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A sneeze in progress.

Sneezing is a trigger for more than saliva expulsion, according to a new study (file picture).

Photograph from CDC/Science Faction/Corbis

Christine Dell'Amore

National Geographic News

Published August 14, 2012

Sure, they blast out germs and other unwanted intruders, but sneezes have another, just discovered purpose, a new study says.

(Get more health news.)

When we breathe in foreign particles, sensors in our noses and sinuses detect the objects. The sensors signal the cilia—tiny, hairlike paddles that line our nostrils and sinuses—to move to expel the irritants.

This process is "always idling at first gear," with the cilia ready to spring into action when needed, said study co-author Noam Cohen, an otolaryngologist—ear, nose, and throat specialist—at the University of Pennsylvania and the Philadelphia VA Medical Center.

The study found that the burst of air produced by a sneeze not only clears nasal passages but also triggers the cilia sensors to kick the paddles into high gear for an extended period—about a couple minutes—Cohen said.

In that sense, a sneeze works by "resetting the system—like Control-Alt-Delete" on a PC, he said.

The study highlights what an "underestimated organ" the nose is, especially in terms of keeping us healthy, added Stella Lee, an otolaryngologist at the University of Pittsburgh School of Medicine.

(Also see "Why Do We Yawn? It May Keep Us From Getting Hot-Headed.")

How They Deconstructed the Sneeze

Cilia—which resemble a "constantly moving shag carpet" under the microscope—propel potentially harmful material out of our lungs and either up to our nostrils to be expelled or down to our gullets, where stomach acid zaps any harmful organisms or particulate matter, Lee said.

For cilia to work, they need mucus—and our nose delivers, producing about a liter (about four cups) a day, most of which we swallow.

People with sinusitis and genetic disorders such as cystic fibrosis have trouble clearing out mucus, even though they sneeze a lot.

The seeming contradiction made Cohen and colleagues wonder whether sneezing has a role in getting cilia to clear out mucus—and whether that process was somehow impaired in sinusitis patients.

The team took cells from the nostrils of healthy people as well as sinusitis patients. The researchers grew the cells in an incubator for several weeks, until the cells formed the same type of lining that's in our sinuses.

The scientists then puffed air on the lining—a sort of "in vitro sneeze"—and "sure enough, we proved the hypothesis. If you puff air on these cells, [their cilia] beat faster," Cohen said. (Explore the human body.)

When the team took tissue from sinusitis patients and puffed air on the tissue, however, the cilia did not beat faster.

"What I think is going on when they sneeze," Cohen said, is that sinusitis patients aren't getting the same cellular response as patients who don't have the syndrome.

For instance, chronic inflammation or toxins in sinusitis-related bacteria may be preventing the cilia from working properly, he said.

Sneeze Study May Benefit Sinusitis Sufferers

The next question, Cohen said, is "Can we actually take this information and translate it into a novel therapy?"

For instance, scientists could theoretically develop nasal sprays or other topical treatments to get the cilia revved up in people with impaired mucus clearance.

The University of Pittsburgh's Lee agreed that the new study "has potential for therapeutic intervention."

There's no "satisfactory treatment option" for chronic sinusitis, which affects an estimated 14 to 16 million Americans, Lee noted. Patients are usually treated with medicine and surgery to relieve the symptoms, which can include congestion, reduced smell and taste, and pain or swelling in the face.

"If we can come up with something that can help this disease," study co-author Cohen added, "it will have a tremendous effect."

The sneezing study was published in the August issue of FASEB Journal.

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