Health / Microbiology / Science

Soap versus virus

When it comes to avoiding the latest cold going round the office, a lot of people swear by hand sanitisers. The humble hand soap is such a staple that people skip right over it in considering fighting germs: sure, it cleans your hands, but will it kill a virus?! How could it, it’s only soap!

The truth is that soap is probably better than an alcohol-based hand sanitiser. If you don’t have access to soap and water, then a hand sanitiser with at least 60% alcohol isn’t a bad substitute, but the best thing to do it just to thoroughly wash your hands. The thing people don’t realise is that it’s not just washing away the viruses: soap actually helps to break down viral particles, as much or better than alcohol does.

How does that work? Well, the DNA or RNA of viruses can be surrounded in a sort of wrapper made of lipids and protein, and this is true of influenzaviruses (which cause flu) and some of the causes of the common cold (like coronaviruses, of which SARS-CoV-2 is simply one, with others causing mild infections). This lipid/protein layer protects the genetic material inside.

Lipids are fats, so think about the way dish soap handles that greasy oven tray: just running water over it doesn’t do a lick of good, because fats don’t mix with water. Soap (or at least, constituents of soap, like sodium laureth sulphate) is an “amphiphile”. That means it has a region which is “lipophilic” (literally, “fat loving”) and a region which is “hydrophilic” (“water-loving”). When you mix an intact viral particle with soap, the soap attaches to the lipids in the wrapper around the virus, pulling the wrapper apart. That makes the virus soluble in water, and no longer able to infect human cells!

So every time you wash your hands for 20 seconds with a good handful of soap, you’re not just washing away potential infectious particles: you’re actually killing the virus. Just don’t forget to moisturise as well — soap strips natural, beneficial fats from your skin as well, which normally form a protective layer that keeps your skin healthy!

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