Exaggerated immune responses to common airborne fungi seem to be the basic cause of chronically inflamed nasal passages and sinuses in at least some patients with rhinosinusitis, according to a new report.

Although airborne fungal spores enter the airways and lungs when we inhale, the authors explain, they rarely cause illnesses in healthy individuals. Nonetheless, anti-fungal drugs applied to the nasal passages do improve symptoms for many people with chronic rhinosinusitis.

Dr. Hirohito Kita from the Mayo Clinic in Rochester, Minnesota, and colleagues investigated the theory that patients with chronic rhinosinusitis have an exaggerated immune response to common airborne fungi by testing blood specimens and nasal secretions from 18 affected patients and 15 normal individuals.

Less than a third of the rhinosinusitis patients showed anti-fungus antibodies of the type that would indicate an allergic response, the authors report in the Journal of Allergy and Clinical Immunology. However, the participants with chronic rhinosinusitis did have significantly higher blood levels of other antibody types to various fungi than did normal subjects.

Also, blood cells from the affected patients produced more inflammatory factors in response to exposure to fungi than did cells from normal individuals.

The amount of inflammation-promoting substances in nasal secretions also differed markedly between the two groups.

“There is a hypersensitivity response to fungi in patients with chronic sinusitis, which may not be documented by skin prick test,” Kita told Reuters Health.

“We expect that the reduction of fungal exposure will help to reduce the immune response and subsequent inflammation in the sinuses,” the researcher added. “This can be accomplished by environmental control (e.g., less moisture and less fungi in the house) and treatment with anti-fungal agents.”

However, it is not clear if fungus exposure is the culprit in all people with chronic sinusitis, Kita noted. “We still do not know that whether this mechanism operates in 100 percent of patients or only 50 percent of patients.”

SOURCE: Journal of Allergy and Clinical Immunology, October 8, 2004.