Causes

Chronic or recurrent acute sinusitis can be a lifelong condition.

The Role of Bacteria. The role of bacteria or other infectious agents is complicated in chronic sinusitis. They may play a direct, an indirect, or, in some patients, infectious agents may not play any role at all. For example, one study reported the following for patients with chronic sinusitis who had not responded to antibiotics:

• 30% had no evidence of bacteria in their passageways.
• 20% had bacteria unrelated to infection.

Inflammatory Response, Allergies, and Asthma. The absence of bacterial organisms as a causal factor in many cases suggests that some instances of chronic sinusitis may be due to a continuing inflammatory condition. Such on-going inflammation may have been triggered immune factors that were produced in response to injuries from acute sinusitis. Many of the immune factors observed in people with chronic sinusitis resemble those that appear in allergic rhinitis, suggesting that sinusitis in some individuals is due to an allergic response.

Allergies, asthma, and sinusitis often overlap. Those with allergic rhinitis (so-called hay fever and rose fever) often have symptoms of sinusitis, and true sinusitis can develop as a result of the mucus blockage it causes. A causal association, however, has not been proved, and many experts believe allergies themselves rarely predispose to sinusitis. People with chronic sinusitis may also have an allergic reaction to fungal organisms.

Severe asthma (which is often associated with allergies) and chronic sinusitis often overlap, although the relationship is unclear. Between 53 - 75% of children with asthma caused by allergies have sinus abnormalities, and various studies have shown that between 17 - 30% of asthmatic patients develop true sinusitis. In fact, chronic sinusitis may actually be the cause of asthma in some cases.

Abnormalities of the Nasal Passage. Abnormalities in the nasal passage can cause blockage and thereby increase the risk for chronic sinusitis. Some abnormalities include: