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How does soap kill viruses and bacteria?

We’ve been told over and over again, washing our hands as frequently as possible is the best way to protect our health and safety from Coronavirus – but how important is soap?

In a previous blog, we spoke about the importance of handwashing and how to do it properly. One of the steps is to apply soap. This is because soap completely destroys viruses like Coronavirus (COVID19).

Viruses are essentially sacks of material surrounded by a layer of proteins and fat which are really good at sticking to all types of surfaces – like your hands.

The layer of fat provides the virus with a protective coating against water. Fats and water don’t mix very well on their own, so when you wash your hands with just water, the water runs straight over the top of the fat – straight over the virus.

To demonstrate this, think about how oil and water mix – or more accurately how they don’t mix. Oil is liquid fat and when you add drops of oil to a container of water, they don’t mix. The oil will remain separated from the water and float at the top. The same thing happens when you rinse your hands with water, the water doesn’t mix with the fatty virus skin and so doesn’t clean it off your hands.

A glass of water with oil rising to the top of the cup.

Soap has a super power for fighting against viruses. It is made of modules with two very different ends, one end of the molecule is attracted to water, the other end attracts fat. This means that when soap comes into contact with the fatty layer of the virus, it connects itself and pulls the fat apart – destroying the protective layer and exposing the virus material to the water. The water then washes away the virus material from your hands. 

The reason we are told to wash our hands for about 20 seconds is because the soap takes that long to attach itself to the fat and rip it apart. Any less than that (even that 15 seconds) and the soap won’t have long enough to do its job.

A mother and son washing their hands over the sink in the kitchen.

The best part is, this reaction works with any soap. It doesn’t have to be a soap labelled as anti-bacterial and it doesn’t have to hold any other special property – just regular no-frills soap will do.

If 20 seconds feels like an eternity, just hum or sing a song of that length. Examples could be happy birthday twice, Prince’s Rasberry Baret or Dolly Parton’s Jolene.

Just make sure to wash your hands, be safe and keep singing.

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