Going outside with wet hair may give you a big headache. (Some people call this a brainfreeze headache.) But it won’t give you a cold. A cold is a virus. Cold viruses travel through the air in invisible droplets. When they get inside your body, your immune system kicks in to fight them. This leads to a stuffy nose, sore throat, and headache—in other words, a cold.
You have to come in contact with the cold virus to get a cold. And the cold virus has to come from someone who has a cold. The virus travels from a cold sufferer’s body to the rest of the world through sneezing, coughing, and touching.
And the virus can live for three hours as it travels around invisibly. So being around someone who has a cold can definitely cause a cold.
Bodies are also more likely to get a cold when they are run down. People who don’t get enough sleep or don’t eat healthfully are more likely to get colds.
And, if your body becomes extra chilled—say, from being outside with wet hair—it may get extra tired. That’s because it uses up energy shivering.
That extra tiredness can make it more likely that it will get sick. So, while being outside with wet hair won’t cause a cold, it may make it more likely that you’ll get sick if you come in contact with the cold virus.