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
Why Does Asparagus Make Your Pee Smell Funny?

The asparagus has a long and storied history. It was mentioned in the myths and the scholarly writings of ancient Greece, and its cultivation was the subject of a detailed lesson in Cato the Elder's treatise, On Agriculture. But it wasn't until the turn of the 18th century that discussion of the link between asparagus and odorous urine emerged. In 1731, John Arbuthnot, physician to Queen Anne, noted in a book about food that asparagus "affects the urine with a foetid smell ... and therefore have been suspected by some physicians as not friendly to the kidneys." Benjamin Franklin also noticed that eating asparagus "shall give our urine a disagreeable odor."

Since then, there has been debate over what is responsible for the stinky pee phenomenon. Polish chemist and doctor Marceli Nencki identified a compound called methanethiol as the cause in 1891, after a study that involved four men eating about three and a half pounds of asparagus apiece. In 1975, Robert H. White, a chemist at the University of California at San Diego, used gas chromatography to pin down several compounds known as S-methyl thioesters as the culprits. Other researchers have blamed various "sulfur-containing compounds" and, simply, "metabolites."

More recently, a study demonstrated that asparagusic acid taken orally by subjects known to produce stinky asparagus pee produced odorous urine, which contained the same volatile compounds found in their asparagus-induced odorous urine. Other subjects, who normally didn't experience asparagus-induced odorous urine, likewise were spared stinky pee after taking asparagusic acid.

The researchers concluded that asparagusic acid and its derivatives are the precursors of urinary odor (compared, in different scientific papers, to the smell of "rotten cabbage," "boiling cabbage" and "vegetable soup"). The various compounds that contribute to the distinct smell—and were sometimes blamed as the sole cause in the past—are metabolized from asparagusic acid.

Exactly how these compounds are produced as we digest asparagus remains unclear, so let's turn to an equally compelling, but more answerable question:


Remember when I said that some people don't produce stinky asparagus pee? Several studies have shown that only some of us experience stinky pee (ranging from 20 to 40 percent of the subjects taking part in the study, depending on which paper you read), while the majority have never had the pleasure.

For a while, the world was divided into those whose pee stank after eating asparagus and those whose didn't. Then in 1980, a study complicated matters: Subjects whose pee stank sniffed the urine of subjects whose pee didn't. Guess what? The pee stank. It turns out we're not only divided by the ability to produce odorous asparagus pee, but the ability to smell it.

An anosmia—an inability to perceive a smell—keeps certain people from smelling the compounds that make up even the most offensive asparagus pee, and like the stinky pee non-producers, they're in the majority.

Producing and perceiving asparagus pee don't go hand-in-hand, either. The 1980 study found that some people who don't produce stinky pee could detect the rotten cabbage smell in another person's urine. On the flip side, some stink producers aren't able to pick up the scent in their own urine or the urine of others.

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

Frazer Harrison/Getty Images
Big Questions
What Legal Authority Does Judge Judy Have?
Frazer Harrison/Getty Images
Frazer Harrison/Getty Images

While Judith Sheindlin was a real, live judge—New York City Mayor Ed Koch appointed her to family court in 1982 and then made her Manhattan's supervising family court judge in 1986—she's not acting as one on her show. Neither are any of the other daytime TV judges (whether they passed the bar and served as actual judges or not).

TV court shows don't take place in real courtrooms and they don't feature real trials, though they are usually real cases—the producers often contact parties who have pending litigation in small claims court and offer them the opportunity to appear on TV instead. What you're seeing on these TV court shows is really just arbitration playing dress-up in small claims court's clothes.

Arbitration is a legal method for resolving disputes outside the court. The disputing parties present their cases to a neutral, third-party arbitrator or arbitrators who hear the case, examine the evidence, and make a (usually binding) decision. Like a court-based case, arbitration is adversarial, but generally less formal in its rules and procedures.

The power that Judge Judy and the rest of the TV arbitrators have over the disputing parties is granted by a contract, specific to their case, that they sign before appearing on the show. These contracts make the arbitrators' decision final and binding, prevent the disputing parties from negotiating the terms of the arbitration, and allow the "judges" wide discretion on procedural and evidentiary rules during the arbitration.

TV judges make their decision on the case and either decide for the plaintiff, in which case the show's producers award them a judgment fee, or with the defendant, in which case the producers award both parties with an appearance fee. This system seems to skew things in favor of the defendants and gives them an incentive to take their case from court to TV. If they have a weak case, appearing on the show absolves them of any financial liability; if they have a strong case, they stand to earn an appearance fee along with their victory.

If one party or the other doesn't like the arbitrator's decision, it can really only be successfully appealed if it addresses a matter outside the scope of the contract. In 2000, Judge Judy had one of her decisions overturned for that reason by the Family Court of Kings County. In the case B.M. v. D.L., the parties appeared in front of Sheindlin to solve a personal property dispute. Sheindlin ruled on that dispute, but also made a decision on the parties' child custody and visitation rights. One of the parties appealed in court, and the family court overturned the custody and visitation part of the decision because they weren't covered by the agreement to arbitrate.

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

This post originally appeared in 2012.


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