Warm and cold water, which is better for hand washing?

It’s been longed believed that washing your hands in warm water is more effective at removing germs than cold water. However, a new study is turning that old notion on its head.

According to researchers at Rutgers University, it makes no difference if you wash your hands in hot or cold water as both are equally as effective at removing harmful bacteria.

“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 Donald Schaffner, co-author of the study, in a statement.

In this small study published in the Journal of Food Protection, researchers put high levels of a harmless bacteria on the hands of 21 participants multiple times over a six-month period. They were then asked to wash their hands in 60-degree, 79-degree or 100-degree water temperatures using 0.5 ml, 1 ml or 2 ml volumes of soap.

That’s when researchers also found that washing your hands for only 10 seconds (as opposed to the recommended 15 to 20 seconds) also removed a significant amount of bacteria from the hands.

It also didn’t matter how much soap was used in the cleaning process.

“This is important because the biggest public health need is to increase hand washing or hand sanitizing by food service workers and the public before eating, preparing food and after using the restroom,” co-author Jim Arbogast said.

More research is needed to see if the type of soap one uses also affects the outcome of cleanliness of the hands, the study says.

Schaffner says these findings are significant, especially when it comes to water usage and conservation as using cold water tends to save more energy than warm or hot water.

Despite the study only including a small number of participants, executive director of the Canadian Public Health Association (CPHA) Ian Culbert says it was nonetheless a well-designed study that was still able to offer an interesting perspective on the long-debated issue.

“It’s an interesting piece of information in the overall study of hand washing,” he says. “Does it give us the definitive answer about hand washing? No, I don’t think so, but it is an important piece of the growing evidence [in the debate]. It doesn’t necessarily have strong evidence, because they haven’t done the studies to back it up, but it is still an important piece of developing that evidence so that we know that whatever instructions we are giving is the best possible advice to be giving out.”

As of now, health professionals continue to recommend that people wash their hands in warm water for at least 15 seconds, Culbert says.

“If you think about how many different things you do with your hands and how many different places they may visit in any given day — even if your hands look clean, they are covered in microorganisms or germs, some of which are harmless while others can carry infection and disease,” says Culbert. “But for the time being, I don’t see the recommendations changing but I’m hoping that this study will lead to more in-depth stories that can give us even stronger evidence that could lead us to changing our current recommendations.”

In terms of what type of soap you should be using and how much, Culbert says there is no set recommended amount, but the type of soap may have an impact on how well you clean your hands.

For the most part, Culbert says there is no difference between anti-microbial soaps and “ordinary” soaps, as one has not been proven to be more effective than the other. However, foam soaps are not ideal as they are often diluted from the air that’s injected into the bottles (which is what helps make the soap “foamy”).

“It’s just important to make hand washing part of your everyday routine,” Culbert says. “It is probably the single most effective activity we have to reduce the spread of disease, especially during cold and flu season. And while for you it might not seem like it has a major impact, but for those people around you who may have compromised or weakened immune systems, it could make a big difference.”