Washing your hands sounds trivial—here’s the science behind why it works

As COVID-19 and influenza continue to spread across the country, everyone from coworkers to the CDC wants you to wash your hands. While hand sanitizer is a good option, it’s still second to good old fashioned hand washing.

“There’s really no substitute for controlling the spread of viruses to hand washing—nothing we do is going to work as well as that,” says  Russell Buhr, MD, PhD, a pulmonary and critical care physician at UCLA Medical Center. “When you look at it historically, it used to be that infant mortality was a huge problem, right? A lot of it was because people weren’t appropriately doing hand washing, because we didn’t understand what germs were and how they worked.”

Why is washing your hands so effective? “Some of its mechanical, the act of scrubbing and rinsing that stuff off is carrying the dead virus away,” says Dr. Buhr. “We know that soap helps break down the viruses, because soap works by dissolving fats and lipids and so the viruses are surrounded in a lipid shell.” He says soap chemically destroys the virus.

“Sounds banal, but soap really is an amazing weapon that we all have in our homes,” says Karen Fleming, PhD, a scientist and professor at Johns Hopkins University, on Twitter. “This is because coronavirus is an ‘enveloped’ virus, which means that it has an outer lipid membrane layer. Washing your hands with soap and water has the ability to ‘dissolve’ this greasy fatty layer and kill the virus.”

The number one reason people get sick isn’t because someone coughed in their face, says Dr. Buhr, it’s because someone sneezed in their hand and then opened a door, the next person touched the door handle, and then touched their eyes, nose, or mouth. In operating rooms, the most important thing health-care workers do to protect their patients is washing their hands. “We still wear gloves, and sterile gowns, and masks, and hats, and all that stuff,” he says, “but that’s a secondary to good hand washing.”

To ensure you’re getting your hands super clean, Dr. Buhr recommends washing your hands with the hottest water that you can tolerate without about burning yourself and soap for between 30 and 45 seconds—the time it takes to sing the alphabet twice. “And then as you’re leaving the bathroom, if you dry your hands with paper towel, then keep that paper towel in your hand and use it to open the door, and then throw the paper towel away after so you don’t immediately pick up more germs from your colleagues who maybe weren’t as good a citizen as you and didn’t wash their hands,” he says.

Hand sanitizer works well, he says, but doesn’t accomplish all of those things. “In a pinch, hand sanitizer is certainly better than nothing, the alcohol will still destroy the outside of the virus and that will help dry it out and kill it, but we still encourage people to wash their hands regularly to eliminate the residue of the hand sanitizer and whatever dead pathogens and dirt and grime is just sitting on our hands,” says Dr. Buhr.

Not all hand sanitizers are created equal—here’s what germ experts want you to know. And this this free online course will give you all the education you need on COVID-19.