Rates of upper respiratory infections peak in the winter, but can frigid temperatures actually trigger a cold? Although this claim has often been dismissed as unscientific folklore, one surprising study published in Family Practice suggests that there may actually be some truth to it.
A group of 180 brave, healthy volunteers were randomly assigned either plunge their bare feet in icy water for 20 minutes or to stay warm and dry during a control procedure. All participants were then asked to keep a diary of any cold symptoms, such as sneezing or a stuffy nose, they experienced before the procedure and during the next five days.
Nearly 29 percent of those who had endured the icy footbath developed colds, compared to less than 9 percent of the control group. The researchers report that chilling of the feet had previously been shown to cause blood vessel constriction in the upper airways, which may reduce the body’s defenses against respiratory infections, such as colds.
The scientists who conducted this experiment theorize that many people harbor dormant respiratory infections that become active when they are exposed to cold temperatures.
In other words, getting chilled caused some people who were already infected with rhinoviruses to come down with colds that their immune system might have fought off if they had stayed warm and dry.
“During prolonged exposure to cold, your body needs a lot of energy to stay warm, which can reduce your innate resistance to respiratory infections,” explains ear-nose-throat specialist Michael Benninger, MD, chair of the Head and Neck Institute of the Cleveland Clinic.
However, this study isn’t designed to show cause and effect: the research only shows an association between getting chilled and getting sick.
“While there’s some evidence that cold weather has an impact for getting a cold, what’s much more important is how we change our behavior during winter months,” says Dr. Benninger.
“When it’s cold outside, we tend to stay indoors, often in crowded environments, and are therefore exposed to many more people with colds, which is why there’s a dramatic increase in upper respiratory infections during the winter,” he adds.
Colds, which are highly contagious, are often spread by hand-to-hand contact with an infected person or less commonly by inhaling virus-laden droplets released when the person coughs or sneezes.
The rhinoviruses that cause sniffles can survive for several hours on contaminated surfaces—an ATM screen, elevator button, or door knob—someone with a cold has handled, according to Dr. Benninger.
Washing your hands frequently with soap and water is the best way to ward off sniffles and other contagious illnesses. As I reported recently, 40 million Americans fall prey each year to diseases spread by hands, which can harbor up to 500,000 bacteria per square centimeter.
When 40,000 Navy recruits were taught to wash their hands five times a day, their rate of respiratory infection dropped by 45 percent, a study published in American Journal of Preventive Medicine reported.
“There are also very good studies in college students showing that those who did regular aerobic exercise had one-third fewer colds than those who didn’t,” reports Dr. Benninger. “The theory is that by increasing your heart rate, T-cells and B-cells on your capillary walls get propelled into the bloodstream and boost immunity.”
And the more you work out, the safer you are likely to be from colds. A 2010 study of 1,002 adults ages 18 to 85 reported that those who exercised the most had 46 percent fewer days of illness due to upper respiratory tract infections, compared to those who exercised the least.
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