Efficacy of sanitizers against SARS-CoV-2 based on alcohol content

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SUMMARY

The efficacy of hand sanitizers against SARS-CoV-2 is significantly influenced by their alcohol content, with WHO recommending formulations of 80% (v/v) ethanol and 75% (v/v) isopropanol (IPA). Many commercially available sanitizers contain lower concentrations, such as 70% ethanol and 72.43% denatured alcohol, raising questions about their effectiveness. Research indicates that even 60% (v/v) alcohol can be effective, but the credibility of such claims varies. The term "denatured alcohol" typically refers to ethanol mixed with additives to prevent ingestion, and its safety in sanitizers is contingent on the specific chemicals used.

PREREQUISITES
  • Understanding of WHO guidelines for hand sanitizers
  • Knowledge of alcohol concentrations and their effects on microbial efficacy
  • Familiarity with the concept of denatured alcohol and its uses
  • Basic chemistry knowledge regarding ethanol and isopropanol
NEXT STEPS
  • Research the WHO guidelines on hand sanitizer formulations
  • Investigate the effectiveness of various alcohol concentrations against SARS-CoV-2
  • Explore the safety and composition of denatured alcohol in sanitizers
  • Examine EN 1500 standards for hygienic hand antisepsis
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Healthcare professionals, sanitization product manufacturers, and consumers interested in understanding the effectiveness and safety of hand sanitizers against SARS-CoV-2.

Wrichik Basu
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Ethanol and 2-propanol (hereafter abbreviated "IPA") are the two alcohols that are used in hand-sanitizers. As per the standards set by WHO, the recommended levels are 80% (v/v) of ethanol and 75% (v/v) for IPA, along with other components like glycerol and hydrogen peroxide. Refer to the https://www.who.int/gpsc/5may/Guide_to_Local_Production.pdf for details (a pdf file). A snapshot:

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None of the handrubs I have seen has the above composition. The ones that are preferred by hospitals have 70% (v/v) ethanol and 2.5% (v/v) chlorhexidine gluconate IP; these are not generally available in pharmacies for the common people.

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Sanitizers produced by another famed brand has 72.43% (v/v) alcohol IP (denatured). My knowledge in chemistry is quite limited, but I thought denatured alcohol is poisonous; no idea how they are putting it in a sanitizer.

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Question: Are these sanitizers with a lower percentage of alcohol effective against the SARS-CoV-2?

One website says that even 60% (v/v) of either of the two alcohols will work, but it did not site any sources and hence lacks credibility.
 
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Wrichik Basu said:
Sanitizers produced by another famed brand has 72.43% (v/v) alcohol IP (denatured). My knowledge in chemistry is quite limited, but I thought denatured alcohol is poisonous; no idea how they are putting it in a sanitizer.
"Denatured alcohol" does not -as far as I know- have a "chemical" definition. Typically, it just means ethanol (the stuff you can drink) which has had some other chemicals added to it to discourage people from drinking it. What is is added depends on where you are in the world, but typically it will be something like methanol (which is indeed somewhat toxic if you get it on your skin) plus perhaps some other chemicals to induce vomiting and a dye.
In this context I doubt they use methanol, denatured here probably just means that somewhere in the production line something has been added to make the hand sanitiser harder to drink (which btw is something people do)
 
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From the same WHO guidelines (a little further down):
The microbicidal activity of the two WHO-recommended formulations was tested by WHO reference laboratories according to EN standards (EN 1500). Their activity was found to be equivalent to the reference substance (isopropanol 60% v/v) for hygienic hand antisepsis.
70% ethanol is standard in most bio labs I’m familiar with.
 
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