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Does being cold really make you sick, or is that just an old wives tale? – M.H. Woolwich, ME.

Thanks for the question, M.H. You hear this one all the time – is it true?

The short answer is no. “Sick” in this context is generally assumed to mean the flu or the common cold. The cause of these diseases are viruses – influenza virus and rhinovirus, respectively. You cannot catch a cold or the flu without being exposed to these viruses, no matter now cold you get – even if you go out without a jacket, or don’t wear a hat, or forget your mittens. Now, if you get really really cold, and your core body temperature drops below 95°F (normal is 98.6°F), that’s called hypothermia, which can be very dangerous. If you classify hypothermia as “sick”, then I guess the old saying is true, but not if you are just talking about catching a cold or the flu.

There is a long answer too, and it’s… kinda. While being cold doesn’t make you sick, two side effects of cold weather make it easier for viruses to infect you. The first is the low humidity associated with low temperatures (and indoor heating systems), which dry out the mucus membranes of your nose, making it more susceptible to infection. The second is that cold weather tends to make people spend more time indoors in close contact with other people, where they are more likely to spread viruses.

A few years ago, a group of researches at Yale University also demonstrated that cells and mice at lower temperatures have a more difficult time fighting off viruses. It’s not entirely clear if this same effect occurs in humans, and if so, how much it might increase the odds of someone catching a cold or the flu, but it’s pretty cool.

Also, the author’s assumption is that cold air in your lungs and airways was the culprit here. When you think about this, it means that going out in the cold might increase your chances of catching a cold or the flu regardless of how cold a person might actually feel. In other words, even if you are bundled up in a coat, hat, scarf, and mittens, you are still breathing the same cold air when you go outside, so your risk of getting sick would be unaffected by how you dress or how cold you actually felt. The same is true for the effects of low humidity in cold weather.

So in the end, even if cold weather might fundamentally increase your risk of getting sick, being cold (or not dressing warmly enough) will not. The best thing you can do is wash your hands, avoid friends and family who are sick, and of course, get the flu vaccine.