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. Few studies investigate handwashing efficacy against enveloped viruses, and a recent 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. The review included studies on similar viruses, but currently there are no studies on SARS-CoV-2.
Given the lack of evidence around most of these soap alternatives, they should not be promoted during the COVID-19 pandemic 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 the COVID-19 pandemic:
- Ash - Ash is the most commonly used alternative to soap. Currently there is poor evidence on the effectiveness of ash for hand cleaning and no experimental evidence that it can kill or remove viruses, including SARS-CoV-2. Ash is likely to work because it is abrasive, and it creates an alkaline solution which may inactivate viruses. Despite a lack of evidence on the use of ash for handwashing, the WHO has recommended that ash should be used as a last resort in situations where soap is not available as it is likely to be more efficacious than handwashing with water only. 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. 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 at this time. 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.
At the moment 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.
Author: Ayesha Chugh and Sian White
Reviewers: Amy Pickering, Marlene Wolfe, Julia Rosenbaum
Last updated 07.08.2020