As the coronavirus pandemic spreads around the world, sales of hand sanitiser have skyrocketed, leaving shelves empty; so much so that luxury goods conglomerate LVMH (Moët Hennessy – Louis Vuitton SE), announced on Sunday 15 March that it had instructed its LVMH Perfumes & Cosmetics business to “use all of the production facilities of its perfumes and cosmetics brands (Parfums Christian Dior, Guerlain and Parfums Givenchy), based in France, to produce large quantities of hydroalcoholic gel from Monday”.

Along with social distancing, soap and hand sanitiser have come out as the most effective tools we have right now to battle the spread of the virus, and it’s all because of how soap breaks things down at a molecular level.

To understand why it works so well one has to understand a bit about the exterior structure of the virus.

For its protection as well as to help it spread, the virus has a membrane of oily lipid molecules. Soap effectively breaks apart the virus’s shell. Then essential proteins will spill into the water from the virus, making it ineffective.

A simpler way to look at it is to think of what happens when you mix oil and water. The two liquids will typically separate, but once you add soap into the mix, the oil will break down into smaller amounts.

The soap’s molecules also affect the chemical bonds that cause viruses to stick to surfaces, making them easier to wash off the skin. So by the time you rinse your hands, all the microorganisms that have been rendered ineffective by the soap will be washed off.

Pall Thordarson, a professor of chemistry at the University of New South Wales, Sydney, in a series of tweets as well follow-up articles he wrote, noted the following: “Wood, fabric and skin interact fairly strongly with viruses. Contrast this with steel, porcelain and at least some plastics, such as Teflon. The surface structure also matters. The flatter the surface, the less the virus will “stick” to the surface… The skin is an ideal surface for a virus. It is organic, of course, and the proteins and fatty acids in the dead cells on the surface interact with the virus through both hydrogen bonds and the ‘fat-like’ hydrophilic interactions.”

Thordarson added: “Washing the virus off with water alone might work. But water is not good at competing with the strong, glue-like interactions between the skin and the virus. Water isn’t enough… The soap not only loosens the “glue” between the virus and the skin but also the Velcro-like interactions that hold the proteins, lipids and RNA in the virus together.”

Hand sanitisers with at least 60% alcohol have a similar effect on the virus, as the alcohol will also break the outer membrane of the virus. However, according to Thordarson, they are not as effective as soap, and the anti-bacterial agents in many hand sanitisers do not affect the virus’ structure at all, apart from the soap and alcohol. That is not to say hand sanitiser doesn’t work, it does, but good old regular soap works even better, partly due to the handwashing process, which involves rinsing.

So, where possible, make sure to use soap, and when you can’t, make sure to reach for the hand sanitiser. As for some brands that market soap with added antibacterial agents, promising more effective cleaning, according to research cited by the Centre for Disease Control, “To date, studies have shown that there is no added health benefit for consumers (this does not include professionals in the healthcare setting) using soaps containing antibacterial ingredients compared with using plain soap.”

(Please do not let the water run while you’re soaping your hands – Ed).

When it comes to the optimal length of time for handwashing, the 20 seconds rule isn’t a new one. It has long been a recommendation for general good hygiene. According to the CDC recommendations published prior to the coronavirus outbreak, “Evidence suggests that washing hands for about 15-30 seconds removes more germs from hands than washing for shorter periods.” 

The important thing to remember is to make sure that the entire surface of the hands is scrubbed clean as the virus can get into the tiny folds on one’s hand; the longer one washes, the more likely they are to cover all surfaces. The soap also needs time to interact with the virus, which the 20-second recommendation allows for. ML

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