The Exact Science Behind Why You Have To Wash Your Hands For At Least 20 Seconds

A person lathers their hands with soap. You've heard that washing your hands for 20 seconds is impor...
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It's one of the most common things to hear amidst the coronavirus pandemicwash your hands with soap and water for 20 seconds. This is one of the Centers for Disease Control and Prevention's (CDC) main recommendations for killing germs. But the question remains: why should you wash your hands for 20 seconds, specifically?

"Washing your hands for at least 20 seconds is the most effective way to ensure your hands aren’t spreading pathogens," says family physician Dr. Natasha Bhuyan, MD. "This is in two ways: it helps both wash away dirt and grime and germs, but also helps kill pathogens."

Sure, but why two rounds of "Happy Birthday" instead of one? "Determining the optimal length of time for handwashing is difficult because few studies about the health impacts of altering handwashing times have been done," the CDC wrote on its site. "Of those that exist, nearly all have measured reductions in overall numbers of microbes, only a small proportion of which can cause illness, and have not measured impacts on health. ... Nonetheless, evidence suggests that washing hands for about 15-30 seconds removes more germs from hands than washing for shorter periods."

According to a paper presented at the 2012 International Association for Food Protection, study participants who washed their hands for 20 seconds reduced the number of bacteria significantly more than those who washed for only five seconds. A similar 2008 study published in the journal Applied and Environmental Microbiology found that making sure your hands are fully lathered in soap and washing for close to 30 seconds was much more effective at lowering bacterial levels on your hands than washing for closer to 15 seconds.

If you're trying to figure out how to most effectively get to 20 seconds without counting or staring at a clock, Twitter has some fun ideas for you. A popular Tweet from user @TheOtherTracy suggests singing "Welcome to the Black Parade" from "When I was" to "the beaten and the damned." Other suggestions include the chorus of The Killers' "Mr. Brightside" or Fleetwood Mac's "Landslide," if you want to bum yourself out. This meme generator will also pop your favorite song onto a hand-washing diagram, in case you want other suggestions.

Dr. Buyhan also tells Bustle that it's not just the length of time you spend washing. It's also about the quality of the wash itself. "Often, germs are hiding in places that we don’t always clean thoroughly, such as under our fingernails or even the backs of our hands," she says." Be sure to pay attention to those spots. Also, use a paper towel when turning off a faucet handle — you don’t want to undo all your hard work!"

Make sure you're getting those soapy seconds in. It'll help keep you and the folks closest to you illness-free.

Studies Referenced:

Jensen, D. (2012) Efficacy of handwashing duration and drying methods. International Association for Food Protection,

Fuls, J.L. (2008) Alternative hand contamination technique to compare the activities of antimicrobial and nonantimicrobial soaps under different test conditions. Applied and Environmental Microbiology,


Dr. Natasha Buyhan, MD, One Medical