Do all soaps work against COVID-19?
While hand-washing removes visible dirt, it’s hard to tell what effect it’s having on the invisible bacteria and viruses. Many soap brands proudly proclaim that, thanks to anti-bacterial additives, they are more effective. This leaves many people thinking - ‘Is my normal soap bar enough to fight COVID-19?’
Let's understand soap molecules
A single drop of soap contains millions of molecules called amphiphiles. If you could see an amphiphile, it would look like a tadpole - with a round head and a long, skinny tail. The head of a amphiphile is polar i.e. it carries a charge and is attracted to water (hydrophilic). The tail, on the other hand, is non-polar and repulsed by water (hydrophobic).
The cleaning action of soap in water
When these amphiphiles (soap molecules) come in contact with water, their tail sticks to particles like dirt - while their head faces out, attracted towards the water. This is how soap and water wash away dirt. When an amphiphile is exposed to the lipid membrane of bacteria or viruses (like the novel coronavirus), the tail burrows into the lipid layer. This breaks apart the lipid membrane - making the bacteria or virus come apart.
So, what kills the virus?
In a nutshell, it’s the soap, and not any special additive in it, that kills the bacteria/virus - and is then washed away by water.
Are anti-bacterial soaps better at killing the novel coronavirus?
No. There's no benefit of using anti-bacterial soap against COVID-19. Anti-bacterial soaps contain an additive called triclosan, that are believed to disrupt bacteria. But since COVID-19 is a virus, that additive does nothing. Health agencies such as the US FDA have also found that anti-bacterial soap are not more effective than normal soap. It’s the soap, and not its anti-bacterial additive, that matters.
So are all soaps effective against COVID-19?
Yes. All types of soap (including handmade soaps) work against bacteria and viruses that have lipid membranes. They disrupt the membrane so the bacteria/virus falls. Since COVID-19 has a lipid membrane, soap will kill it. Don't discriminate when choosing a soap. As long as it’s lathering up, creating bubbles, and acting as a molecular surfactant, it's killing the coronavirus!
Do soaps kill all viruses?
No. Soap may not work on all viruses. Some viruses are protected by protein coats that can't broken apart with soap.
What about the 20 second rule? How important is that?
There is no evidence as to why 20 seconds is the recommended washing time but it's generally accepted that a longer washing period is better. 20 seconds is long enough to wash all parts of your hands, and gives the soap enough time to disrupt the membranes of the virus.