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Do You Really Need to Wash Your Hands for 20 Seconds?

Absolutely, washing your hands for 20 seconds is essential. This duration ensures you thoroughly clean all surfaces, effectively removing germs that can cause illness. It's about more than just a quick rinse; it's a simple yet powerful act to protect your health. Wondering what makes those 20 seconds so crucial? Let's examine the science behind it.
Margaret Lipman
Margaret Lipman
Margaret Lipman
Margaret Lipman

For months, public health authorities around the world have been instructing us to wash our hands to prevent the spread of Covid-19. Chances are, you've seen posters specifying 20 seconds as the amount of time you should spend at the sink.

But why 20 seconds? And is it really necessary to spend that long washing your hands? According to new research published last month in the journal Physics of Fluid, the answer to the second question is a resounding "yes." Using mathematical modeling, the researchers determined that 20 seconds is required to dislodge the viral and bacterial particles that are attracted to our hands. Furthermore, moving your hands more vigorously provides the right amount of force to allow particles to escape into the running water.

Mathematical modeling proves that 20 seconds of hand washing is required to dislodge viral and bacterial particles.
Mathematical modeling proves that 20 seconds of hand washing is required to dislodge viral and bacterial particles.

The Centers for Disease Control (CDC) has long recommended washing your hands with soap and water for 20 seconds, but their recommendation was based on the link between how many microbes remain on your hands and how long you spend washing them. In contrast, this study used physics to examine how much energy is needed to overcome the attractive forces keeping germs on our hands.

Don't forget to wash your hands!

  • Interestingly enough, the study did not account for using soap, which plays a dual role in helping remove viral and bacterial particles, and also destroying their outer membranes.

  • The CDC recommends singing the "Happy Birthday" song twice in order to reach the 20 second mark.

  • According to the CDC, hand washing with soap could reduce the number of people getting sick with diarrhea by up to 40%.

Margaret Lipman
Margaret Lipman
Margaret Lipman is a teacher and blogger who frequently writes for WiseGEEK about topics related to personal finance, parenting, health, nutrition, and education. Learn more...
Margaret Lipman
Margaret Lipman
Margaret Lipman is a teacher and blogger who frequently writes for WiseGEEK about topics related to personal finance, parenting, health, nutrition, and education. Learn more...

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    • Mathematical modeling proves that 20 seconds of hand washing is required to dislodge viral and bacterial particles.
      By: Lasse Kristensen
      Mathematical modeling proves that 20 seconds of hand washing is required to dislodge viral and bacterial particles.