Sinus infections afflict 37 million Americans, causing everything from runny noses to chronic congestion. When the mucus lining in the sinuses is exposed to a fungus, it becomes irritated and swollen. The swelling doesn't allow the sinuses to drain properly.
"Up to now, the cause of chronic sinusitis has not been known," Mayo Clinic researchers said, based on their report appearing in the journal, Mayo Clinic Proceedings.
"Fungus allergy was thought to be involved in less than 10 percent of cases. Our studies indicate that, in fact, fungus is likely the cause of nearly all of these problems. And it is not an allergic reaction, but an immune reaction," researchers David Sherris, Eugene Kern and Jens Ponikau said.
The researchers are working with pharmaceutical companies to set up trials to test medications to control the fungi, but they estimated that it will be at least two years before any treatments are available.
"Anything that causes inflammation in the lining of the sinuses makes someone vulnerable to a sinus infection," explains ear, nose, and throat specialist Dr. Karin Evan.
To draw their conclusions, they used a new method to test the mucus of 210 patients with chronic sinusitis and discovered fungus in 96 percent of the patients. They identified 40 different kinds of fungi in the mucus, with patients having an average of 2.7 varieties each.
There are thousands of kinds of single-cell molds and yeasts found around the world and their spores become airborne. One example is pollen.
In nearly all of a subset of 101 patients who underwent surgery to remove nasal polyps, which are small growths in the nasal passages that can hinder breathing, the researchers found a type of white blood cell activated by the immune system called eosinophils.
The eosinophils are sent by the immune system to attack the fungi, but also irritate the membranes of the nose.
In contrast to chronic sinusitis that persists for three months or longer and afflicts suffers with a runny nose and headaches and can cause a loss of the sense of smell, acute sinusitis lasts a month or less and is usually caused by a bacterial infection, they said.
Antibiotics widely used to treat both conditions are ineffective against the chronic form caused by fungi. Many sufferers also take decongestants to relieve the symptoms but these medications have no effect on the inflammation.
"This study has helped direct our research into treatment for chronic sinusitis in the right direction," Dr. Sherris explains. "Hopefully, in the next few years, we'll have something that we can deliver to patients."
While a cure is not yet available, doctors suggest patients continue to use antihistamines and nasal steroid sprays to treat thsymptoms of chronic sinusitis.