As the season of sneezing and grabbing tissues begins with the autumn’s first frosts, medical researchers have found that “granny’s nostrums” to fend off colds may be scientifically proven.

Ninety volunteers who spent 20 minutes with their feet in bowls of iced water have provided evidence that failing to wrap up warmly is directly linked to falling prey to sore throats and a bunged-up nose.

Although apparently common sense, straightforward connections between chilling and viral infection have been hard to prove, according to the common cold centre at Cardiff University – the world’s only centre dedicated to researching and testing new medicines for the treatment of flu and the common cold.

But the latest experiment reinforces theories that existing, latent infection can be activated when parts of the body, particularly the feet and nose, get wet and cold.

Claire Johnson and Ron Eccles from the centre found that 29% of the volunteers developed cold symptoms within five days, compared to 9% of a control group who dangled their feet in empty bowls.

All participants took off their shoes and socks and temperatures were monitored throughout the experiment.

“When colds are circulating, many people are mildly infected but show no symptoms,” said Professor Eccles, whose findings are published in today’s issue of Family Practice magazine.

“But 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.

“Although the chilled subject believes they have ‘caught a cold’, what has in fact happened is that the dormant infection has taken hold.”

Parents should feel confident in telling children to wrap up warmly this winter, the researchers say – though a nose-protecting garment, possibly like the one worn by Harry Potter, would be a useful fashion accessory.

Gesundheit!