Hot water is no better than cold for killing germs by hand washing, says study


Hot water is no more effective than cold at getting rid of bacteria, a new study on hand washing suggests. Scientists discovered washing in cool water removes just as many germs as hot water.

Not only that, antibacterial soap was no better than normal soap the researchers found.

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 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.

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 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.”

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