Although mothers have warned their children for generations that going out with a wet head will get them sick, this belief is actually largely unfounded and untrue.
The belief may be traceable back to French chemist Louis Pasteur. Back in 1878, he was doing numerous studies on animals and their susceptibility to the anthrax virus and noticed that chickens were immune. He performed an experiment in which he exposed chickens to anthrax and then chilled them in cold water. The chickens got sick and died. When he repeated the experiment and wrapped the chickens in warm blankets after being exposed, they also became sick but recovered.
Since then, studies conducted throughout the world have found that the combination of wet hair and cold temperatures has absolutely nothing to do with whether you will catch a cold. Still, mothers everywhere warn against it. Why? First let’s explore what causes the common cold in the first place.
The common cold is brought on by germs that carry the cold virus that pass from person to person, particularly when a person touches hands with an already infected person or breathes in particles of the air that’s just been sneezed out of someone with a cold. They do, in fact, occur more frequently in the cold winter months, but that doesn’t have to do with the temperature outside. This has to do with the fact that people are more often in close quarters during these months, making viruses spread more easily. This is why kids get sick more often in the winter too: It’s when school is in session and they’re busy swapping pencils, snacks and germs instead of playing outside. Also, cold weather tends to dry out the mucus lining of your nose, making it harder to fend off germs when they do get inside since they stick around (literally) more easily.
Bottom line: Can being outside with wet hair make you more susceptible to catching a cold when you’ve already been exposed to the one that your 4-year-old nephew has, the one that made him sneeze all over you? It’s a definite possibility. Does just being outside with wet hair in the cold cause you to catch a cold? Nope.
This brings up a whole other interesting topic, by the way: The relationship between our environment and illness. For example, the incidence of multiple sclerosis is higher the farther away from the equator you get. Coincidence? I think it's unlikely. Our environment definitely does play a role in illness.
Here's an article about more old wives’ tales you always thought were true, but aren’t.