The Science of Handwashing: Rub, Don't Scrub Hands Raw

Maureen Salamon

March 20, 2020

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

The ubiquitous advice to wash your hands to hinder the spread of COVID-19 has led to a catch-22, dermatologists report: Some clinicians are overdoing it.

The apparent ease with which the virus spreads means that healthcare workers are washing or sanitizing their hands hundreds of times each day. But sometimes they're doing it wrong.

Clinicians are also skipping a crucial step that will protect them from the consequences of these moisture-robbing measures, which have been magnified during the pandemic.

"We shouldn't be washing with harsh soaps over and over again," said Adam Friedman, MD, from the George Washington University School of Medicine and Health Sciences in Washington, DC. "While these will clear any infectious agent from the skin, at the same time, we're destroying the protective barrier that protects us from other pathogens."

"We need to compensate for the damage we're inflicting on our skin with frequent handwashing or alcohol-based hand sanitizers," he told Medscape Medical News. "We don't necessarily need to stop washing our hands as often, but we need to put moisturizer on damp skin to trap water and give our skin what it needs to heal."

Even without soap, water is "probably the number one desiccant that will wash away the moisturizing factors of the skin," Friedman said. "The top layer of the skin, which some consider dead, is actually quite functional."

The stratum corneum breaks down when it senses dehydration, he said. "Those components of the skin are what pull water in from the environment and keep it where it needs to be. When you throw soaps in with charged molecules, called surfactants, they will bind to anything negatively charged, like fats in skin, and rip off the barrier."

Because the pH of skin is acidic and most soaps have a pH higher than 7, they disrupt acid balance in the skin. "Alkaline surfactants will wash away natural moisturizing factors," he said, "which is why frequent handwashing will completely rip up the skin."

And errors in technique add to the inherent pitfalls of constant handwashing.

Rub Palm to Palm, Back to Back of Hands,
Over the Fingers Into the Web Spaces, Around Nails, and Up the Wrists

The biggest mistake is "the super-hot water" many erroneously feel is necessary to leave washed hands germ-free, said Daniela Kroshinsky, MD, from Massachusetts General Hospital in Boston.

Lukewarm water works just as well when combined with soap to remove pathogens, but isn't as likely to cause irritation that leads to chapping and subsequent skin infections, she told Medscape Medical News.

"The perfunctory hand-over-hand motion during washing — rather than systematically going from palm to palm, back to back of hands, over the fingers, in the web spaces, around nails, and up to the wrists" — is also a problem, she explained.

Covering the entire hand is necessary, but there's a fine line between rubbing and scrubbing. Yes to rubbing, but no to scrubbing.

You don't want to scrub because scrubbing will damage the skin barrier and possibly let in germs.

"You don't want to scrub because scrubbing will damage the skin barrier and possibly let in germs," said Carrie Kovarik, MD, from the Perelman School of Medicine at the University of Pennsylvania in Philadelphia. "As physicians, we want to get the germs off, but sometimes the things we do to do that are counterproductive."

"We think the physicality of rubbing the hands together disrupts the adhesion of pathogens more than the soap," Friedman said. "The 20-second rule is somewhat arbitrary, but we need time to physically disrupt anything adhering to the skin. Surfactants in the soap will kill organisms as well."

When you're using hand sanitizer, "make sure you're not putting on just enough to cover your palms," Kroshinsky said. "I've seen people do one pump of sanitizer, and it doesn't usually give you enough. You need a good coating all the way to the wrists."

A moisturizer that contains mineral oil or petrolatum is ideal, as are products you can squeeze from a tube rather than a pump, according to the American Academy of Dermatology. Also, contrary to advice prevalent on social media, moisturizing after cleansing doesn't negate handwashing efforts or create vulnerability to pathogens.

When possible, choose paper towels instead of hand dryers, Kovarik advised. Jet dryers in public bathrooms disperse more than 190 times more virus particles than paper towels, according to a 2018 study.

And then there is the widely disseminated advice to avoid touching our faces to stem the spread of COVID-19. This is so difficult, Friedman explained, because people are more inclined to touch their faces when they are tense.

"There's a subclinical itch associated with stress, which is why people scratch their heads," he said. "Low-level signals prompt stressful behaviors related to the face."

A buddy system might work best to combat this behavior.

"A lot of people don't even realize they're touching their faces," Kroshinsky said. "You can team up with a colleague or loved one to watch each other and remind them when it's happening."

"Make it a competition," Friedman suggested. "We're really bad at change, so having positive reinforcement and constructive feedback is helpful."

American Academy of Dermatology (AAD) 2020 Annual Meeting.

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