Here’s a pretty good reason to stay warm: to (potentially) prevent catching a cold.(Photo: Getty Images)

Your grandma probably told you to bundle up for the winter weather as a kid or you’d risk getting sick. While that notion has been hotly debated for ages, a new study out of Yale University provides some evidence that Grandma was right.

The common cold virus can reproduce more efficiently in the cooler temperatures found inside your nose than at your core body temperature — say in your lungs or the rest of your body. While that may surprise you, flu researchers have known this tidbit for more than 50 years — and that’s probably one of the places where your grandma’s advice came from.

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It’s your immune system’s job to fight back against rhinovirus (the virus that causes the common cold), so hypothetically it doesn’t matter how much of the gunk is replicating in your nose, as long as your body fights it. And it’s that exact point that the Yale researchers wanted to isolate: What if body temperature actually impacts our immune system’s ability to fight back against the nasty virus?

In other words, if you let yourself get chilled, is your body less able to fight off a cold?

To answer this question, researchers took cells from the airways of mice and examined them closely for immune response to rhinovirus. Some of the cells were incubated at 37 degrees Celsius (AKA 98.6 degrees Fahrenheit, or the average core human body temperature), while other were incubated at a significantly cooler 33 degrees Celsius.

The team found that the cells’ natural immune response to the cold virus was impaired at the lower temperature. The study, which was published in the journal Proceedings of the National Academy of Sciences, indicated that the temperature drop reduced the immune system’s ability to eradicate the virus; the cooler temperature did not simply promote the virus’s ability to breed.

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This study suggests that immune systems seem to work better in those normal, warmer body conditions, according to article co-author Akiko Iwasaki, Ph.D, a professor of immunobiology and molecular biology at Yale.

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“At the core body temperature, the rhinovirus is detected by the host immune system better, and the factors that block virus replication, type I interferons, work better at the higher temperature,” she tells Yahoo Health.

Mice were used for this study, so the theory doesn’t automatically translate to humans, too. Iwasaki says more studies will have to be done. “But if similar mechanisms operate in humans, I would think that being exposed to the cold air would reduce nasal-cavity temperature, and makes one more susceptible to virus replication.”

So you can tell Grandma that she might have been onto something. “This study would support the idea that the cold weather is a risk factor, by reducing the immune response to the cold virus,” Iwasaki explains. “It would not hurt to bundle up in cold weather,” especially around the nose and air passageways, she says, where the virus is prone to replicating — and infecting you with a bug.

So grab your warm hat — or better yet, a balaclava. If nothing else, this study is one good reason you should stay warm to (potentially) prevent cold.

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