ELI5: How does soap actually kill germs?

Soap kills germs by ripping their outer protective skin apart and washing the broken pieces away down the drain.

Imagine a germ, like a virus or a tiny bacterium, as a tiny water balloon. The rubber part on the outside of the balloon is made of fat and oil, and it holds everything inside the germ safe and secure.

Normally, if you only wash your hands with plain water, the water just slides right over the oily germs. You know how oil and water do not mix when you shake up salad dressing? The same thing happens on your skin. Water alone cannot grab onto oily germs.

This is where soap works like a superhero tool with two different hands:

• One hand loves water (water-loving).


• The other hand hates water and loves oil (oil-loving).

Because the soap pushes its way in so strongly, it pops the germ's skin open—just like popping that water balloon with a needle. Once the germ bursts open, all of its insides spill out, and the germ is completely destroyed. It cannot make you sick anymore.

After that, the other hands of the soap (the water-loving ones) grab onto the flowing water from your faucet. They trap the broken bits of dead germs, along with everyday dirt and grease, inside tiny bubble cages. When you rinse your hands, the water sweeps those cages right off your skin and straight down the sink.

This is why doctors always tell you to wash your hands for twenty seconds, or the time it takes to sing "Happy Birthday" twice. The soap needs a little bit of time to find all the germs, pop them open, and help the water wash them away for good.