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Is Using Hot Water for Washing Hands More Effective Than Using Cold Water

  • Synopsis: Published: 2017-06-01 - Study reveals that when washing hands cool water removes the same amount of harmful bacteria as warm or hot water. For further information pertaining to this article contact: Rutgers University at

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Quote: "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..."

We all know that washing our hands can keep us from spreading germs and getting sick. But a new Rutgers-New Brunswick study found that cool water removes the same amount of harmful bacteria as hot.

"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, distinguished professor and extension specialist in food science.

In the Rutgers study, published in the June issue of the Journal of Food Protection, high levels of a harmless bacteria were put on the hands of 21 participants multiple times over a six-month period before they were 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.

"This study may have significant implications towards water energy, since using cold water saves more energy than warm or hot water," said Schaffner. "Also we learned even washing for 10 seconds significantly removed bacteria from the hands."

While the study indicates that there is no difference between the amount of soap used, more work needs to be done to understand exactly how much and what type of soap is needed to remove harmful microbes, said co-author Jim Arbogast, vice president of Hygiene Sciences and Public Health Advancements for GOJO.

"This is important because the biggest public health need is to increase handwashing or hand sanitizing by foodservice workers and the public before eating, preparing food and after using the restroom," Arbogast said.

These findings are significant because the U.S. Food and Drug Administration issues guidelines, every four years, to states. The guidelines currently recommend that plumbing systems at food establishments and restaurants deliver water at 100 degrees Fahrenheit for handwashing.

Schaffner said the issue of water temperature has been debated for a number of years without enough science to back-up any recommendation to change the policy guidelines or provide proof that water temperature makes a difference. Many states, in fact, interpret the FDA guidelines as a requirement that water temperature for handwashing must be 100 degrees, he said.

"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," Schaffner said.

Video Clip: Washing Your Hands with Cold Water is Just as Effective as Warm

The authors literature review suggests there is little or no evidence suggesting hygienic benefits of using warm or hot water to wash hands.Therefore, due to the growing cost of energy and growing interest in energy conservation, the authors sought to investigate whether the energy used to wash your hands with hot or warm water was necessary.

Facts: Handwashing

  • There are 5 critical times during the day where washing hands with soap is important to reduce fecal-oral transmission of disease: after defecation, after cleaning a child's bottom, before feeding a child, before eating and before preparing food or handling raw meat, fish, or poultry.
  • Excessive hand washing is commonly seen as a symptom of obsessive-compulsive disorder (OCD).
  • After washing and drying hands with a warm-air dryer, the total number of bacteria was found to increase on average on the finger pads by 194% and on the palms by 254%.
  • As a general rule, hand washing protects people poorly or not at all from droplet and airborne diseases, such as measles, chickenpox, influenza, and tuberculosis.

Related Information:

  1. Hospital Hand Washing Leads to Rise in Dermatitis - Incidence of dermatitis increased in health care workers following hand hygiene drive to reduce infections such as MRSA - University of Manchester
  2. Health Workers Exposed to Unsafe Triclosan Levels in Antibacterial Soap - Hand-washing with antibacterial soap exposes hospital workers to significant and potentially unsafe levels of triclosan - University of California - San Francisco
  3. Tackling Hospital Superbugs with Groundbreaking Irisys Infrared Technology - Figures show that about nine per cent of patients actually acquire infections during a hospital stay - Irisys

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