Why does good hand washing work to prevent the spread of germs?

Staying Safe

Q: It’s just soap and water, right?

A: Soap and water work together to create a matrix that germs cannot escape.

When we wash our hands with soap for 20 seconds, soap molecules trap viruses, bacteria, and debris. Water rinses the matrix of soap and germs away from your skin. Hand sanitizer that is 60% alcohol rubbed on your hands for 20 seconds destroys the outer protective layer of germs as well.

It is amazing to think that something as simple as hand washing can stop the spread of disease and save lives. Long before Louis Pasteur’s germ theory, Dr. Ignác Semmelweis was laughed at and scorned in 1847 when he proposed physicians wash their hands AFTER leaving the morgue and BEFORE going to deliver babies. He was an obstetrician in a Vienna hospital that had a high incidence of maternal death from an infection called “childbed fever”. When the practice of hand washing was finally adopted, maternal death rates went from 18% to 1%. Why? Because soap kills germs.

Some viruses, bacteria, and dirt have a fatty outer layer called lipids. A basic soap molecule is polar: one end is attracted to lipids, the other is attracted to water. When exposed to soap, a germ’s protective layer splits and sticks to one end of the soap molecule. The other end of the soap molecule clings to water. The matrix of soap and germs is called a micelle. They are rinsed away from the skin with water.

It takes time for the micelles of soap and germs to develop. So washing your hands for 20 seconds (even when using hand sanitizer) is essential. Hand sanitizer that is made of at least 60% alcohol will destroy lipid layers as well. But that is a dialogue for another day.

This is the best practice for hand washing:

1. Wet your hands with clean, running water (hot or cold) and apply soap.

2. Work up a lather by rubbing your hands together, washing the backs of your hands, between your fingers, and under your nails.

3. Scrub your hands for at least 20 seconds. To mark time, hum the traditional “Happy Birthday” song from beginning to end twice. Or sing Stevie Wonder’s “Happy Birthday” chorus six (6) times.

4. Rinse your hands well under clean, running water. This is not part of the 20 seconds.

5. Turn off the water with your elbow or drying towel if possible.

6. Dry your hands using a clean towel.

Hand dryers are not recommended to help you stop the spread of germs. For a Myth Buster reality check, see the video linked below.

There are a lot of ideas about best practices. The tips listed here will keep you, your family, friends, and even strangers safe.

CDC When and How to Wash Your Hands


Hand sanitizer

Myth Busters hand drying episode

Dr. Ignác Semmelweis

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