Does it work?
Yes, a little. The Cochrane review (opens in a new tab) of 78 trials found that hand hygiene programs probably cut acute respiratory illness by about 14%. For flu-like illness and lab-confirmed flu, the results were too uncertain to say either way.
Most trials ran in schools, childcare and homes, and outside epidemics, so there is less evidence for how well it works during an outbreak. Many of the programs handed out soap and taught washing, so the review can’t separate the washing from the program. People also wash less than they say they do.
One layer of several
Washing deals with what’s on your hands, not the virus hanging in the air. Pair it with ventilating, filtering and far UV-C. It helps prevent infection; it won’t treat one.
Soap or sanitizer?
Soap, when you can. It lifts microbes off your skin and the water rinses them away, and it is the best way to remove all types of microbes and chemicals (opens in a new tab). Sanitizer kills them instead, and it’s what you reach for when there’s no sink.
Use soap when your hands are visibly dirty or greasy, after the toilet, and around norovirus, which sanitizer does not work well against (opens in a new tab). Otherwise, a sanitizer with at least 60% alcohol, rubbed in for about 20 seconds until dry, is a good stand-in.
How to wash
- Wet your hands and add soap.
- Scrub for at least 20 seconds: palms, backs, between fingers, thumbs, fingertips and under nails. That is about two rounds of “Happy Birthday”, as the NHS (opens in a new tab) puts it.
- Rinse under running water.
- Dry with a clean towel or air dry.
Pick your moments
Wash at the moments that count most (opens in a new tab): after the toilet or changing a diaper, before and after handling raw food, before eating, after blowing your nose, sneezing or coughing, before and after treating a wound, and after touching animals.
Caution
Home-made HOCl is for cleaning surfaces only. For hands, use soap or sanitizer.
Research
- Cochrane review: physical interventions to interrupt or reduce the spread of respiratory viruses (opens in a new tab) (Jefferson et al., 2023). Funded by the UK’s National Institute for Health and Care Research.
- Living evidence synthesis: hand hygiene to reduce transmission of respiratory infectious diseases in the community (opens in a new tab) (Public Health Agency of Canada, August 2024).
- Mo et al. (2022) (opens in a new tab), a pooled analysis of six trials. One more hand hygiene event a day went with a 3% lower daily probability of acute respiratory infection, within a range that includes no effect.
- Find related studies in the research collection.