180 volunteers were recruited for the study during the common cold season in Cardiff (October to March). The volunteers took their shoes and socks off and half had their feet chilled in ice cold water for 20 minutes while the others sat with their feet in an empty bowl. 29% of the chilled volunteers developed cold symptoms over the next 4-5 days compared to only 9% in the control group.
Professor Ron Eccles said: "When colds are circulating in the community many people are mildly infected but show no symptoms. If they become chilled this causes a pronounced constriction of the blood vessels in the nose and shuts off the warm blood that supplies the white cells that fight infection. The reduced defences in the nose allow the virus to get stronger and common cold symptoms develop. Although the chilled subject believes they have "caught a cold" what has in fact happened is that the dormant infection has taken hold."
Common colds are more prevalent in winter than summer and this may be related to an increased incidence of chilling causing more clinical colds, but another explanation put forward in a review article published by the Centre is that our noses are colder in winter.
"A cold nose may be one of the major factors that causes common colds to be seasonal. When the cold weather comes we wrap ourselves up in winter coats to keep warm but our nose is directly exposed to the cold air. Cooling of the nose slows down clearance of viruses from the nose and slows down the white cells that fight infection. Mothers can now be confident in their advice to children to wrap up well in winter."