients with acute sinusitis may also complain of a toothache and occasionally fever.

Acute sinus infections may be caused by viruses or bacteria. The common cold virus frequently infects the sinuses resulting in sinus pressure, discolored nasal discharge, and post nasal drainage. These symptoms will typically begin to improve after 5-7 days without treatment. When symptoms persist beyond a week, or worsen suddenly, it is often because a bacteria has moved in, taking advantage of the weakened condition of the sinuses caused by the cold virus. For many doctors and patients the term “sinus infection” refers to a bacterial infection of the sinus requiring an antibiotic. Because even the best doctor cannot tell the difference between a viral and a bacterial infection based on history of physical exam alone, it may be appropriate to reserve antibiotics for symptoms that have lasted 7-10 days without improvement.

Inflammation of the sinuses lasting for more than 4-6 weeks is called chronic sinusitis. The symptoms of chronic sinusitis may be subtle and limited to recurrent post nasal drainage, frequent throat clearing, recurrent cough, nasal congestion, poor sense of taste or smell, and stuffy ears. The cause of chronic sinusitis may be a bacterial infection that the body has not been able to completely clear, reaching a kind of “stale mate”: the infection is not progressing but the body isn’t getting rid of it either. As a result of the persistent infection, the lining of the sinus may become thickened and drainage less efficient. It is theorized that in some cases a bacterial infection will injure the lining of the sinuses to such a degree that even when the infection is eradicated, poorly functioning cilia, thickened sinus membranes, and inefficient drainage persists.

Some types and mold may find there way into the sinus cavities and begin to grow. Some researches feel that mold in the sinuses is an important causes of chronic sinusitis. Others feel that chronic sinusitis presents an opportunity for fungus to grow, and is therefore an innocent bystander in the disease process. Some mold varieties are highly allergenic and if you are allergic to mold that is growing in the sinuses, symptoms of severe sinusitis and asthma may develop.

Allergies to air-born allergens such as pollen, mold, and animal dander may increase the risk for developing sinusitis because allergies can cause swelling of the nasal tissues limiting normal sinus function. The sneezing, sniffling, and nasal congestion associated with hay fever may increase the chance of bacteria in the nasal cavity finding it’s way into the sinuses.

Management of allergy symptoms with medications and immunotherapy may reduce the likelihood of developing an infection.

In rare cases, immune problems that limit the bodies ability to fight common infections may present with chronic or recurrent sinusitis.

Structural abnormalities of the nasal cavity, such as narrow sinus ostia, tumors or a shifted nasal septum (the bone and cartilage that separate the right from the left nostrils), may also cause sinusitis. If the problem is structural then surgical correction may be curative, however, because many patients with recurring or chronic sinusitis have more than one factor that puts them at risk of infection. a proper evaluation and accurate diagnosis is essential. You cannot fix an allergy problem with surgery.

Sinusitis in a Desert Environment

Living in Phoenix presents unique problems for the sinuses. The sinuses need a constant flow of mucous to stay healthy. Individuals who grew up in a humid environment like Chicago, Portland, or Atlanta and then move to Ahwatukee, Chandler, or Maricopa, may suddenly find that the dry climate of their new home does not provide enough moisture to keep the sinuses functioning as usual. Like the excessive tearing associated with chronic dry eyes, the sinuses may respond to the dry conditions by producing too much mucous, leading to post nasal drip syndrome. In addition, the amount of suspended fine particles in the air such as quartz and diesel particles, is greater in the desert, and when breathed can damage the lining of the nose, sinuses, and airways leading to tissue injury and chronic inflammation. The inflaming effect of particulates and other air pollutants may heighten the effect of air-born pollen and mold. The result if more severe allergies, asthma, and sinus problems.

Sinusitis Versus Rhinitis

Symptoms of sinusitis and rhinitis are very similar. Rhinitis is a swelling of the mucous membranes of the nose while sinusitis includes swelling of the sinuses in addition to the nasal passages. For this reason, sinusitis is often called rhino-sinusitis.

Rhinitis may be allergic or non-allergic. Symptoms of allergic rhinitis often are a runny nose, sneezing, nasal congestion and itchy eyes, nose, throat and ears. People with non-allergic rhinitis may have a very stuffy or a very runny nose. It may be caused by irritants such as air pollution, dryness, smoke, changes in barometric pressure or temperature or overuse of over-the-counter decongestant nasal sprays.


The evaluation of sinusitis should include a detailed history and physical examination. Allergy testing is needed to differentiate allergic from non-allergic rhino-sinusitis. A sinus CT scan may be needed to look for evidence of infection or structural abnormalities. If in doubt, tests to insure that the immune system is in proper working order may be ordered.


Acute bacterial sinus infections are treated with antibiotics and if needed, agents to reduce inflammation and promote drainage Chronic sinusitis can be a challenge to treat for a number of reasons. The inflammation in chronic sinusitis is similar to that seen in chronic asthma. Although the inflammation is asthma is routinely treated successfully with inhaled steroids, we do not have a way to get topical steroids into the sinuses. In fact, the nasal passage and turbinates are designed to keep things from entering the sinuses from the nose. So although nasal steroids are frequently used to reduce nasal congestion, very little makes it into the sinuses. Oral steroids, can provide significant improvement in sinus symptoms but have significant side effects if taken for more than 1-2 weeks. Antihistamines are not helpful in chronic sinusitis for the same reason that they are not helpful in chronic asthma: the inflammation involves many different cells and chemicals besides histamine. Several non-drug treatments can be helpful including breathing warm, moist air and irrigating the nasal cavities with salt water.

For people with allergies, long-term treatment to control and reduce nasal congestion and other allergic symptoms can help in preventing sinusitis.