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Sinus infection? It's the humidity

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That stuffed-up-nose feeling characteristic of a sinus infection may be due to humidity.

If you've ever had a sinus infection, you know how annoying and uncomfortable that plugged-up-nose feeling can be. But there may not actually be anything blocking your nose, says a new study from the Monell Chemical Senses Center, in Philadelpha. That feeling of congestion may be due to the humidity of the air you breathe.

Nasal sinus disease, or sinusitis, affects approximately 33 million people and accounts for more than $5.8 billion in healthcare costs annually, according to a release from Monell. Most of the time, the condition is caused by infection or allergy, which, in turn, causes sinus tissues to swell. That's the can't-get-enough-air feeling that makes a sinus infection so unpleasant. And it's hard to treat, because in many cases, there's nothing really blocking the airways -- no physical obstruction, anyway.

The new study, published today in PLoS One, had 44 healthy volunteers rate their symptoms of stuffiness after breathing air from three boxes. One box contained room air at normal humidity, one held dry air at room temperature and one contained cold air. The volunteers reported feeling less nasal congestion when they breathed from the cold air box and the dry air box, with the cold air being most effective.

Study co-authors Kai Zhao, Ph.D., and co-author Bruce Bryant, Ph.D., both scientists at Monell, theorize that temperature and humidity interact as air moves through the nasal cavity to influence nasal cooling. This cooling is detected by "cool sensors" inside the nose, which can make you feel like it's easy to breathe, or not so much.

“Someone in the desert, all other things being equal, should feel less congested than someone in the jungle. In the low humidity of the desert, there is more evaporative cooling inside of the nose, such that the temperature of the nasal passages is lower. This leads to a feeling of greater air flow – and less sensation of obstruction.” said Bryant in the news release.

Does that mean folks afflicted with a sinus infection should head for the deep freeze to get relief? "From my own experience (probably most sufferers of nasal sinus disease would also agree), immediately after stepping outside during cold winter, I would often feel a brief freshness and clearness of (the nose," wrote Zhao in an e-mail. But prolonged exposure might trigger a nerve reflex, resulting in a runny nose and more congestion. "You can say our study is just scientific confirmation of our obvious daily experiences," added Zhao.

This scientific confirmation could potentially help researchers design and test better treatments for congestion -- good news for for the cloudy-headed. "I do believe understanding what our nose is sensing when we feel nasal obstruction is the initial key step to solving the problem in the future," said Zhao.