How Long Should You Wash Your Hands To Kill Germs?

You know the basics: Use soap and water, and scrub for the length of the “Happy Birthday” song as you wash your hands. Those simple steps can help prevent the common cold, flu, and some other icky illnesses.

Yet one survey this year confirmed what we all suspected: Only two-thirds of respondents said they always washed up after using the bathroom. And even if you do, believing these misconceptions may leave you with germs on your hands. Read on to find out if everything you think you know about washing your hands is fact or myth.

“Our research showed that there’s no difference in cleaning power whether the water is 60°F (that’s cold), 80°F (pretty comfortably warm), or 100°F,” says microbiologist Donald Schaffner, PhD, professor of food science at Rutgers University. If you can tolerate hot water for only three seconds, it’s completely OK to switch to a cooler temperature so you can keep your hands in the H2O longer—it’s the time they spend under the faucet that really matters, says Schaffner. How long should you wash your hands? His lab tested washes of different lengths and found that 20 seconds was more effective than five seconds, so go for at least 20.

Final answer: false

If your hands are visibly dirty, old-school soap and water is the way to go, because the action of rubbing and rinsing dislodges bacteria and viruses. “Hand sanitizers must contact germs to damage and kill them,” and dirt can be a barrier, says David Berendes, PhD, MSPH, epidemiologist with the Waterborne Disease Prevention Branch of the Centers for Disease Control and Prevention (CDC).

But if soap and water aren’t available and your hands aren’t filthy, does hand sanitizer work? Yes, an alcohol-based sanitizer that contains at least 60 percent alcohol can do the trick in a pinch. Cover all surfaces of your hands, and keep rubbing until they’re dry (don’t wipe it off). We like these travel-sized bottles of Purell so you can take it with you on the go.

Final answer: True, but hand sanitizer isn’t useless.

Quickly sticking your hands under the tap removes a lot of bacteria—maybe as much as 90 percent. But although that might sound good enough, a rinse still leaves you pretty germy, explains Schaffner, considering that your hands can be contaminated with millions of pathogens (a single gram of poop can contain one trillion germs!) and even one microorganism can cause illness.

Final answer: false

That soft, gooey bar soap may look as if it’s hosting a germ field day. Yet one widely cited (albeit industry-sponsored) study found that when researchers implanted germs in softened bar soaps, none of those germs clung to hands after washing. The CDC says it doesn’t matter if you use liquid or bar soap at home or in public places—both do the job, as does foam soap, an aerated version of the liquid variety. Overall, any soap is better than none.

Final answer: false

A recent study from UConn Health found that after people held clean hands under a dryer for a minute, new bacteria could wind up on hands. The dryers stir up bacteria already in the bathroom, depositing some of it on once-clean mitts. But don’t freak out: Although people undergoing cancer treatments and the elderly need to be careful, “the vast majority of bacteria are not likely to be harmful to someone with a working immune system,” says study coauthor Thomas Murray, MD, PhD, of the division of infectious disease and immunology at Connecticut Children’s Medical Center. Bottom line? If there’s a towel option, that’s a good first choice.

Final answer: true