Updated 15 July 2014

Causes of sinusitis

Anything interfering with airflow into and drainage of mucus out of the sinuses can cause sinusitis.

•    Anything interfering with airflow into and drainage of mucus out of the sinuses can cause sinusitis.
•    The sinus openings may be obstructed by anything, causing swelling of tissue lining the ostia and adjacent nasal passage, such as colds, allergies and tissue irritants (such as over-the-counter nasal sprays, cigarette smoke and recreational substances snorted through the nose).
•    Allergies may complicate sinusitis.
•    Drainage of mucus can be impaired by thickening of secretions, decrease in mucus hydration (water content) because of disease, drying medications (antihistamines), and lack of air humidity.
•    Irritants, especially smoke, may damage cilia, and prevent them from assisting with mucus drainage. Stagnated mucus provides an ideal environment for bacteria and in some cases (such as AIDS) fungus to grow.
•    Other irritants include car exhaust, petrol and paint fumes, perfume, insect spray and household chemicals.
•    Sinuses can become obstructed by tumours or growths. Nasal polyps (growths arising from mucous surfaces), probably caused by nasal inflammation, can block the ostia.
•    Occasionally, immune problems cause sinus infections. If you have persistent sinus infections, have your immune system evaluated by an allergist/immunologist, especially before surgery is done. You may need allergy tests, and tests to ensure you can form antibodies to common bacteria normally. Sinusitis can be due to AIDS, although only an extremely small percentage of people with sinusitis have AIDS.

Risk factors

•    People with allergies (which cause nasal congestion) are at higher risk of developing sinus headaches and sinusitis.
•    Smokers (tobacco smoke irritates the nasal passages and lowers the body's natural resistance) are also prone to sinusitis.
•    People in professions where they are often exposed to infection, such as health care workers, are most likely to get sinusitis.
•    Certain anatomical variations, such as a deviated nasal septum, or abnormal turbinates, may make the ostia vulnerable and the patient more susceptible to obstruction of the ostia and result in sinusitis.

When to see a doctor

Although rare, serious complications can result from sinus infections. These include direct extension of infection to the brain and eyes, and blockage of vessels in the head. Erosion of bone can occur if infection eats through the sinuses. Untreated sinusitis can lead to acute bronchitis, ear infection and pneumonia. In certain cases, medical attention is needed.

Call your doctor if:

•    Cold symptoms last longer than 10 to 14 days or worsen over time.
•    You have a severe headache that is not relieved by acetaminophen, aspirin, or ibuprofen or a decongestant.
•    There is increased facial swelling, or changes in vision.
•    Nasal discharge changes from clear to yellow or green after five to seven days of a cold, and other symptoms (such as sinus pain or fever) are worsening. If nasal discharge is coloured from the start of a cold, call if it lasts longer than 7 to 10 days.
•    Facial pain, especially in one sinus area or along the ridge between the nose and lower eyelid, persists after 2 to 4 days of home treatment. If you also have a fever and coloured nasal discharge, call in 1 to 2 days.
•    Sinusitis symptoms persist after a full course of antibiotics.

 (Updated by Dr H Steinman, June 2007)


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