New research seems to support what you probably heard your whole childhood: Bundle up, stay warm or you’ll catch your death of cold!
As it turns out, your immune system turns sluggish in the cold, and the cold virus grows better in the slightly chillier environment of your nose than at the body's normal core temperature. That's the conclusion of a mouse study published this week in the Proceedings of the National Academy of Sciences.
“The optimal temperature for the cold virus to replicate is around 33 degrees Celsius (91.4 degrees Fahrenheit), which is found in the nose of most people living in normal conditions,” says Akiko Iwasaki, a professor of immunology at Yale University and one of the authors on the paper.
As temperatures drop outside, humans breathe in colder air that chills their upper airways just enough to allow cold viruses to flourish, says Ellen Foxman, Iwasaki's colleague. The recent study suggests that if you can keep your nose warmer, the virus won’t replicate as easily.
Does that justify what your mother — and probably your grandmother, too — said for all these years? “I think we provided at least one scientific mechanism for why that might be true,” Iwasaki says with a laugh.
Two things are happening when the temperature drops inside the nose: First, every cell in the body has sensors that detect viruses inside it and these sensors don't work as well when the temperature drops to 33 degrees Celsius. Second, these sensors trigger another set of molecules known as interferons, which bind to the neighboring cells to alert them to make antiviral proteins. At the lower temperature, interferons don't induce the production of antiviral proteins as effectively.
These two reactions help the virus grow better, which makes it more likely that enough of it will grow in your nose to make you sick and spread it to other people. This may help explain why people get more colds in the winter than in the summer. The textbook explanation in medical school is that colds are more common in winter because people are more crowded into enclosed indoor spaces. Iwasaki thinks the colder temperature may also play a role.
“It makes a lot of sense if you look at the seasonality of the common cold. Usually you get it when the temperature is colder,” she notes. “So, we might have added one more explanation to why people catch colds.”
Covering your nose to keep it warmer may actually help. “I started doing that once we found these results,” Iwasaki says. “I wear a scarf around my face. It doesn't look that great, but I haven't caught a cold yet — so maybe it's working.”
And by the way, if you try boosting your immune system by using supplements or eating chicken soup, you may be fooling yourself.
“Because we have these two main defects [in the immune system] at the lower temperature, anything that relies on the immune system to block the virus is not going to work very well at [that] temperature,” Iwasaki says. “Just increasing the temperature [inside your nose] is the best remedy against the cold.”
So wear that scarf around your nose. What’s more important, after all — staying healthy or looking attractive? (Don’t answer that…)