American scientists have examined the theory that washing hands with hot water kills more microbes than water at ambient temperature and where they ended up.
The small study was conducted on 20 people who used water at 15 ° C to wash their hands and water at 38 ° C. The result, with regard to the removal of microbes, was the same: the hands were as clean, regardless of whether hot or cold water was used to wash the volunteers.
The study, published in the journal Journal of Food Protection, notes that its effects could help to reduce electricity consumption (and electricity bills) in restaurants and homes. In general, however, the hand washing guidelines of most countries do not constitute a specific water temperature.
However, scientists from Rutgers-New Brunswick University wanted to consider whether popular wisdom about the benefits of lukewarm or hot water and official hot water guidelines in the food and food industry in the US had some basis.
So they asked 20 people to wash their hands 20 times each with water at 15 ° C, 26 ° C or 38 ° C. Volunteers were also asked to test a variety of soaps. Before the trials started, the volunteers' hands were covered with harmless microbes. The researchers concluded that there was no difference in the number of microbes removed, regardless of the change in water temperature or the amount of soap.
"People need to feel comfortable when they wash their hands with hot water. As the research has shown, in terms of efficiency, the temperature of the water used is irrelevant. "However, the researchers accept that their study is small and that more work is needed to identify the best ways to remove harmful bacteria by hand washing.
The guidelines of the World Health Organization indicate that we should wash our hands for at least 20 seconds and use enough soap to cover the entire surface of hands. Instructions focus on rubbing hands together in a variety of ways to make sure each surface of each hand is clean.