Hot is no better than cold for clean hands

‘Temperature of water does not matter’

Last year England’s deputy chief medical officer said no one spends long enough washing their hands. Dr Gina Radford said each wash should take around 45 seconds – as long as one verse of “God Save the Queen”. And that you should use hot water at 60C or higher. And you should get your hot water within a minute of a tap being turned on.

However, it turns out hot water is no better than cold at getting rid of germs, according to a US study on handwashing. Researchers discovered that washing in cool water removes just as many germs as hot water.

And antibacterial soap is no better than normal soap.

Food scientist Professor Donald Schaffner said: “People need to feel comfortable when they are washing their hands but as far as effectiveness, this study shows us the temperature of the water used doesn’t matter.

“This study may have significant implications towards water energy, since using cold water saves energy.” Just a short rub of the hands makes a major difference. “Even washing for 10 seconds significantly removed bacteria from the hands,” said Prof Schaffner.

Researchers from Rutgers university in New Jersey followed 21 volunteers over six months who had their hands exposed to harmless bacteria and who washed at various temperatures. They washed their hands for 10 seconds in water at 15.5C, 26C and 38C, using varying amounts of soap.

Neither water temperature or the amount of soap used made any difference to the amount of bacteria removed by washing for 10 seconds.

The researchers said it was more important to ensure people washed their hands at all, before preparing food and after using the lavatory, than it was to insist water was hot.

While the study suggested that the amount of soap made no difference to harmless bacteria, researchers said more work was needed to understand how much, and what type is needed to remove harmful microbes.

However, British experts were cautious about the findings – saying hotter water is needed in order for detergents to work properly.

Dr Lisa Ackerley, a food safety adviser for the British Hospitality Association, said: “Warm water is good as it helps the soap to lather and it’s the action of washing soap off which helps to get hands clean.

“But the actual water temperature won’t kill bacteria as it can’t be too hot or it would burn,” she said.