The science behind soap, and why it’s better than hand sanitizer

Since the COVID-19 (coronavirus) global pandemic spread to the United States (and even before then), people have been stocking up on hand sanitizer. It’s been nearly impossible to find on any shelves in stores, or even online.

But people are filling their carts with the wrong product. They should be buying soap, which does a much better job of actually getting rid of the virus on your hands.

“Ordinary soap is highly effective at reducing exposures to harmful or pathogenic microbes,” says environmental epidemiologist Irva Hertz-Picciotto, Ph.D., M.P.H., director of the National Institutes of Health–funded Environmental Health Sciences Center at the University of California, Davis.

Here’s the deal: Hand sanitizer that contains at least 60 percent alcohol does knock out the harmful germs contained in the coronavirus—but it still leaves virus residue on your hands. On the other hand, using soap and water has nifty molecules that send the nasty stuff down the drain. 

The Amazing Science of Soap

Soap molecules have two ends: one that attaches to the coronavirus, which has a lipid membrane (a fatty outer shell), and one H₂0-loving end that water attaches to.

So, when you wash your hands, the soap latches onto the virus, the water grabs ahold of the suds, and both are washed down the sink. Cool, right?

Keep in mind that for all of this to work, you need to spend at least 20 seconds washing, according the Centers for Disease Control and Prevention (CDC). Scrubbing is key, because it creates enough friction to lift the germs off of your skin and out from under your nails. You can learn more about proper handwashing techniques here.

Something You Might Not Know About Hand Sanitizers

Antibacterial products, including hand sanitizers, are good at doing what they promise to do—killing up to 99 percent of bacteria. But they get rid of good bacteria along with the bad stuff.

“Most people believe that all bacteria are bad, period, and that the goal is to eliminate or minimize all exposures,” Hertz-Picciotto says, noting that this isn't true, and that exposure to some bacteria enables us to function. Good bacteria can help with things like digestion and nutrient absorption, she says.

On the other hand, regular soap is selective about the kinds of bacteria it washes away: It removes the bad stuff but leaves the good bacteria unharmed.

The caveat here is that hand sanitizers are a critical tool for doctors, nurses, emergency workers, and other medical personnel, according to the CDC. The rest of us? Not so much.

Exception! The One Time to Use Hand Sanitizer

All that said: If you’re in a setting where sinks, soap, and clean water aren’t nearby, hand sanitizer is absolutely better than nothing, notes the CDC.

To get the most benefit: Choose one that is at least 60 percent alcohol, use a generous squirt, and rub the gel all over the surfaces of your hands until they’re dry.

The information in this story is accurate as of press time and posting. Because the situation surrounding COVID-19 continues to evolve, we encourage readers to follow the news and recommendations for their own communities by using the resources from the CDC, WHO, and their local public health department.