If health PSAs have taught us anything, it’s that the only way to wash your hands is to make the water scalding hot, scrub, scrub, scrub with plenty of antibacterial soap, and sing “Twinkle Twinkle Little Star” to achieve the requisite 20 seconds of washing time. Well, science has spoken, and that means we have news for you: The water temperature doesn’t matter, and just 10 seconds will do the trick.
In May 2017, a Rutgers University study changed what we knew about washing your hands. Multiple times over a six-month period, the researchers put “high levels of a harmless bacteria” on the hands of 21 participants. Each time, they were asked to wash their hands in water at a temperature of 60 degrees, 79 degrees, or 100s degrees Fahrenheit (that’s 16, 26, and 38 degrees Celsius) using varying amounts of soap.
The results? The volunteers removed roughly the same amount of bacteria, regardless of water temperature. However, there was a marked difference in energy usage. Lead author Donald Schaffner says in a press release, “This study may have significant implications towards water energy since using cold water saves more energy than warm or hot water.” Schaffner also notes that “even washing for 10 seconds significantly removed bacteria from the hands.” You hear that? There’s no need to sing “Twinkle Twinkle Little Star” in public … unless you feel so inclined.
And what about those “varying amounts of soap” we mentioned? While researchers found no significant difference in bacteria reduction between regular and antimicrobial soap, they emphasize that there’s more research to be done. In the name of public health, scientists would love to pinpoint which soap to use and exactly how much to optimally remove harmful bacteria. Until then, just make sure you’re using soap and washing your hands for at least 10 seconds. As for water temperature, you do you! Schaffner insists that “people need to feel comfortable when they are washing their hands.”