

As the old joke goes, "If your nose runs, and your feet smell, you're built upside down!" Kidding aside, there are many reasons we get runny noses — technically known as rhinorrhea. When you have a cold or the flu, the mucous membranes that line the cavities in your nose produce a combination of mucus and fluid designed to fight off and wash away the germs. The nose also produces extra mucus after exposure to an allergen , whether it's pollen, animal dander, or something else. Crying hard can also cause excess liquid to drain from the duct in the inner corner of the eyelid into the nasal cavities and out through the nose.

But why does your nose run when you're out on a chilly winter day, even when you're not sick or upset?

Your Nose at Work

Our noses warm and humidify — add moisture to — the air we breathe as it travels down into the lungs. So when you inhale cold, dry air, the moist tissue inside the nose automatically increases fluid production to do its job of protecting sensitive lung tissue. But when there's too much fluid, the excess tends to drip out, creating a runny nose.

Winter has other effects that make it more likely you’ll have a runny nose. Cold temperatures can cause the small water droplets inside the moist nose to join together, forming big, heavy drops of water that can also drip from your nostrils. And cold air also speeds up mucus production.

Could You Have Skier’s Nose?

Researchers have a name for a related syndrome linked to exercising outdoors in cold weather: Not surprisingly, it's called skier's nose. A 1991 study published in the journal Annals of Allergy, Asthma and Immunology found that nearly 100 percent of skiers complained about runny noses while participating in their sport.

While a runny nose is annoying in just about any season, it's not harmful. And if you're worried that you'll get a cold from being out in the cold, don't fret. That's a common myth, but experts believe the reason colds are more common in the winter is because we spend more time indoors around other people, who transmit their cold viruses to us by sneezing and leaving germs on surfaces that we touch.

If you're really bothered by your winter runny nose, try taking an over-the-counter decongestant. The prescription nasal sprays Ru-Tuss and Atrovent have also been found to be effective at drying up drippy noses.

Then there's always mom's advice: Before you go out in the cold, cover your nose and mouth with a scarf. Air breathed through fabric will be warmer and moister, which can cut down on those annoying drips.

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