Cold Water Washes Hands As Well As Hot, Study Says

Washing our hands frequently and well is one of the best preventive health practices we have, with benefits ranging from protecting us from the common cold and slowing the spread of deadly antibiotic-resistant infections. But despite the strong consensus in the medical community about the benefits of hand washing, there's still a lot we don't know about how to best deploy this potentially life-saving habit.

A new study from Rutgers University casts doubt on one of the most oft-cited hand-washing tips: Hotter water is better. In fact, the study published in the Journal of Food Protection suggests the temperature of the water doesn't seem to affect the amount of bacteria removed at all.

"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," said study author Donald Schaffner, professor and extension specialist in food science.

Previous studies have supported this conclusion.

The matter may be seem trivial, but aside from the general health benefits of hand washing, experts care especially about the practices of food service and preparation staff. Having specific, evidence-based information about how to best wash hands can improve guidelines for these workers and reduce the spread of disease and other contaminants.

"This is important because the biggest public health need is to increase handwashing or hand sanitizing by food service workers and the public before eating, preparing food and after using the restroom," said co-author Jim Arbogast, vice president of Hygiene Sciences and Public Health Advancements for GOJO Industries, a producer of hygiene products.

To conduct the study, the researchers recruited 20 subjects who washed their hands under experimental conditions multiple times over six months. Researchers applied a benign strand of E. Coli to the subjects' hands and measured the effect of the hand washing on the bacteria.

While there were significant differences between the individuals' hand-washing technique and effectiveness, varying the temperature of the water used from between 60 degrees to 100 degrees made no difference. The U.S. Food and Drug Administration has previously issued guidelines requiring restaurants provide 100 degree water for hand washing.

Regular soap performed just as well as antibacterial soaps, which the government believes may pose risks to public health.

Spending more time lathering up the hands, however, was found to make the hands cleaner and most effectively get rid of the bacteria.

"I think this study indicates that there should be a policy change," said Schaffner. "Instead of having a temperature requirement, the policy should only say that comfortable or warm water needs to be delivered. We are wasting energy to heat water to a level that is not necessary."

Read the study's abstract.

Photo credit: Cade Martin, Dawn Arlotta, USCDCP