Does Being Cold Make You More Susceptible to Getting a Cold?

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“Put a jacket on if you’re going out there, or you’ll catch a cold.”

It’s a common refrain of grandmothers all over the world. Are they right, though? Do low temperatures have anything to do with catching the common cold? Most of the scientific evidence is strongly against her, but Granny just might be on to something.

Sure, people tend to get sick during the late fall and winter. An estimated 5 to 20 percent of Americans come down with colds or flu every year around that time, and the temperature’s supposed influence is easily seen in both the names cold and influenza (traced to the Italian influenza di freddo, or “influence of the cold”). The folk wisdom naturally goes that the two must be connected.

But, as any doctor will tell you, colds and the flu are caused by viruses that happen to surge seasonally. Scientists used to think that viruses from the temperate regions went into a dormant state during the summer months, but now they think that the viruses are actually quite busy during the “off season” and are transmitted throughout populations all over the world. A 2007 study by researchers at Pennsylvania State University found that the influenza A virus, for example, exchanges genetic information with viral strains from below the equator – theoretically in a geographic area that would act as an influenza melting pot and viral reservoir – during its globetrotting, and is reintroduced to its home turf with enough genetic differences to fool our immune systems. It’s kind of like the swallows’ annual return to San Juan Capistrano, only the swallows come back to give everyone runny noses and coughs.

Scientists still struggle, though, with what exactly triggers people getting infected with the reintroduced viruses in fall and winter. Researchers have proposed several explanations, which might work alone, simultaneously but separately, or in combination with each other. They include:

Weather and climate - The flu and colds appear to do very well in cold winter temperatures and the dry air that goes with them. They can survive longer in dry air than moist air and hold out longer on exposed surfaces (counters, doorknobs, keyboards, etc.) when they’re cold. Dry air means dehydrated mucus and drier nostrils and airways, which could make it easier for the viruses to make themselves at home once they're passed to us. A study on guinea pigs showed that the transmission of influenza is enhanced in dry (20 percent humidity), cold (41 degrees) air and declines as the temperature and humidity rise (at 86 degrees or 80 percent humidity, it wasn’t transmitted at all).

Human behavior - With school in session and people generally spending more time indoors and in close contact with each other, the viruses have an easy time being transmitted among sizable groups of hosts. Even in tropical and equatorial regions that don’t have a winter and where flu occurs throughout the year, there are spikes during the rainy season when people spend time together indoors.

Human physiology - Humans and many other mammals experience seasonal physiological changes, often tied to the light/dark cycle. In the winter, any number of tweaks to our immunity - such as a decrease in vitamin D production - could make us more susceptible to the virus for a few months out of the year.

Paging Dr. Grandma

Babcias, bubbies and nanas, it turns out, also have at least a little evidence on their side.  A few years ago, Ron Eccles, director of the Common Cold Centre in Cardiff, UK, tested the idea that getting cold or damp might activate the viruses, and found that there might be a grain of truth to folk wisdom, and that being cold could indirectly contribute to getting sick.

Eccles chilled the feet of half of his subjects in the lab, and let the other half keep their feet warm in socks and shoes. After returning to their lives, people tracked their cold symptoms in journals. After four or five days, the subjects who got cold feet in Eccles’ experiment had more than twice as many sick people among their ranks (14.4% of the group) as the control group (5.6%).

One possible explanation for Eccles' results is that cold causes vasoconstriction, or a tightening of the blood vessels. This happens especially to the vessels close to the outside world, like in your nose, throat and mouth. This slows the flow of infection-fighting white blood cells to these areas, and also leads to dryness and hinders the nose's ability to filter the air.

(An important caveat to keep in mind with Eccles’ study is that people who had been cold in the lab only reported that they had cold symptoms afterwards. No medical tests were done to confirm that they had an infection.)

All this being said, we think you should feel free to go outside without your mittens on or with wet hair, unless Grandma is actually around. The bulk of the medical research isn’t on her side, but a stern look from Nana can trump all the empirical evidence in the world.

Today we're answering 20 big questions like this one. We'll plan more days like this, so if you have something you're dying to know, leave us a comment or tweet @mental_floss with the hashtag #bigquestions.

Big Questions
Where Should You Place the Apostrophe in President's Day?

Happy Presidents’ Day! Or is it President’s Day? Or Presidents Day? What you call the national holiday depends on where you are, who you’re honoring, and how you think we’re celebrating.

Saying "President’s Day" infers that the day belongs to a singular president, such as George Washington or Abraham Lincoln, whose birthdays are the basis for the holiday. On the other hand, referring to it as "Presidents’ Day" means that the day belongs to all of the presidents—that it’s their day collectively. Finally, calling the day "Presidents Day"—plural with no apostrophe—would indicate that we’re honoring all POTUSes past and present (yes, even Andrew Johnson), but that no one president actually owns the day.

You would think that in the nearly 140 years since "Washington’s Birthday" was declared a holiday in 1879, someone would have officially declared a way to spell the day. But in fact, even the White House itself hasn’t chosen a single variation for its style guide. They spelled it “President’s Day” here and “Presidents’ Day” here.

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Maybe that indecision comes from the fact that Presidents Day isn’t even a federal holiday. The federal holiday is technically still called “Washington’s Birthday,” and states can choose to call it whatever they want. Some states, like Iowa, don’t officially acknowledge the day at all. And the location of the punctuation mark is a moot point when individual states choose to call it something else entirely, like “George Washington’s Birthday and Daisy Gatson Bates Day” in Arkansas, or “Birthdays of George Washington/Thomas Jefferson” in Alabama. (Alabama loves to split birthday celebrations, by the way; the third Monday in January celebrates both Martin Luther King, Jr., and Robert E. Lee.)

You can look to official grammar sources to declare the right way, but even they don’t agree. The AP Stylebook prefers “Presidents Day,” while Chicago Style uses “Presidents’ Day.”

The bottom line: There’s no rhyme or reason to any of it. Go with what feels right. And even then, if you’re in one of those states that has chosen to spell it “President’s Day”—Washington, for example—and you use one of the grammar book stylings instead, you’re still technically wrong.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at

Quinn Rooney, Getty Images
Big Questions
How Do You Steer a Bobsled?
 Quinn Rooney, Getty Images
Quinn Rooney, Getty Images

Now that the Olympics are well underway, you might have developed a few questions about the games' equipment. For example: How does one steer a bobsled? Let's take a crack at answering this pressing query.

How do you steer a bobsled?

Bobsled teams careen down an icy, curving track at up to 90 miles per hour, so steering is no small concern. Drivers steer their sleds just like you steered your childhood sleds—by manipulating a pair of ropes connected to the sled's steel runners. The driver also gets help from the rest of the crew members, who shift their weight to aid with the steering.

Why do speed skaters wear glasses?


Speed skaters can fly around the ice at upwards of 40 mph, so those sunglasses-type specs they wear aren't merely ornamental. At such high speeds, it's not very pleasant to have wind blowing in your eyes; it's particularly nightmarish if the breeze is drying out your contact lenses. On top of that, there's all sorts of ice and debris flying around on a speed skating track that could send you on a fast trip to the ophthalmologist.

Some skaters also say the glasses help them see the track. American skater Ryan Bedford recently told the Saginaw News that his tinted shades help him focus on the track and filter out distracting lights and camera flashes from the crowd.

What kind of heat are the biathletes packing?

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As you might guess, there are fairly strict rules governing what sort of rifles biathletes carry on the course. They are equipped with guns chambered for .22 LR ammunition. The gun must weigh at least 3.5 kilograms without its magazines and ammunition, and the rifle has to have a bolt action or a straight-pull bolt rather than firing automatically or semi-automatically.

Is a curling stone really made of stone?

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You bet it is, and it's not just any old stone, either. Curling enthusiasts swear by a very specific type of granite called ailsite that is only found on the Scottish island of Ailsa Craig. Ailsite supposedly absorbs less water than other types of stone, so they last longer than their competitors.

Ailsa Craig is now a wildlife sanctuary, so no new ailsite has been quarried since 2002. As a result, curling stones are incredibly expensive. Kays of Scotland, which has made the stones for every Olympics in which curling has been an official event, gets prices upwards of $1,500 per stone.

What about the brooms?

The earliest curling brooms were actual brooms made of wood with straw heads. Modern brooms, though, are a bit more technologically advanced. The handles are usually made of carbon fiber, and the heads can be made of synthetic materials or natural hair from horses or hogs. Synthetic materials tend to be more common now because they pull all of the debris off of the ice and don't drop the occasional stray bristle like a natural hair broom might.

What are the ski jumpers wearing?

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It may look like a ski jumper can pull on any old form-fitting bodysuit and hit the mountain, but things are a bit more complicated than that. Their suits have to be made of a spongy material and can't be thicker than five millimeters. Additionally, the suits must allow a certain amount of air to pass through them; jumpers wearing suits without sufficient air permeability are disqualified. (This rule keeps jumpers from wearing suits that could unfairly act as airfoils.) These rules are seriously enforced, too; Norwegian skier Sigurd Petterson found himself DQed at the 2006 Torino Games due to improper air permeability.

Those aren't the only concerns, though. In 2010, judges disqualified Italian jumper Roberto Dellasega because his suit was too baggy.

What's up with the short track speed skaters' gloves?

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If you watch a bit of short track speed skating, the need for gloves quickly becomes apparent. When the skaters go to make passes or careen around a turn, they need the gloves to keep from cutting their hands due to incidental contact with other skaters' blades.

There's more to the gloves than just safety, though. Since the skaters' hands often touch the ice during turns, they need hard fingertip coverings that won't add friction and slow them down. The tips can be made of any material as long as it's hard and smooth, but you've got to give American skater Apolo Ohno some style points for the gold-tipped left glove he broke out in 2010.


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