Research has previously shown that a person cannot get a common cold from exposure to cold temperatures. Only a virus can cause a cold. But stress can wear down the body's immune system and make you more susceptible.
However, new research in Wales during 2005 showed that drops in body temperature can cause a cold to develop. The researches theorize that, when the body is chilled, there is a pronounced constriction of the blood vessels in the nose which shuts off the warm blood that supplies the white cells that fight infection, allowing a virus in the nose to get stronger. While people really haven't "caught a cold," what in fact happens is that a dormant infection has taken hold.
To keep from catching a cold you must avoid contact with the virus. To do this, keep your hands clean and stay away (at least 3 feet) from sick people.
Research studies on volunteers show that 95 percent will succumb to infection if a dose of virus-rich nose drops introduces the virus into the body. This suggests that exposure to the virus (frequency and/or intensity) is one of the most important factors in determining whether or not you will catch a cold.
Despite being infected, one in four won't experience typical symptoms. Although they are infected, they don't know that they have a cold.
It's unknown why 100 percent of those exposed to the virus do not succumb, and why 25 percent of those infected don't know it. It probably has something to do with the power of the immune system in general and/or how well the immune system happens to be working at the time of the exposure.
Another often heard reason that colds are more likely to occur in cold weather is that heat from a furnace dries the mucous membranes in the nasal passages, compromising their ability to dampen the impact of an invading virus. However, research says this is not true, and that the mucous membranes appear to be able to function quite well, even when they feel dried out.
It's likely the main culprit is that in cold weather we congregate indoors. There is more constant contact with others, and if someone has a cold, his sneezing and coughing thrusts the virus into the enclosed environment, increasing exposure and the risk of infection in those nearby.