How much alcohol gel should I use?
This is a great question and one we get asked all the time.
As we all know dirty or contaminated hands can transmit micro-organisms that may cause infection, and that cleaning our hands reduces this risk. Good hand hygiene is important for public health – it is a simple but effective tool in controlling infection.
Soap and water handwashing or alcohol based disinfectants? They are both effective
Good hand hygiene can be achieved either through traditional soap and water hand-washing or alcohol based hand disinfectants. Which method is most appropriate depends on availability and on whether hands are visibly soiled.
Remember that alcohol gel is less effective and should not be used when hands are visibly soiled or greasy – for example after gardening or doing some DIY on a motorbike. Alcohol gel can kill the vast majority of bacteria and viruses but will not remove dirt and organic material. Hand sanitizers also may not remove harmful chemicals, such as pesticides and heavy metals like lead. In this situation washing with soap and water is more effective.
When hands are not visibly soiled alcohol gel may have an edge over soap and water as it can be more effective in killing certain types of microorganisms. It also does not dry or irritate skin like frequent washing with soap and water does.
So how much alcohol gel should we use?
The short answer is that there are no international or national standards on quantity. Rather, what is important is that the surfaces of hands are fully covered with a suitable alcohol hand sanitiser.
It follows that quantity is dependent on hand size – larger hands have a larger surface area than smaller hands and need more alcohol gel to fully cover them. Directions that call for a “small amount” or a “coin sized amount” are not very clear; you should use an amount that fully covers all the surfaces of your hands.
A relevant study published in the American Journal of Infection Control used 1ml, 2ml and 3ml of hand sanitiser containing an unltraviolet (UV) tracer on a team of volunteers. They then shone UV light on the volunteers’ hands to estimate the amount of hand surface covered by each amount of hand sanitiser (Walter Zingg, Tamas Haidegger, Didier Pittet. “Hand coverage by alcohol-based handrub varies: Volume and hand size matter.” Am J Infect Control 44 (12): 1689-1691. Published: 1-Dec-2016. DOI: 10.1016/j.ajic.2016.07.006).
The team found that 1ml was generally not sufficient for effective hand hygiene as it it did not fully cover even small hands. The study found that 2–3ml was a more appropriate amount, and that the largest size hands needed more than 3ml to cover all surfaces.
2-3ml is about half a teaspoon so keep this in mind when using hand sanitisers. And to be effective, alcohol gel needs to be in contact with hands for at least 15 seconds, so take your time and rub your hands thoroughly.
Safe use of alcohol-based hand sanitisers
To protect yourself and others against COVID-19 and other infectious diseases, clean your hands frequently and thoroughly. Use alcohol-based hand sanitiser that contains at least 60% alcohol or wash your hands with soap and water. If you use an alcohol-based hand sanitiser, make sure you use and store it carefully.
- Keep alcohol-based hand sanitisers out of children’s reach. Teach them how to apply the sanitiser and monitor its use.
- Apply 2-3ml on your hands. Use an amount that fully covers all surfaces of your hands and rub your hands for at least 15 seconds.
- Use hand sanitiser after you have been in a public place and touched a surface that may be frequently touched by other people, such as door handles, tables, petrol pumps, supermarket trolleys, cashpoint screens, etc.
- Avoid touching your eyes, mouth and nose immediately after using an alcohol-based hand sanitiser, as it can cause irritation.
- Hand sanitisers recommended to protect against COVID-19 are alcohol-based and therefore can be flammable. Do not use before handling fire or cooking.
- Do not rinse or wipe off the hand sanitiser before it’s dry; it may not work well against germs.