A common question that tends to be asked about hand sanitisers is, well how do they actually work? And it’s a very good question. Many of us just trust that it works without really knowing anything about what this product does for our hygiene.

So, we’ve looked at the science so that you don’t have to, and answered some key questions.

How does alcohol kill germs?

The key ingredient in most hand sanitisers is alcohol, and this is what kills germs. Like all living things, germs are formed of cells and these cells contain proteins, which are essential to the function of cells and life. So, what alcohols do is break apart these proteins, which splits up the cells or disrupts their process - causing them to die.

How much alcohol is needed for this to happen?

The higher the concentration of the alcohol in sanitisers, the higher the effectiveness of killing germs, including killing a wider variety of germs. Plus, it actually works faster as the concentration of alcohol increases.

Does it kill all types of germs?

No. There are some germs that hand sanitiser isn’t effective against, for example: germs that cause norovirus. Hand sanitiser also doesn’t get rid of things like pesticides, heavy metals, or dirt. So, we should still be prioritising washing our hands with soap and water when possible.

Does hand sanitiser expire?

No, it doesn’t expire. However, most products have to list an expiration date for legal reasons, so you may find a date on your sanitiser. But alcohol is a relatively stable chemical, so if kept sealed and at room temperature, it will stay at the same concentration for a rather long time.

But it is worth noting that alcohol evaporates very easily. So, as you open and close your sanitiser, the alcohol will evapourate over time, and the concentration will decrease.

What about alcohol-free sanitiser?

These sanitisers usually contain benzalkonium chloride instead of an alcohol like ethanol or isopropanol. And they tend to work in a similar way to their alcohol counterparts. However, the science around alcohol-free sanitisers is varied, with many studies finding that it isn’t as effective as an alcohol based sanitiser. It doesn’t kill as many germs, and may only reduce the growth of these germs rather than completely eliminating them.

So, even though alcohol free sanitisers do have some effect, it is still recommended that we use hand sanitiser with at least 60% alcohol content.