How does soap break the cycle to prevent infection?

People tend to see soap as a feel-good product and focus on its fragrance, texture and soothing properties. But the unique natural hybrid structure of regular soap can destroy and dislodge harmful microorganisms, bacteria and viruses – including coronavirus.

Soap molecules have polar ends, being a hydrophilic head and a hydrophobic tail. Essentially, this means that soap molecules behave in a way similar to magnets: one end attracts water, while the other repels water and attracts fat. (1)

Some pathogens, including the virus molecules that make up coronavirus, are coated in a fatty membrane that protects the essential proteins inside. It’s these proteins that allow viruses to survive and infect human cells. When soap is introduced, its hydrophobic tails pierce that fatty membrane, rupturing the virus molecule, spilling its contents, and rendering it useless.

Speaking to the New York Times earlier this month, Acting Head of Chemistry at the University of New South Wales, Professor Pall Thordarson, likened soap’s hydrophobic tails to “crowbars that destabilise the whole system.”

At the same time, soap molecules lift bacteria off the skin by breaking down the chemical bonds that allow microbes to stick to surfaces. This means that when you rinse your hands after washing, the defunct bacteria molecules are washed away with the soap.

The case for hand sanitiser

Hand sanitisers formulated with a minimum of 60 percent alcohol act in the same way as soap: by destabilising the virus molecule’s fatty membrane to destroy it. But, given that sanitising gel is not rinsed off, it does not physically remove the defunct microorganisms from the skin. For that reason, disinfectants, liquids, gels and creams containing a high percentage of alcohol are very useful, but should be considered a good backup for when soap and water are not available.