Hand hygiene has become an integral part of our preventive measure towards reducing our risk to COVID-19. One and a half year into the pandemic, most of us would have been well-versed with hand hygiene using alcohol-based hand rub (ABHR), knowing which types of alcohol we need in a hand sanitisers, the concentration of alcohol effective against coronavirus, and the need to keep our hands clean to stop the transmission of SARS-CoV-2. Amid all this useful information about ABHR, one key information is seemingly missing – how much (volume of) hand sanitiser do I have to use to properly disinfect my hands?
Proper hand disinfection predominantly involved covering (and rubbing) the hands with enough ABHR to ensure that the alcohol eliminates the microbial contaminants on our hands. This exact question on how much to use to achieve a complete hand coverage was recently addressed by Voniatis and colleagues from Hungary (1). Employing volunteers (with varying hand sizes from both genders), the study encompasses blind assessment of volunteers using specific volume of ABHR and then measure the areas untouched or missed by the participants. Note that all participants were given training to hand hygiene theory to minimize data variation due to lack of knowledge/techniques.
The uncovered hand surfaces to the volume used was found to be inversely correlated, meaning more volume resulting in more coverage. For example, participants who uses 1 millilitres (mL; ~half a teaspoon) had 7.1% of their hands uncovered by the ABHR whereas those who use 2 mL and 3mL had only 1.68% and 1.02% of their hands remaining uncovered respectively.
So, what is the ideal volume?
Based on the presented data, 3 mL is seemingly the ideal volume to be used since it can achieve the same percentage of disinfected areas on different (both smaller and larger) hand sizes of volunteers. Although usage beyond 3 mL further reduce the ‘missed’ areas on the hand, the usage of 3 mL or more resulted in an increased spillage during the hand rubbing procedures and the longer drying times becomes a concern, especially for healthcare workers (1).
“3 mL is seemingly the ideal volume…”
In a separate study, 3 mL has also been demonstrated to be the minimal volume required to pass the European standard for hand hygiene, EN1500, on the hands of volunteers (2). EN1500 is a global recognized standard for testing of ABHR to reduce the level of microbes for normal hand hygiene practices.
Reality vs. data
The reality of the volume of ABHR used in practice, especially in this pandemic, is worrying because of the lack of awareness of the need to cover the entire hand surfaces to achieve adequate disinfection. More than often, the act of disinfecting the hands consists of going through ‘the motion’ using insufficient volume rather than a proper hand disinfection with the right product (3), the right amount and correct rubbing techniques (4).
The pictorial representation in Figure 1 (refer to the slideshow above) serves as a demonstration of the ‘usual’ volume used versus the ideal volume of 3 mL by the above-mentioned studies (1,2). The differences in the volume is a good reminder that we need more hand sanitizer when we perform hand hygiene to achieve complete hand coverage, and thus disinfection.
Time to re-think
As COVID19 starts to take a footing again in many countries, it will be prudent for us to dive deeper into how we can further contribute to stop the transmission of the virus. Hand hygiene will remain a critical component and doing it more effectively will further solidify our effort against this impervious pathogen of a century. Therefore, it is time to re-think about how we perform hand hygiene, and if we are just following the motion, or doing it correctly with the right amount of hand sanitizer the next time we rub our hands.
The article is contributed by Dr Thomas Oh, Medical and Scientific Affair Manager of Schulke & Mayr Asia
1. Voniatis, C., Bánsághi, S., Ferencz, A., & Haidegger, T. (2021). A large-scale investigation of alcohol-based handrub (ABHR) volume: hand coverage correlations utilizing an innovative quantitative evaluation system. Antimicrobial resistance and infection control, 10(1), 49.
2. Goroncy-Bermes, P., Koburger, T., & Meyer, B. (2010). Impact of the amount of hand rub applied in hygienic hand disinfection on the reduction of microbial counts on hands. The Journal of hospital infection, 74(3), 212–218.
3. Thomas, Oh. (2021). Recall of hand sanitizer – what other option do we have now?. Schulke & Mayr. https://schulkeasia.com.sg/Article-Details/34/Recall-of-hand-sanitizer
4. WHO Guidelines on Hand Hygiene in Health Care: First Global Patient Safety Challenge Clean Care Is Safer Care. Geneva: World Health Organization. (2009). https://www.ncbi.nlm.nih.gov/books/NBK144013/