Hand Sanitizer or Soap: making an informed choice for COVID-19

When applied to hands thoroughly and scrubbing for at least 20 seconds, both soap and alcohol-based hand sanitizers will stop the corona virus.

Corona-viruses get their name from the ‘corona’ surrounding the virus—specifically, the protein spikes embedded in its surface. The spikes, which are responsible for infecting the host, are anchored into a membrane. The membrane is the ‘shell’ of the virus. This is the coronavirus’ weak point.

Any soap will protect you. Standing in the soap aisle, it’s easy to get overwhelmed by choice. But when it comes down to the chemistry, soaps will all work against the novel coronavirus.

Soap molecules have two chemically distinct parts: a hydrophilic (water-loving) ‘head’ and a hydrophobic (water-hating) ‘tail’. The head helps the soap mix with water, while the tail can interact with other hydrophobic molecules like lipids.

Lipids are a class of biological molecules that includes oils and fats. Luckily for us, the coronavirus’s membrane is mostly made up of lipid molecules. They are held together by weak chemical interactions between individual molecules.

Scientists think that the soap’s tail can disrupt the weak interactions between lipid molecules in the membrane, tearing it apart. If the virus is broken up before it has safely sheltered in a host cell, it will no longer be able to do its infectious job—like a machine with its parts falling out.

Soap molecules then surround virus fragments with all tails facing inside. This cluster is called a micelle. The outward-facing hydrophilic heads allow the micelle to be washed down the drain with water.

The same lipid molecules that enclose the virus in a membrane also cause it to cling to the oils on your skin. Using soap to wash your hands weakens these interactions, and virus particles are washed down the drain. Water alone won’t do.

This action of ridding your hands of virus particles is just as important as any role soap plays in interfering with the virus’s membrane.

If you have no soap on hand, the World Health Organization and the Australian Government Department of Health both recommend alcohol-based hand sanitisers to remove the novel coronavirus. Your hand sanitiser might contain ethanol, isopropanol, n-propanol or a combination of these three alcohols. All are effective against lipid-wrapped viruses like the novel coronavirus.

Alcohol-based hand sanitisers are thought to work by preventing the proteins of microbes—including bacteria and some viruses—from functioning normally. Hand sanitisers with a high alcohol content might also interfere with the lipid shell surrounding the coronavirus.

To be effective, hand sanitisers must contain at least 60 per cent alcohol. Some researchers recommend more than 75 per cent alcohol.

A higher alcohol content is not automatically more effective, either. The water in the sanitiser can keep the alcohol from evaporating too fast, allowing the virus to be drenched for longer. Water is also needed for the process that interferes with protein function.

Make sure to check the expiry date too, because the alcohol can evaporate even out of sealed containers.

The tiny coronavirus is a master at hiding out in pores, including on your skin and surfaces like wood. Whether you’re using soap or hand sanitiser, it’s important to lather up your hands for at least 20 seconds and cover every nook and cranny.

Source: https://www.science.org.au/curious/people-medicine/hand-sanitiser-or-soap-making-informed-choice-covid-19