How does soap work and is hand sanitiser better?

As people around the world work to slow the spread of the virus called COVID-19, everyone is telling us to wash our hands with soap.

If you’re following this advice from the government, doctors, scientists, teachers and parents, you’ve probably never washed your hands as often or as thoroughly in your life.

But is soap really necessary? Does soap work? How does it work? Can’t you just use water? Is hand sanitiser better?

Not well enough.

Germs such as bacteria and viruses stick to the natural oil (a type of fat) on your skin. Water without soap isn’t very successful at getting the germs off your skin because water and oil don’t mix.

Soap is made with some kind of fat or oil, water and some kind of alkaline* substance, such as a type of salt. It sometimes also has small quantities of other things in it, such as perfumes or colours.

Ancient humans were making soap thousands of years ago using animal fat and wood ash, which is the alkaline ingredient. When the fat and the alkaline ingredient are mixed together with the help of some water, there is a chemical reaction, called saponification. Soap is the result!

The molecules* of soap, incredibly, have one end that loves water and one end that loves oil.

If you wash your hands with soap, the soap molecules act as a link between the water you’re washing with and the oil on your skin. A molecule of water joins to one end of the soap molecule and a molecule of oil joins to the other end.

When you rinse your hands, the whole lot washes off, lifting the oil off your skin and taking the germs with it.

Also, scientists have looked at particles of COVID-19 virus under a microscope and know it is what is called an “envelope virus”, which means each particle has a coating of fat molecules around it. When you wash your hands with soap, the coating falls apart, destroying the virus particle.

Parents clueless about preventing colds in kidsSylvie and brother Curtis washing their hands with soap. Picture: Tim Carrafa

Germs love damp environments, so drying your hands is important. Disposable paper towel or a hand dryer is best if you are in a public bathroom.

Many hand sanitisers are made with a type of chemical called ethanol, a form of alcohol. To kill germs such as viruses, the hand sanitiser has to have a minimum of around 60 per cent alcohol in it. The alcohol can kill virus particles much like soap does, but you have to soak every part of your hands thoroughly with the sanitiser. For this reason, a squirt of sanitiser gel or a wipe may not be thorough enough.

If it isn’t possible to wash your hands with soap and water, hand sanitiser is useful.

For more information on hand washing visit

Leave a Reply