Breaking Down the 20 Second “Rule”
By now, everyone knows that keeping hands clean is important to reduce germs that may cause illness. While washing hands with soap and water is one of the best ways to achieve this, it has to be done correctly. We’ve all heard leading scientists and health organizations tell us to scrub hands thoroughly with soap and clean water for at least 20 seconds, but have you ever wondered, “Why 20 seconds?”
According to the United State’s Centers for Disease Control and Prevention (CDC),1 while 20 seconds is generally recommended, the time needed to wash your hands thoroughly depends on several factors. Indeed, depending on the type and amount of soil on hands, more than 20 seconds may be needed.
To help understand why soap takes time to work, it’s useful to understand how soaps work.
Soaps contain ingredients called surfactants. When lather is generated from soap, this creates pin-like molecules – called micelles – that have two ends. One is hydrophilic – or “water-loving.” The other end is hydrophobic – or “water-hating” – and loves to interact with oils and fats that are commonly found in dirt and germs. These unique properties allow surfactants to work with water to trap, dissolve and carry away dirt and germs (when hands are rinsed).
Now that you understand how soaps work, it’s important to think about where they need to work.
Your hands have many surfaces and crevices to clean, and the lather needs to cover all of them to trap and lift away dirt and germs. It’s important to scrub all areas of your hands, including the palms, backs of your hands, between fingers, and under fingernails. Don’t ignore items like rings, bandages, or splints on injured fingers. If you are doing it right, 20 seconds should allow enough time to be thorough and allow soap molecules to do their job on all of your hands’ unique surfaces.
Still not convinced that 20 seconds is really needed? Physicists recently published a study using mathematical models to confirm that it does indeed require about 20 seconds of rubbing to dislodge germs from hands.2
Tips for clean hands
While setting a timer or singing the “Happy Birthday” song twice are great ways to make sure you are washing for at least 20 seconds, there are a few other tricks to help your soap work its best to ensure you are removing dirt and germs from all of those hard-to-get-to places:
- Use clean, running water. Germs can be transferred to your hands from dirty or contaminated water. If you do not have clean running water, the CDC recommends using a hand sanitizer containing at least 60% alcohol.1
- Use the right amount of soap. Some dispensers may actually require more than one “pump” to clean all of the hands’ surfaces, especially if they are heavily soiled with oily or greasy materials.If using a bar soap, make sure to vigorously rub the wet bar between the hands long enough to generate enough lather to cover the hands surfaces before scrubbing for 20 seconds.
- Choose a soap with quick lather. Lather creates friction to help lift away dirt and germs. Some soaps, including foams, may generate lather more quickly or easily than others – reaching their peak dirt and germ removal faster.
- Choose a soap that rinses easily. With the dirt and germs “stuck” to the surfactants in the soap, it’s important that they easily come off our hands and are rinsed down the drain.
- Dry hands thoroughly. Wet hands spread germs more easily than dry hands.1 Clean towels can also help to physically remove any remaining dirt and germs. Whether using a clean towel or an air hand dryer, make sure to dry all the same surfaces that were cleaned (including between the fingers).
- Consider hand sanitizer for added confidence. For the highest levels of hand hygiene, use an alcohol-based hand sanitiser after washing to help with spots you may have missed or deep crevices where germs may be lurking, particularly if you are worried about how well hands were washed or what you’ve been in contact with.
Here at NORSAN UK we are the master distributor for GOJO Industries Europe. We stock and supply the extensive range of GOJO/PURELL soaps and skincare products.
If you have a requirement for GOJO/PURELL please contact us with your enquiry.
1. The Centers for Disease Control and Prevention. Frequent questions about hand hygiene. https://www.cdc.gov/handwashing/faqs.html. Accessed January 27, 2022.
2. Hammond P.S. “Will we ever wash our hands of lubrication theory?” Physics of Fluids 33 (8), 2021.
3. Bioscience Laboratories, Inc., Bozeman, MT, Study # 170398-101, Health Care Personnel Handwash, July 5, 2017; Augustine Scientific, Newbury OH, Ex Vivo Soil Removal Analysis, August 5, 2017; Augustine Scientific, Newbury, OH, CRT Surface and Interfacial Rheology Analysis, June 30, 2017