Mothers who advise wrapping up on cold days are supported by medical researchers who have found people with cold toes are more likely to get runny noses.

In the experiment, 90 students were paid to sit with their bare feet in cold water for 20 minutes. Another 90 students kept their feet in an empty bowl.

Researchers at Cardiff University's Common Cold Centre found 13 of the students reported cold symptoms such as a runny nose or sore throat about five days later, compared to five cases in the control group.

Ron Eccles

"When you dip your feet into cold water, you cause a pronounced constriction of the blood vessels in the nose," said Prof. Ron Eccles of the centre. "This is one of the factors we believe that actually can aid the virus by lowering the defences within the nose."

Earlier studies that inoculated people with the cold virus and then chilled them did not find a link between temperature and showing cold symptoms.

Eccles's team thinks if less blood goes to the nose, fewer white blood cells are available to fight infection.

According to the researchers, many people are mildly infected during cold season but don't show any symptoms.

When people get chilled and the number of white blood cells in the nose drops, cold viruses have a chance to get stronger and a cold takes hold.

"It's an interesting observation," said Richard Tedder of University College London. "But at the end of the day, being coughed (at) in the face is going to give you a cold."

The Cardiff study, which is published in the journal Family Practice, also suggests there may be more colds in the winter because noses are colder during the season.