The science of why handwashing is our best defence

Thom breaks down the fascinating effectiveness of soap and water

For Your Consideration

For Your Consideration

Wash your hands with soap and water.

It’s an admonition that pretty much everybody who ever had a mom was well familiar with long before COVID-19.

Of course, as with so many things that have been part of our daily lives pretty much all of our lives, we know they work, but rarely think about how they work.

Soaps are fascinating molecules. They comprise a head that is hydrophilic (water-loving) and a tail that is hydrophobic (water-fearing).

Most of what we call dirt, is actually grease or oil (fat). Water will not mix with fat because H2O is a polar compound (has different electrical charges) and fats are non-polar. The general rule of thumb is like dissolves like. That’s why washing hands with water alone doesn’t work very well.

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When combined with water, soap molecules’ hydrophilic ends bind to water molecules (creating lather) while the hydrophobic end binds with the grease allowing it to be washed away.

In these past few weeks, we’ve all become very familiar with the spiky images of the SARS-CoV-2 (the virus that causes the disease COVID-19). Under those ominous microscopic spires is the outer layer of the virus, which is made of lipids (fat).

Evolution is clever. Most viruses and bacteria are covered in this way allowing them to cling to our skin. Since we’re constantly touching things in the world around us and then touching our faces with our hands, they become the perfect delivery system for a host of pathogens.

But it also means viruses and bacteria are susceptible to soap.

It doesn’t just wash them away, though. That hydrophobic tail of the soap molecule fleeing the water actually penetrates the fatty outer shell exposing the virus or bacteria and killing it.

It’s not just the science of soap that is fascinating, though, it’s also the marketing. Soaps are what are known as parity products. If all you want to do is get something clean, one is as good as another.

That’s why companies go to a lot of trouble trying to distinguish their products from one another through marketing. One of those marketing tricks, which is pertinent to the discussion of hand-washing to prevent the spread of pathogens, is the anti-bacterial label.

While an antibacterial soap may actually contain ingredients that kill bacteria, as we’ve seen from the science above, it’s not necessary. Providing you are washing your hands regularly and correctly, regular soap is just as effective against SARS-CoV-2 and all the other nasty little germs we come in contact with every day.

Thanks mom.

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