Does cold weather really make you catch a cold?
People say that if you go outside in cold weather without a jacket, you will “catch a cold.” Assuming that is true, how come? I always thought you “catch a cold” by coming into contact with a virus, writes Michael Green, of Seaford, NY.
Mothers and grandmothers have traditionally raised the cold-weather alarm: Bundle up, change wet socks and shoes, don’t sit in a draft and get chilled. The idea that sneezing, sniffling, stuffy noses, fever, and body aches are caused by getting chilled is a very old one. People have talked about catching “colds” since at least the 1500s. The common sickness was called a “cold” because its cause, people thought, was miserably cold weather.
We now know that colds (and flu) are the result of infection–an overwhelming of the body’s defenses by tiny, invading viruses. The first viruses were discovered in the late 1800s. By the 1930s, scientists suspected that viruses were to blame for colds; proof came in the 1940s. Since then, we’ve learned that colds can be caused by some 200 different viruses, often from the rhinovirus group.
But the billion or so colds we catch in the U.S. each year do tend to cluster in the colder months of fall and winter. Why? One reason is that we spend more time indoors in winter, in close contact with other people. The low humidity of winter weather may also help cold viruses flourish, especially in our dried-out noses.
And scientists studying the flu, a much more serious respiratory infection, have found evidence that cold, dry weather plays an important part in the yearly winter outbreaks. Researchers exposed guinea pigs to a flu virus under different combinations of temperature and humidity. No healthy animals were infected when the humidity was held at a steamy 80 percent, or when the temperature hovered at a summery 86 F. But flu transmission soared when humidity dropped to below 35 percent, and when the temperature was lowered to about 41 F.
According to researchers, winter’s cold dryness helps the flu virus survive in air longer, and get a foothold in the nose, where protective mucus dries out. (There is little flu in the tropics, where the weather is warm and humid all year long.)
Another study in the U.K. connects cold with colds. Volunteers who plunged their feet into chilly, 50-degree F. water for 20 minutes were more likely to develop cold symptoms over the following week than those whose feet stayed warm. Researchers say that when the body harbors a cold virus, held in check by the immune system, chilled, wet feet may predispose us to a full-blown illness.
Some scientists think that there’s another piece of the summer/winter puzzle: Vitamin D. In summer, when UV radiation from the Sun peaks, our Vitamin D levels rise. As days grow shorter, Vitamin D levels fall, reaching their lowest levels in late winter, the peak of cold and flu season. Since Vitamin D plays an important role in the immune system, making sure our levels are adequate in winter may help us fight off the viruses that cause colds and flu.
