Why normal soap kicks hand sanitizer’s butt when it comes to the Corona virus

With the Corona virus COVID-19 spreading and disinfection issues being on everybody’s mind, hand sanitizers have been selling out first. And if you manage to find some in the market, it will be for hilarious prices. Looking at science tells us that this is unnecessary: The best weapon against the virus is normal soap! Here is why:

How viruses spread

The Corona virus spreads via droplet infection – Whenever an infected person coughs or sneezes, the droplets distributed will contain viruses which can affect others. Measurements have shown that a normal sneeze will spread droplets over a distance of 0.6 meters and drops travel at speeds of 4.5 meters per second [1]!

This is why it is important to keep a distance: You never know if the person next to you is infected and when they are going to sneeze. If you keep a meter between you and others, it will lower your risk to breathe in what others sneezed or coughed!

When these droplets reach a surface, they will be able to “survive” on that (or remain active, because we don’t consider viruses to be alive). Even if the drop dried out, the virus can remain active for a while. For the Corona virus it is not conclusively known yet how long it does survive on surfaces [2], but there is much speculation going on out there.

Why soap is the best weapon against the corona virus! COVID-19
Photo by CDC on Unsplash

How long depends also on the kind of surface: On rough surfaces it is much easier to stick for the virus, while it can’t attach that well to flat surfaces. Molecular interactions also play an important role: Viruses won’t interact much with steel, porcelain or teflon and therefore are detached much easier [3]. To skin however, viruses attach strongly [3] – and this is why they spread so well among humans.

The composition of our skin makes a very favorable environment for viruses to stick to due to its molecular composition. So whenever we touch e.g. a steel surface with a virus on it with our hand, it will easily detach from the unfavorable metal surface and stick to our skin. Once we now touch our face, it can reach our airways and mucous membranes – which will lead to infection if your immune system can’t cope with it.

Whenever you touch a contaminated surface, the virus is likely to stick to your skin. Therefore is is important to clean your hands regularly and avoid touching your face! Try to avoid places with a high people throughput such as public transport and try not to touch anything unnecessarily.

How washing hands can save us from infection

If it is only on our hands, we still have a good chance to get that virus off before it can infect us. Normal water can help to detach the virus, but soap is much more effective: Just like normal dirt, virus can be removed better with soap due to its molecular structure. Soap molecules are able to enclose dirt (and with it, also the virus) and make it soluble in water. Only then can it me removed easily with some water.

How soap removes dirt and the corona virus from skin
How soap removes dirt and viruses: Soap molecules have a side soluble in fat, which sticks to contaminants such as dirt, and a water-soluble side shown here with blue balls. By covering the dirt (in which the virus sticks to our skin) with the water soluable shell, the dirt and virus organisms can easily be removed with water.

Furthermore, soap not only helps to remove the virus, it is also able to make it inactive: The so-called surfactant molecules in soap are able to break apart the outer shell of the virus because these are not as strongly bound [3]. Therefore, soap not only removed the virus from our skin, it also eliminates the thread!

Wash your hands regularly with soap and water – but make sure to scrub for some time so that you get it all off! Contaminated dirt can remain in wrinkles and grooves of your skin. It takes some scrubbing and soaking to make sure everything is gone.

Why hand sanitizer is no match for soap

Disinfecting your hands with disinfectants is not as effective as washing your hands: To match with washing your hands in soap, the disinfectant needs to make all virus organisms inactive instantly on your hands. Since you are not able to wash of anything with the disinfectant, you rely on its effect to inactivate the virus.

Commercially available disinfectants are usually alcohol based and are able to dissolve the outer membrane of the virus – making it inactive – but only in a high enough concentration [3]. Normal alcohol (e.g. vodka) contains only 40 % of ethanol which is not enough. Therefore many disinfectants also have some soap in it to increase its effectiveness. Antibacterial substances won’t help as they don’t work on viruses.

Because of its double effectiveness by removing and eliminating the virus, washing hands in soap is therefore more advisable than using disinfectants. If you don’t have the chance, hand sanitizers are a good backup.

Public hand sanitizers often are less sanitary e.g. if you need to open a bottle to use it. This might actually increase your chance of infection!

The good thing about this: We don’t have to buy disinfectant for those ridiculous prices right now, normal soap is much more inexpensive and works even better!

The 6 basic life hacks to limit the spread of the virus

While there is no reason to panic, this is a good time to adjust our behavior to help limit the spreading of this virus:

  • Avoid crowds and gatherings. Whenever you can, it is advisable to keep a meter distance to others to limit your chance of infection! Home office is advisable whenever possible. Try to avoid all unnecessary trips outside.
  • Try not to touch things in public spaces if unnecessary.
  • If possible, avoid public transport – this might be a great time to go by bike!
  • Avoid touching your face as much as possible.
  • Wash your hands regularly and intensely with soap.
  • If you are unable to wash your hands, use hand sanitizer. Whenever possible, choose soap over disinfectant!

By the way, of course I am not a virologist. But I am a surface scientist. My advise here is based on scientific facts I know from my education or articles I found by renowned scientists. Please don’t listen to “facts” from unknown sources on social media, there is a lot of fake news out there!

How is the virus affecting you? Are you in quarantine or working from home? Do you have other tips to share? Let us know in the comment section and please – stay safe!

[1] https://www.ncbi.nlm.nih.gov/pubmed/23560060
[2] https://www.health.harvard.edu/diseases-and-conditions/coronavirus-resource-center#Prevention
[3] https://www.marketwatch.com/story/deadly-viruses-are-no-match-for-plain-old-soap-heres-the-science-behind-it-2020-03-08

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