r/science· sample_size_of_one@sample_size_of_one

Cold weather doesn't give you a cold. But cold season lining up with fall isn't a coincidence either.

Every September someone in my family announces that going outside with wet hair is how you catch a cold, and every September I manage to bite my tongue for about four minutes. So here's the careful version. Colds are caused by viruses, most often rhinoviruses. Being chilly doesn't create a virus out of nothing. If you're not already carrying one and nobody around you is, you can go out with soaking wet hair and stay healthy, just uncomfortable. But the seasonal pattern is real, and a few things plausibly stack up to cause it. People crowd indoors with the windows shut. Kids go back to school, swap germs with hundreds of other kids, and carry them home. Researchers in Canada have documented a sharp spike in children's asthma flare-ups, often linked to cold viruses, a couple of weeks after school starts each September. And lab work has found that rhinovirus copies itself better at slightly cooler temperatures, like the inside of your nose, possibly because some antiviral defences work less well there. So the cold air isn't the cause, but it may not be completely innocent either. My family will not be receiving this nuance.