28th May 2020

Ask The Expert: Science Of Sanitisers (SOS)

Andrew Howell, MD of BCB International Ltd, says We now know that hand sanitisers are one of the vital defences in our armoury in the fight against Coronavirus; part of the new “norm” for the future. However, even among professionals, there is much confusion over what hand sanitiser to use. Not all are equal to the job in hand.

Many authorities defer and refer to the World Health Organisation (WHO) as the authority to follow. WHO published guidelines in April 2010 on two suggested hand sanitiser formulae using alcohol as its active ingredient. Other formulas available in Britain use polymeric biocides, which have not been as extensively tested or Quaternary Ammonium Compounds, which show poor mycobactericidal activities and are certainly not as effective as alcohol.  Alcohol attacks and destroys the envelope protein that surrounds some viruses, including coronaviruses.

However, most of the test information for alcohol-based hand sanitiser is based on pre-COVID19 test data. This pits the hand sanitisers efficacy against bacteria, not against viruses. This is surely missing the point. The threat is Coronavirus, not bacteria. Very few hand sanitisers available appear to be tested against viruses and specifically Coronavirus.

Viruses, including Coronavirus, are notoriously more difficult to kill than bacteria. Empirical evidence** has shown that Coronavirus is roughly 10 times more resilient compared to some bacteria, like E. Coli., when tested against alcohol hand sanitisers.

Test standards like EN1500 and EN 1499 (which relates to handwashes, not hand rubs) are a good benchmark against bacteria but are not testing the viricidal efficacy; unlike the EN14476:2013 + A2:2019 tests.

In my opinion the WHO formulae are inappropriate for the current epidemic. Written over 10 years ago and was aimed at low volume production in the developing countries. As such, it includes Hydrogen Peroxide (H2O2) which the WHO state is not for efficacy, but is included to help clean dirty containers and mixing vessels you may typically expect to find in developing countries.

The WHO formula does not contain a de-tasting agent and is a thin liquid. We believe a viscous gel rather than a liquid is more effective as the contact time, (the time between the product and any virus or bacteria) is the second most important factor to defeat any micro-organisms. Liquid evaporates quicker and can run off your hands compared to a thicker viscous gel.

Concentration of alcohol is though all important. Alcohol of say 95% or 100% is ineffective; it needs water to work. Some hand sanitisers do not even quote what percentage of alcohol is in their formula. Experts agree 60 % alcohol should be a minimum. But why? A hand sanitiser of 70 % concentration claims a 99.9% effectiveness against bacteria. As viruses are approx. 10 times more difficult to kill than bacteria then this 70 % concentration would only be 99% effective against viruses. If even after washing your hands you will still be holding millions of viruses in your hands.

If we assume clean hands are typically contaminated with ten million virus cells (Log 107)  before treatment, the below table shows the possible comparison of viruses which maybe left immediately after washing with soap, sanitising with a 70% sanitiser or sanitising with Dr. Browns 80 % sanitiser.

Product examples Kill Rate Log 107Reduction Viruses remaining
No treatment 0% 0 10,000,000
Hand washing 90% 1 1,000,000
70% hand santiser 99% 2 100,000
Dr. Brown’s 80% hand sanitiser 99.99% 4 1,000

BCB have devised a thick, high strength, 80 % alcohol formula, called Dr Brown’s. British quality, it is tested and proven to kill more than 99.99% of Coronavirus, as evidenced by BS EN 14476:2013 + A2:2019 testing. It is therefore possibly that Dr Brown`s 80 % thick formulae could be 100 times more efficacious than 70 % formulae. With the extremely virulent nature of Coronavirus, being 100 times more effective, will make a significant difference to its defeat and your health.

This test should be the standard we should all look for in our hand sanitisers. That said, Dr Brown’s has also been tested and approved to EN 1500 and EN 1276. Hence the empirical evidence quoted above ** where Dr Brown`s 80 % formulae showed at least a 5 Log 10  reduction (99.999%) for bacteria (EN 1500), compared to more than a 4 Log 10 reduction (99.99%) for Coronavirus (EN 14476:2013 + A2:2013).

Finally, the quantity of hand sanitiser used should be sufficient to cover the palms and back of your hands and between your fingers. Approx. half a teaspoon full or 3 millilitres should be sufficient.

Test, innovate and adapt. Speed of innovation is vital to keep ahead of this insidious virus, as the possibility of it mutating due to it’s wide exposure is a great risk. It is believed there are already two strains of COVID -19 in China.

Darwin was correct when he said…

“It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.”