Cold water as good as hot to remove germs

Hot water is no more effective than cold at getting rid of bacteria, a new study suggests. Scientists discovered that washing hands in cool water removes just as many germs as hot water. Furthermore, antibacterial soap was no better than normal soap, the researchers found, suggesting savings could be made on energy.

HOT water is no more effective than cold at getting rid of bacteria, a new study on handwashing suggests.

Scientists have poured cold water on the theory that only a hot bath or shower gets you clean.

They discovered washing in cool water removes just as many germs as hot water.

Furthermore, antibacterial soap was no better than normal soap, the researchers found. The findings suggest savings could be made on energy bills, the researchers suggest.

Prof Donald Schaffner, a food scientist, said: “People need to feel comfortable when they are washing their hands but as far as effectiveness, this study shows us that the temperature of the water used didn’t matter.”

Just a short rub of the hands made a major difference the study, published in the Journal of Food Protection, found.

“Even washing for 10 seconds significantly removed bacteria from the hands,” said Prof Shaffer

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 at a time in water at 60, 79 or 100F (15.5, 26 and 38C) and using varying amounts of soap.

Neither the temperature nor the amount of soap used made any difference to the amount of bacteria removed simply by washing for just 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 allowed 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.”

NHS advice says hands should be run under tepid running water, before liquid soap is applied to every surface of them, and rubbed vigorously for at least 10-15 seconds.

The guidance from the National Institute of Health and Care Excellence says particular attention should be paid to the tips of the fingers, the thumbs and the areas between the fingers.

“Other areas to wash include the palms, back of the hands and the back of the fingers.”

The Health and Safety Executive recommends that hot water should be stored at 140F (60C) or higher in order to protect against legionnaire’s disease.