Should we be promoting handwashing at different times during infectious disease outbreaks?
Normally at a community-level, we focus on the following critical handwashing occasions:
Before food preparation
Before eating food or feeding a child food
After using the toilet
After cleaning a child’s bottom.
Handwashing at these critical occasions should continue to be promoted during infectious disease outbreaks. However, depending on the transmission route of your focal disease, you may wish to encourage handwashing at additional times. For instance, if you want to interrupt the transmission of COVID-19, you should also encourage handwashing at the following times:
After coughing or sneezing
When entering or leaving the household or any other building
After coming into physical contact with anyone outside your household
After touching surfaces when outside the home (e.g. door knobs, railing, money etc.)
After visiting a public space, including public transportation, markets and places of worship
Before, during and after caring for a sick person
There may also be additional times that are relevant in your context. If it is not possible to wash hands immediately after contacting any of the above (e.g. whilst in a public place), care should be taken to avoid touching the face. Hands should be washed immediately after returning home.
Source: Global Handwashing Partnership
How long should hands be washed for?
Studies show that within one hour, hands typically become as contaminated as they were prior to washing them. Therefore, it is important that we encourage populations to wash their hands frequently, though the recommended frequency may vary depending on the disease of interest’s transmission route. For instance, when considering COVID-19, we know that SARS-CoV-2 can transmit via surfaces, as well as respiratory droplets. Therefore it is important that hands are washed at additional and different times to what would normally be recommended for the control of diarrhoeal diseases. Information about when hands should be washed is available here.
Recommendations about handwashing duration will vary depending on whether guidance is aimed at the general public or health care workers. Unsurprisingly, it is particularly important that health care workers and patients or visitors to health facilities wash their hands more thoroughly and frequently than the general population.
However, there are also different recommendations about how long hands should be washed for within domestic or workplace settings. For instance, the WHO recommends that the handwashing process (from wetting hands to hand drying) should take between 40-60 seconds. They also suggest that hand cleaning with alcohol-based hand rub should take 20-30 seconds. Meanwhile, the Centres for Disease Control and Prevention (CDC), recommends hands should be washed for at least 20 seconds.
In reality we know that most people wash their hands for less than 10 seconds. These findings come from studies conducted in high income settings where soap and piped water are readily available (study 1, study 2, study 3), so in water scarce areas or low and middle income countries it may be much less.
Studies on pathogens indicate that hands will become cleaner the longer they are washed, however, the process will reach a point of diminishing returns (where lots of effort is required for fairly minimal additional pathogen removal). The table below shows typical reductions of common pathogens according to different durations of handwashing. Evidence suggests that washing hands for 15-30 seconds is effective at removing germs; hence, most global and national guidelines state that hands should be washed for 20 seconds, with an additional 20-30 seconds for drying.
Source: Bloomfield, et al (2007)
Overall, it's important to promote handwashing frequently to reduce the transmission of pathogens. Recommending long durations of soap lathering may make it a less feasible behaviour in areas with water or soap scarcity, so the recommendation is to target a duration that is feasible given your context. This, in addition to frequent handwashing, will contribute to preventing the spread of infectious diseases. When communicating about thoroughly washing hands, try to avoid making it overly complex as people may struggle to digest and apply this information, as demonstrated in this study in Bangladesh.
Below is a guide from the WHO on handwashing in health care facilities. Although it is aimed towards health care workers, it demonstrates different handwashing techniques used to ensure the entire hand surface is covered during handwashing.
Are some types of soap more effective than others?
Antibacterial soap is not more effective in community-settings and under normal use conditions (i.e. when hands are not washed for as long and thoroughly as in laboratory experiments). This is thought to be because of the way soap works at a microbiological level (see our resource on how handwashing with soap works’) and because it takes a while for the antimicrobial properties to be activated and by this time, most pathogens have already been removed from hands. Antimicrobial soap is recommended in health care facilities since it is important to ensure that sinks and drains don’t become reservoirs for pathogens in these settings.
Using nicer soap may make handwashing more desirable and therefore contribute to the development of good habits. In particular, liquid soap is considered more desirable in many settings.
Source: London School of Hygiene and Tropical Medicine
Is alcohol-based hand rub better than soap?
Handwashing with soap is the most commonly recommended method for removing pathogens from hands. This is because soap is effective in removing and killing pathogens and because soap is cheap and affordable. It is also gentle on hands, so repeated use should not cause irritation. Alcohol-based hand rub is effective against many bacteria and viruses, including SARS-CoV-2, but is less widely available and is often more expensive. It is recommended that alcohol-based hand rub be a back-up solution, for when handwashing with soap is difficult or impractical (such as when a person is outside their home).
Alcohol-based hand rub must contain at least 60% alcohol in order to be effective (check the back of the bottle for information). Modern alcohol-based hand rubs rarely cause skin irritation because they normally contain skin softeners to prevent skin drying. For this reason, it is not recommended to promote home recipes for alcohol-based hand rub. For more about perceived risks associated with hand sanitisers, read this article from the WHO.
Should we be promoting handwashing with chlorinated water?
It is not necessary to use chlorinated water for handwashing during most infectious disease outbreaks, as soap and water is highly effective at killing and removing pathogens from hands. Using chlorinated water does kill viruses, but may also cause skin or eye irritations, so within the recent COVID-19 pandemic, the WHO recommend using soap and water or alcohol-based hand sanitiser as both are gentler on skin. However, if the latter is not available or feasible, chlorinated water can be used as a temporary measure.
In some settings, such as those recently affected by Ebola outbreaks, there may be a precedent for handwashing with chlorine to combat the spread of disease. In these settings, it might be more acceptable to promote the use of chlorinated water at public handwashing facilities (but only if it proves challenging to promote handwashing with soap). Chlorinated water may also be considered in locations where soap supplies are limited. Chlorinated water should not be promoted as an option for handwashing at home. Chlorine can be a dangerous chemical and so it is important that it is stored and handled with care.
If preparing chlorinated water for handwashing then a 0.05% solution should be used. Follow the instructions from the CDC as shown below.
Summary of recommendations:
· Handwashing with chlorinated water (0.05%) is effective against many pathogens, including SARS-CoV-2, but is not necessary.
· Handwashing with soap or alcohol-based hand gel should be encouraged.
Can bar soap spread pathogens?
At the start of the recent COVID-19 pandemic, there was a lot of concern around surfaces being contaminated by the virus, so it was reasonable to be concerned about whether bar soap could also be a source of potential infection. It is true that bacteria and viruses can transfer onto bar soap during handwashing. Some studies have found that most bars of soap have an average of 2-5 microorganisms on them at any one time. Interestingly, when these contaminated bar soaps are used, studies have shown that hands have no traces of these pathogens afterwards and that hands are equally as clean as compared to using a brand new bar soap. Studies like this indicate that there is no infection risk posed by sharing bar soap. The reason for this is likely to be because of the way that soap works at a microscopic level (see this resource on how soap works).
How can handwashing be promoted when soap is scarce?
It is rare that people have no soap at all, rather the soap that they do have is prioritized for other tasks, such as bathing, laundry or dishwashing. If this is the case, try implementing activities that remind people of the power of soap. Also remind people in your area that any type of soap can be used for handwashing (see ‘Are some types of soap more effective than others?’) including cheap soap that is often used for laundry. You can also suggest that people create soapy water (see ‘Can soapy water be used?). If you are working in an area where soap is unaffordable for people or is unavailable, using ash may be better than handwashing alone (see ‘Can ash be used for handwashing?’).
Photo of a public handwashing facility in Tanzania where they have created a laundry powder dispenser from a bottle. Source: Twitter
Can soapy water be used for handwashing?
Soapy water has been shown to effectively remove pathogens from hands and be an acceptable and affordable alternative to bar or liquid soap. It can be used in households where soap is limited and can be a particularly practical solution for promoting soap use at public handwashing facilities. This is because people will often feel uncomfortable sharing bar soap in public locations, so liquid or soapy water is more acceptable. However, if using soapy water in these settings, someone may need to be appointed to refill the soap water regularly.
Soapy water can be created by diluting powdered laundry soap or liquid soap. However, be careful not to dilute any soap too much as this will make it less effective. If you choose to dilute soap, make sure that it is still soapy enough that it is able to create a good lather within seconds as this is important in order to effectively remove soap from hands (see this resource on how hand washing with soap works).
Here is a pictorial example of how to create soapy water from laundry detergent powder and how to create dispensers.
What soap alternatives are there and do they work?
In some settings where soap is scarce, inconsistently available, or not prioritized for hand hygiene, it can make regular handwashing challenging to practice. In these environments, practitioners are often curious about the viability of soap alternatives.
There is a global research gap on the efficacy of soap alternatives against enveloped viruses. A 2020 literature review found that there was minimal evidence to suggest that soap alternatives are likely to effectively remove or inactivate SARS-CoV-2, the virus that causes COVID-19.
Given the lack of evidence around most of these soap alternatives, most should not be promoted during COVID-19 outbreaks or in general, to reduce the transmission of other respiratory or diarrhoeal diseases. Many of these soap alternatives have adverse effects which need to be investigated further to understand their impact.
Below we summarise the evidence on alternative handwashing products that can be promoted during COVID-19 outbreaks:
Ash - Ash is the most commonly used alternative to soap and whilst there has historically been poor evidence on the effectiveness of ash against SARS-CoV-2, an unpublished study conducted in late 2022 presents promising new evidence. The study aimed to ‘quantify the reduction in viruses from handwashing with ash or sand compared to handwashing with soap and water for 20 seconds’ and found that, in laboratory conditions, ash and sand with water are as effective at eliminating a surrogate of SARS-CoV-2. Ash is likely to work because it is abrasive, and it creates an alkaline solution which may inactivate viruses. The WHO and UNICEF recommend that ash should be used as a last resort in situations where soap is not available. For more on the use of ash, see this resource.
Chlorinated water - Using chlorinated water does kill viruses, but may also cause skin or eye irritations. Currently the WHO recommends the use of chlorine solutions only in interim emergency settings, until soap and water or alcohol-based hand rubs are available. Chlorinated water should be used in health care settings if soap or alcohol-based hand rub are limited. Chlorine in its solid form or at high concentrations should be stored and handled with care. If preparing chlorinated water for handwashing then a 0.05% solution should be used. For more on this see this resource.
Below we summarise the evidence on methods on alternative handwashing products that should not be promoted during the COVID-19 pandemic because there is little to no evidence on their effectiveness:
Sand or soil: There is mixed evidence about the efficacy of sand, soil or mud for hand cleaning. The use of sand, soil or mud is thought to remove larger microbes from hands through mechanical friction. One study in Bangladesh found that the use of mud for hand cleaning was more efficacious than handwashing with water alone. Moreover, the unpublished study highlighted under the previous section on ash, found that under laboratory conditions, sand is as effective as handwashing with soap for 20 seconds. However, there are risks to using these alternatives. For example, soil may contain other contaminants, pathogens or parasites (such as soil-transmitted helminths that cause intestinal worm infections) which may then be transferred to hands and ingested. The use of soil or mud can be abrasive to the skin and may not be comfortable or desirable to use.
Seawater: Some studies have suggested that in theory, seawater can detach contaminants from surfaces and hands through the dissolving or drying fats and oils. However, there have been no studies on the efficacy of only using seawater to clean hands. It is challenging to use seawater with standard soap as the salt typically prevents soap from lathering. As with sand and soil, seawater itself is often contaminated with pathogenic and non-pathogenic microorganisms from various sources including agricultural chemicals, human and animal faeces. Seawater is also likely to leave a residue on hands, leaving them feeling unclean.
Saline water: Saline water is not widely available outside hospital or laboratory settings and should be prioritised for use in these settings. We do have evidence that saline solution can be equally or more effective than soap for cleaning wounds and preventing reinfection. However, there are no studies that document the efficacy of saline water for pathogen removal from hands or against SARS-CoV-2.
Vinegar: There are no studies on the use of vinegar for hand cleaning. Vinegar has been used as a household cleaning agent for centuries, however it is regarded as less effective than most commercial cleaning products and is not considered to be a disinfectant against viruses. It is unlikely to be efficacious at removing pathogens from hands (including SARS-CoV-2). Since vinegar is acidic, it can also cause skin irritation.
Lemon juice - In some countries, there have been news headlines about using lemon juice as an alternative to soap. There is limited evidence to support the use of lemon juice for handwashing, however, some studies have shown that it may be effective in killing some pathogens. It is unlikely that lemon juice will be efficacious against SARS-CoV-2, because the pathogen has been found to be stable at acidity levels (pH levels) of 3-10. Since the pH of lemon juice is between 2-3, it is unlikely to be acidic enough to destroy the outer membrane of the virus.
The WHO recommends that the following products be used when promoting hand hygiene and lists these in order of effectiveness: water and soap or alcohol-based hand rub, ash where no soap is available and handwashing with water alone as a last resort. Handwashing with chlorinated water may also be an appropriate and effective alternative in some settings. If you are working in a low resource setting, please see this article on how handwashing can be promoted when soap is scarce.
Source: WHO Philippines
Can ash be used for handwashing?
In low and middle income settings, ash is often promoted as an alternative to handwashing with soap. UNICEF and WHO guidelines recommend that ash can be used for hand cleaning when soap is not available. This should be considered as a secondary option as, whilst one unpublished study does suggest comparable efficacy of ash/sand at eliminating SARS-CoV-2 in laboratory conditions, there is a greater evidence base reporting that soap and water are particularly effective at killing and removing SARS-CoV-2.
If recommending ash to households, make sure that they are using the white ash from the centre of a fire once cooled. This white ash is likely to be the most sterile as it was heated at the highest temperature. It is possible that chemicals in the ash could damage the skin, depending on what materials were burned in the fire.
Be aware that handwashing with ash does not feel very nice and does not leave hands feeling and smelling nice in the way that soap does, as such, promoting ash may actually discourage people from practicing handwashing. Conversely, handwashing with ash might be the norm in some settings and might be preferred to handwashing with soap. Nonetheless, we recommend also reminding people that soap of any type can be used for handwashing. See our section on ‘Are some types of soap more effective than others?’ for more information.
Summary of recommendations:
There is limited evidence on the effectiveness of ash for removing or killing SARS-CoV-2, with the exception of one recent study.
Evidence on the effectiveness of ash in general is poor.
In settings where soap is really scarce, remind people that any type of soap is effective for handwashing.
Where there are no other options, handwashing with ash should be encouraged as it is likely to be more effective than handwashing with water alone.
How can we promote handwashing in areas with water scarcity?
When water is scarce, people typically prioritise water for tasks other than handwashing – things like drinking, bathing, laundry, and dishes. In such settings, people may just rinse their hands with water rather than using soap because using soap is perceived to increase the amount of water required. A key behavioural task in areas that are water-scarce will be to reposition handwashing with soap as more important than other household tasks at this time.
There is the potential for handwashing to consume lots of water but hands can be washed with a relatively small amount of water; Wet hands first, then apply soap. If you are using piped water from a tap, make sure to switch the water off while you lather-up your hands. Rinse your hands until all the soap is visibly removed. In some countries, people reuse handwashing water to water flowers. It is also possible to design activities to show people that washing hands with soap consumes less water than they might expect by comparing it to another task that is performed regularly in the home e.g. making tea or coffee.
There are also some simple add-on handwashing technologies that reduce the flow of water allowing hands to be washed with a minimal amount of water. These include the SpaTap, the Oxfam Handy Wash Tap and the Dropas pictured below from left to right. Even a simple bucket-style container with a tap has been shown to use less water than pouring from a jug.
SpaTap - Source: Engineering for Change
Oxfam Handy Wash Tap - Source: Oxfam
Drop - Source: AltaDeva
Alternatively, there are simple DIY ways of restricting the stream of water. One example is using a jerry can and a nail as shown in the images below.
Source: London School of Hygiene and Tropical Medicine
Source: London School of Hygiene and Tropical Medicine
In 2021, Oxfam and Dunster House Ltd launched their novel handwashing kit for emergency settings, following a trial in refugee populations in Uganda and Tanzania. The handwashing station (see image below) is affordable, transportable and adjustable and includes a collection tray and mirrors.
Can I use greywater or water that is not clean for handwashing?
Yes, water for handwashing does not have to be as clean as water for drinking. Studies have shown that if you wash your hands with soap and relatively highly contaminated water, your hands will still be left clean. This shows just how effective soap is at removing pathogens from hands (see ‘our resource on how handwashing with soap removes pathogens’ for more information). So if water is scarce where you work, you may be able to convince people to keep the water they use for laundry, for example, and store this for handwashing use. However, it’s important to note that in many places, reusing water like this is not considered to be culturally acceptable, particularly if water is soapy.
How should hands be dried?
Hand drying plays an important role in getting clean hands and preventing recontamination. In high income settings paper towels or electric air dryers can be used to effectively dry hands. However, these are not available or feasible in many low- and middle- income settings so often people recommend just shaking hands dry. However, if people go straight back to their day-to-day activities after handwashing, this can be problematic, because wet hands tend to pick up more pathogens from the surfaces they touch. The good news is that a study in Zimbabwe found that drying hands on clean towels or even on dirty clothes can be more effective at removing any remaining bacteria from hands than simply air drying (shaking hands dry).