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Why wash your hands for 20 seconds?

Studies show that thorough handwashing takes at least 20 seconds. Here's why.

ATLANTA — Washing your hands for 20 seconds can seem like a long time, enough time to wonder why 20 seconds became the rule.

It’s roughly the amount of time it takes you to sing the alphabet or hum "Happy Birthday" twice. The coronavirus pandemic has taught us about the importance of thorough handwashing and the recommendation to wash for at least 20 seconds.

Emory University’s Dr. Karen Levy says the 20-second rule has been around for so long, no one questions it.

“Who’s going to come back and say well, it’s only 15 seconds?” says Dr. Levy.

The CDC says the time you need to wash thoroughly depends on how dirty you are. You may need more than 20 seconds.

“The optimal length of time for handwashing is also likely to depend on many factors, including the type and amount of foil on the hands,” reads the CDC website. “Evidence suggests that washing hands for about 15-30 seconds removes more germs from the hands than washing for shorter periods.”

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According to Thomas Gilbert, a chemistry professor at Northeastern University, soap needs time to trap, dissolve, then carry dirt and viruses away from your hands and down the drain.

“Your hands have many surfaces and parts to clean, and the lather needs to cover all of them to capture the germs within,” says Gilbert. “If you’re doing it right, 20 seconds allows enough time to be thorough and for soap molecules to do their job on the entire hand.”

RELATED: Why washing your hands well is so important to protect your family from the flu

Dr. Levy says there are plenty of places for germs to hide.

“The important thing is that you’re thorough about washing in-between your fingers,” says Dr. Levy. “Get underneath your fingernails. If you can accomplish that in 15 seconds, more power to you.”

Whether it’s singing a song or watching a clock, think 20 seconds when your hands are lathered with soap.

11Alive is focusing our news coverage on the facts and not the fear around the virus. We want to keep you informed about the latest developments while ensuring that we deliver confirmed, factual information.

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