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Hand Washing: Cool Water As Effective As Hot For Removing Germs

By Dr. Donald W. Schaffner
August 06, 2018


We all know that washing our hands can keep us from spreading germs and getting sick. But a new study I co-authored with GOJO scientists and published in the Journal of Food Protection found that cool water is just as effective as hot water in removing bacteria from the hands.


People should use a comfortable water temperature when they are washing their hands, but our study shows us that water temperature didn’t matter. The study was conducted by putting high levels of harmless bacteria on the hands of 20 participants’ multiple times over a six-month period. Participants were asked to wash their hands in 60-, 80- or 100- degrees Fahrenheit water temperatures using 0.5 ml, 1 ml or 2 ml volumes of soap, and different lather times.


This study may have significant implications towards water energy, since using cold water saves more energy than warm or hot water.


These findings are important, particularly to the restaurant and foodservice industry. The U.S. Food and Drug Administration issues food safety guidelines to states every four years in the form of the Model Food Code. Those guidelines currently recommend that plumbing systems at food establishments and restaurants deliver water at 100 degrees Fahrenheit for handwashing.


The issue of water temperature has been debated for years with little science to back-up any recommendation to change the policy guidelines or proof that water temperature makes a difference in hand hygiene. Some states, in fact, interpret the FDA guidelines as a requirement that water temperature for handwashing must be 100 degrees.


The FDA is scheduled to hold a conference in 2018 to discuss the existing code and any modifications that should be made, and I would like to see the water temperature recommendations revisited at that time.


This study provides support for a policy change.  Instead of a temperature requirement, I think the recommendation should only say that comfortable water is needed for handwashing. We are wasting energy to heat water that is not necessary.