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Washing Your Hands Is Important Because Soap “Absolutely Annihilates” Coronavirus

posted by Jason Kottke   Mar 13, 2020

The number one recommendation on the list of protective measures for COVID-19 from both WHO and the CDC is to regularly wash your hands. The CDC in particular recommends hand-washing over using hand sanitizer.

Wash Hands

Vox recently talked with chemistry professor Palli Thordarson about why washing with soap is so effective when dealing with coronaviruses.

The soap takes care of the virus much like it takes care of the oil in the water. “It’s almost like a crowbar; it starts to pull all the things apart,” Thordarson says.

One side of the soap molecule (the one that’s attracted to fat and repelled by water) buries its way into the virus’s fat and protein shell. Fortunately, the chemical bonds holding the virus together aren’t very strong, so this intrusion is enough to break the virus’s coat. “You pull the virus apart, you make it soluble in water, and it disintegrates,” he says.

Then the harmless shards of virus get flushed down the drain. (And even if it the soap doesn’t destroy every virus, you’ll still rid them from your hands with soap and water, as well as any grease they may be clinging to.)

And why do you need to wash for 20 seconds? Because that gives soap time to do its work.

First off, your skin is wrinkly, and it takes time for soap to penetrate into all the tiny folds and demolish the viruses that lurk within. Then the soap needs a few moments to do its chemical work. “You do need a bit of time for all the soap to interact back and forth with the virus particle,” he says. Twenty seconds should do the trick just fine.

See also Why Soap Works from the NY Times, which explains why soap & water is better than hand sanitizer in these cases:

On the whole, hand sanitizers are not as reliable as soap. Sanitizers with at least 60 percent ethanol do act similarly, defeating bacteria and viruses by destabilizing their lipid membranes. But they cannot easily remove microorganisms from the skin. There are also viruses that do not depend on lipid membranes to infect cells, as well as bacteria that protect their delicate membranes with sturdy shields of protein and sugar. Examples include bacteria that can cause meningitis, pneumonia, diarrhea and skin infections, as well as the hepatitis A virus, poliovirus, rhinoviruses and adenoviruses (frequent causes of the common cold).

Update: Thordarson also wrote an article for The Guardian on how effective soap is at killing coronavirus.