Because soap really does work best, we continue to hear the medical profession instructing we wash our hands with warm water and soap.

But how can your grandmother’s soap—that ancient and simple human technology—work so well?

What is a lipid? A lipid is a substance that repels water, the way a great raincoat repels water. Fats—all of the types of fat you can think of—are lipids. Lipids stick together and make impenetrable stuff like you find baked onto your casserole dish.

What’s in soap? Some of the molecules in soap are surfactants. Surfactants are certain molecules which actively separate lipids. Surfactants separate lipids the way bouncers break up bar fights: They forcefully insert themselves and separate the individual lipids. That’s why soaking your casserole dish in soap and water magically turns the impossibly-baked-on gunk into easily-rinsed-away gunk.

How are lipids relevant to viruses? Viruses have an outer envelope—imagine a rain coat shaped into a beach ball—that surrounds and protects the contents of the virus. That outer envelope is made from lipids. It’s tough like the baked-on-gunk on a casserole dish is tough.

What’s inside a virus particle? Viruses contain a long string of instructions. Your cells contain your personal set of instructions, called your DNA. Viruses contain a set of instructions similar enough that your cells can follow those instructions. When a virus’s instructions get into your cell, the cell is duped into making more viruses rather doing whatever it normally would do.

What does soap do to the lipid envelope of a virus? It does the same thing soap and warm water do to the crud stuck on your casserole disk. Soap makes the lipid envelope fall apart, exposing the virus’ payload of instructions.

What happens to the virus’ instructions without the protective lipid envelope? The instructions are quickly damaged and made useless. The instructions in the virus are extremely delicate. Exposure to oxygen, (1/5 of our atmosphere is Oxygen,) or light, (we have a lot of that too,) or several things found in soap, will quickly destroy the instructions. The DNA in your cells is just as delicate, but your cells have structures and processes to protect and repair your DNA. But unlike your cells, viruses are very simple; all they have protecting their instructions is a lipid envelope wrapped around the outside.

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