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Study: Washing your hands — even without soap — is more effective than hand sanitizers for flu prevention

The reason: When wet mucus surrounds the virus, it acts as a protective hydrogel, keeping the disinfectant from reaching and killing the germs.

washing hands
When you wash with running water, the rubbing action of your hands removes the mucus surrounding the virus and washes the virus down the drain.
Photo by Curology on Unsplash

Washing your hands under running water — even without soap — is more effective at stopping the spread of flu germs than using ethanol-based hand sanitizers, according to Japanese researchers.

The reason: When wet mucus surrounds the virus, it acts as a protective hydrogel, keeping the disinfectant from reaching and killing the germs. But when you wash with running water, the rubbing action of your hands (if you do it thoroughly) removes the mucus and washes the virus down the drain.

The authors of the study, which was published earlier this week in the journal mSphere, say they were somewhat surprised by their results. Previous studies have suggested ethanol-based sanitizers are effective against flu viruses.

“We had predicted that the virus in mucus would be somewhat resistant to alcohol disinfectants,” said Dr. Ryohei Hirose, the study’s lead author and a molecular gastroenterologist at Kyoto Profectural University of Medicine, in an interview with Healthline. “However, we found that the protective effect of mucus is stronger than expected and there may be room for improvement in current hand hygiene guidelines.”

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Most of the earlier studies, Hirose and his co-authors point out in their paper, were conducted using virus-containing solutions that had already dried. In those studies, the disinfectant was able to reach and inactivate the virus within half a minute or so.

How the study was done

The new study involved a series of tests in which Hirose and his colleagues took sputum (a mixture of coughed-up saliva and mucus) from people infected with influenza A virus (the most common type of flu virus) and put it on the fingertips of 10 volunteers.

“We aimed to reproduce the situation in which infectious mucus discharged from [flu-infected] patients adheres to the fingers of medical staff,” they explain.

The researchers then applied a hand sanitizer to the volunteers’ fingers — either after the mucus completely dried (a process that took about 40 minutes) or while it was still wet.

When the mucus was dry, the sanitizer took about 30 seconds to inactivate the virus. When the mucus was wet, however, it took eight times longer — about four minutes.

In contrast, when the volunteers washed off the mucus by rubbing their hands together under running water — without soap — the flu virus was eradicated within 30 seconds, regardless of whether the mucus was dry or wet.

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These findings raise concerns about current hand-hygiene practices in hospitals and doctor clinics, which rely heavily on hand sanitizers.

As Hirose and his co-authors point out, “In a realistic medical setting, a sufficient time interval cannot be secured between treatments, and the next patient’s treatment is performed immediately after the current patient’s treatment in many cases.”

The researchers say they hope their findings will be used to develop more effective approaches to hand hygiene and infectious-disease prevention.

How to wash your hands

The publication of this study comes at the start of a new flu season. Its findings are a good reminder that keeping your hands clean is one of the most effective preventive steps you can take to avoid both “catching” the flu and spreading it to others. (The most effective step is to get this year’s flu vaccine.)

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The Centers for Disease Control and Prevention (CDC) recommends that you follow these five simple steps when washing your hands:

• Wet your hands with clean, running water (warm or cold), turn off the tap, and apply soap.

• Lather your hands by rubbing them together with the soap. Be sure to lather the backs of your hands, between your fingers, and under your nails.

• Scrub your hands for at least 20 seconds. Need a timer? Hum the “Happy Birthday” song from beginning to end twice.

• Rinse your hands well under clean, running water.

• Dry your hands using a clean towel or air dry them.

And if you don’t have clean running water? Then, yes, use a hand sanitizer, the agency says. Make sure you rub it all over your hands, and keep rubbing until your hands are dry.

FMI: You can read the new study on the website for mSphere, which is an open-access journal published by the American Society for Microbiology. For the CDC’s scientific rationale behind its tips for washing hands, go to that agency’s website.