The myth that cold weather can give you a cold is not, as it turns out, a myth. Researchers at Yale found that cold temperature causes the most common cold virus to replicate more easily and quickly in a mouse’s nasal cavity than at normal body temperatures, according to a recent study published in the journal Proceedings of the National Academy of Sciences.
The study hasn’t yet been conducted on humans, but the mechanics of the virus and the mouse’s immune system are similar, study co-auther Akiko Iwasaki tells Quartz. For a long time, doctors have held that colds flourish in the winter because lower temperatures drive people inside, where the limited ventilation and close contact increase contagion. Also, being outside in the cold can cause hypothermia, which weakens the immune system, and dryness in the nose that stops the body from filtering out the infection that causes a runny nose. And that, in turn, leads to a full-blown cold. But temperature itself hasn’t been pinpointed as a cause.
Those related causes still hold, Iwasaki says. The virus does need to already be in a person’s airway in order to multiply, and environmental factors do contribute to its spread. This study isolated all those factors; it looked at the normal airway cells of mice, and those airway cells without the typical immune responses that would protect both mice and humans. Without the immune system responses, the virus replicates in both cold (33 degrees Celsius) and normal (37 degrees Celsius) temperatures. But in the cells with the immune responses, the virus cells replicated quickly in the lower temperature, while the normal body temperature cells blocked the virus cells from replicating.
Iwasaki’s advice for the cold months? “Preventing the cold air from lowering the temperature in the nose is a good thing,” she says. That amounts to bundling up and covering your nose with a scarf, or the like.