Warming up to handwashing

Dear Lucy: Sometimes I see “how to handwash” posters that say to use warm, not hot, water when washing your hands. What do they mean by “warm”? Is there a medically significant difference between hot, warm, and cold water? Or do they really just want you to use water that is comfortable to the touch for the recommended amount of time? —Washing And Wondering

Dear W&W: With cold and flu season upon us, this is a timely question indeed! And Lucy knew just where to go for a quick answer—our very own Howard Heller, associate medical director and infectious disease specialist.
Heller confirms your suspicion that the comfort is the motivation for the “warm water” recommendation. “Studies have shown that water temperature does not affect microbe removal,” Heller says. “What’s important is the length of time spent scrubbing your hands. At least 20 seconds is recommended, and warm water makes that more likely to happen than cold or hot.”
For more information, Heller recommends a visit to the CDC’s handwashing page, where you can watch a video showing you exactly what you should be doing during those 20 seconds and learn more about the science behind those hand-washing recommendations. 
Most importantly, Lucy reminds you and everyone else that good hand hygiene is the key to staying healthy during the winter months and throughout the year. And 20 seconds? It’s about the length of time it takes to sing the “Happy Birthday” song from beginning to end twice—though you might want to do it silently.
Here’s to warm water, clean hands, and good health! —Lucy

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