CARDIFF, Wales, Nov. 14 - Mom was right, say British researchers. Getting a chill can bring on a cold. So bundle up and keep your feet warm and dry.
Infectious disease specialists may ridicule the hoary concept that cold wet feet can trigger the symptoms of a common cold. Viruses cause these infections, not wet feet, they argue. But a team headed by Ronald Eccles, Ph.D., D.Sc., of Cardiff University here is recommending a new look.
Action Points
- Explain to patients who ask that this study indicates an association between chilling and the development of cold symptoms in subjects with a history of frequent colds. It does not address the issue of whether or not there is an association between chilling and infection with a virus.
Dr. Eccles said the results of a randomized study bear out a two-pronged hypothesis: that many of us carry around a subclinical cold infection and that chilling the feet opens the door for it to become a full-blown cold.
A hundred years ago, doctors would have said that a chill clearly leads to infection, he said. People then would have been both more exposed to the elements when they were outside and less likely to have a nice, centrally heated home in which to take shelter, he said. "We're better protected now," Dr. Eccles said, so we may not see the chill-cold connection as clearly.
But when he and a colleague deliberately chilled subjects -- by dipping their feet in ice water -- they found that those who got their feet cold and wet were significantly more likely to develop symptoms of a cold over the next four or five days than were those who just put their feet in an empty bowl.
The researchers randomized 180 healthy participants to 20 minutes of water at 10 degrees C or an empty bowl. In the current issue of the journal Family Practice, they reported:
- There was no difference in acute cold symptoms immediately after the experiment.
- After a few days, 13 of the 90 participants who were chilled reported they were suffering from the symptoms of a cold, compared with five of the 90 controls. The result was statistically significant at p = 0.047.
- The 18 participants who came down with symptoms of a cold also reported that they were more likely to suffer colds during the year than did the 162 who remained healthy. The result was statistically significant at p = 0.007.
"When colds are circulating in the community, for every person you see who is symptomatic, there are two or three who have a sub-clinical infection," Dr. Eccles said. "It's those people who are prone to developing a common cold when they are chilled -- they've already got the virus, but the chilling is actually reducing their respiratory defense."
It's well known, he said, that chilling the feet causes vasoconstriction in the nose. That has two common cold-producing effects, he says. It reduces number of immune cells available in the nasal epithelium and slows down mucociliary clearance, allowing infectious agents more time to do their dirty work.
The finding may vindicate moms everywhere, but it flies in the face of research dating back nearly 40 years that appeared to rule out the chill/cold connection.
In those studies, researchers chilled subjects and then challenged some of them with a cold-causing virus. The result: controls and chill victims came down with colds at about the same rate.
But, says Dr. Eccles, those studies had two main flaws -- they were small and they didn't reflect the real-world situation, where a horde of viruses circulates, sometimes causing disease and sometimes not.
Dr. Eccles pointed out that this study does not address infection with a virus but only the development of symptoms after exposure. "The results of the present study demonstrate that chilling is associated with the onset of common cold symptoms but the study does not provide any objective evidence, such as virology, that the subjects were infected with a common cold virus."
The next step for his research, he said, would be to couple the chilling study with tests to see which viruses are actually causing the illness in those who come down with a cold.
That may not be easy: "When you're dealing with (wild-type) colds, you never know which virus you're dealing with and it's fairly difficult to isolate and identify the viruses," he said. But technology is improving, he added, so that work may soon be possible.
He'd also like to see what happens in more extreme situations: "Dipping your feet in cold water for 20 minutes is not really a severe chilling," Dr. Eccles said.