No, Going Out In The Cold Doesn’t Make You Sick

You’ll catch your death out there—except not.
Let’s start with the straight dope: Cold weather doesn’t make you sick. Viruses and bacteria make you sick.
That said, frosty winter conditions make it easier for those germs to spread.


SELF reached out to two experts—Charles Gerba, Ph.D., professor of microbiology and environmental sciences at the University of Arizona, and Beth Ricanati, M.D., a California physician specializing in women's health and wellness—to get the scoop.

When temperatures drop, so, too, do humidity levels, and drier air makes it easier for pathogens—the flu virus in particular—to get passed around, Gerba says.

Influenza floats through the air on tiny droplets. When it’s humid out, these droplets pick up water from the air, which makes them heavier, causing them to fall to the ground before they get very far. In the winter, however, when there is little moisture in the air, the viruses stay up longer, traveling farther and therefore passing more effectively from person to person.

This also helps them live on surfaces longer.

The rhinovirus that causes colds doesn't seem to spread farther in dry air. But that doesn't really matter when you're nose-to-nose-to-nose with a hundred strangers on a packed commuter train on a snowy day.

Fun fact: A sneeze can send viruses flying six feet or more, Gerba says.

Another thing: Cold can mess with your body's natural defense systems.

For one thing, the frigid, dry air outside—along with the artificially dry air indoors that comes from blasting the heat—dries out your snot.


Nasal mucus filters out germs from the air you breathe and traps them so you can get rid of them by blowing your nose. Breathing dry air can dry out the mucosal layer, making it less able to do its important, albeit sticky, job.

At the same time, the cold makes the blood vessels in the mucosa constrict, decreasing available moisture from the inside, too, says Ricanati.

Then, she explains, when you come inside where it’s warm, these vessels dilate, which can cause congestion. And congestion leads to mouth breathing. And that circumvents the entire nasal mucosa germ-filtering system designed to keep viruses out.

There is also some evidence that lower temperatures suppress an immune function of cells, dampening their ability to fight off cold viruses. So you might actually be worse at fending off illness in the winter.

The takeaway here is that cold doesn't make you sick, but it can make you more likely to get sick.

But there's plenty you can do to protect yourself. Get a flu shot every year. Wash your hands. A lot. (With soap!) And in between washings, try not to touch your face too much, because that's an easy way for germs to get in.