The Science of Soap: How It Kills the Coronavirus

Palli Thordarson, chemistry professor at the University of New South Wales, writing for The Guardian:

Viruses can be active outside the body for hours, even days. Disinfectants, liquids, wipes, gels and creams containing alcohol are all useful at getting rid of them — but they are not quite as good as normal soap.

When I shared the information above using Twitter, it went viral. I think I have worked out why. Health authorities have been giving us two messages: once you have the virus there are no drugs that can kill it or help you get rid of it. But also, wash your hands to stop the virus spreading. This seems odd. You can’t, even for a million dollars, get a drug for the coronavirus — but your grandmother’s bar of soap kills the virus.

So why does soap work so well on the Sars-CoV-2, the coronavirus and indeed most viruses? The short story: because the virus is a self-assembled nanoparticle in which the weakest link is the lipid (fatty) bilayer. Soap dissolves the fat membrane and the virus falls apart like a house of cards and dies — or rather, we should say it becomes inactive as viruses aren’t really alive.

I was not aware until this week that good old-fashioned soap is significantly more effective than alcohol-based disinfectants.

★ Friday, 13 March 2020