[6][7] These include the five critical times during the day where washing hands with soap is important to reduce fecal-oral transmission of disease: after using the toilet (for urination, defecation, menstrual hygiene), after cleaning a child's bottom (changing diapers), before feeding a child, before eating and before/after preparing food or handling raw meat, fish, or poultry.

[11] There are five critical times during the day where washing hands with soap is important to reduce fecal-oral transmission of disease: after using the toilet (for urination, defecation, menstrual hygiene), after cleaning a child's bottom (changing diapers), before feeding a child, before eating and before/after preparing food or handling raw meat, fish, or poultry.

[20] In developing countries, childhood mortality rates related to respiratory and diarrheal diseases can be reduced by introducing simple behavioral changes, such as hand washing with soap.

[21] Interventions that promote hand washing can reduce diarrhoea episodes by about a third, and this is comparable to providing clean water in low income areas.

[23] Handwashing with soap is the single most effective and inexpensive way to prevent diarrhea and acute respiratory infections (ARI), as automatic behavior performed in homes, schools, and communities worldwide.

[10] A 2012 Danish study found that excessive hand washing can lead to an itchy, flaky skin condition known as contact dermatitis, which is especially common among health-care workers.

[41] Dissenting, a 2011 meta-analysis in the Journal of Food Protection argued that when properly formulated, triclosan can grant a small but detectable improvement, as can chlorhexidine gluconate, iodophor, or povidone.

[45] Contrary to popular belief, scientific studies have shown that using warm water has no effect on reducing the microbial load on hands.

The front and back of both hands and between and the ends of all fingers must be rubbed for approximately 30 seconds until the liquid, foam or gel is dry.

Alcohol-based hand sanitizers are almost entirely ineffective against norovirus (or Norwalk) type viruses, the most common cause of contagious gastroenteritis.

[52] The increasing use of these agents is based on their ease of use and rapid killing activity against micro-organisms; however, they should not serve as a replacement for proper hand washing unless soap and water are unavailable.

[9] One concern is that if the soil or ash is contaminated with microorganisms it may increase the spread of disease rather than decrease it,[57] however, there is also no clear evidence to determine the level of risk.

[58] Various low-cost options can be made to facilitate hand washing where tap-water and/or soap is not available e.g. pouring water from a hanging jerrycan or gourd with suitable holes and/or using ash if needed in developing countries.

[59] In situations with limited water supply (such as schools or rural areas in developing countries), there are water-conserving solutions, such as "tippy-taps" and other low-cost options.

[60] A tippy-tap is a simple technology using a jug suspended by a rope, and a foot-operated lever to pour a small amount of water over the hands and a bar of soap.

Organizations attempting to prevent infection transmission in these environments have started using programmed washing cycles that provide sufficient time for scrubbing the hands with soap and rinsing them with water.

Combined with AI-powered software, these technological advancements turn the hand-washing process into digital data, allowing individuals to receive insights and improve their hand hygiene practices.

Specifically, the World Health Organization recommends that everyone "frequently clean [their] hands..." and "dry [them] thoroughly by using paper towels or a warm air dryer."

A growing volume of research suggests paper towels are much more hygienic than the electric hand dryers found in many public toilets.

"[2] Jet-air dryers were found to be capable of blowing micro-organisms from the hands and the unit and potentially contaminating other users and the environment up to 2 metres (6.6 feet) away.

[62]: 27 Medical hand-washing became mandatory long after Hungarian physician Ignaz Semmelweis discovered its effectiveness (in 1846) in preventing disease in a hospital environment.

[73] Medical hand-washing is for a minimum of 15 seconds, using generous amounts of soap and water or gel to lather and rub each part of the hands.

The New England Journal of Medicine reports that a lack of hand-washing remains at unacceptable levels in most medical environments, with large numbers of doctors and nurses routinely forgetting to wash their hands before touching patients, thus transmitting microorganisms.

[44] A relevant review was conducted by Whitby et al.[79] Commercial devices can measure and validate hand hygiene, if demonstration of regulatory compliance is required.

[88] Hand washing at a global level has its own indicator within Sustainable Development Goal 6, Target 6.2 which states "By 2030, achieve access to adequate and equitable sanitation and hygiene for all and end open defecation, paying special attention to the needs of women and girls and those in vulnerable situations.

[87] The corresponding Indicator 6.2.1 is formulated as follows: "Proportion of population using (a) safely managed sanitation services and (b) a hand-washing facility with soap and water" (see map to the right with data worldwide from 2017)."

[94] The importance of hand washing for human health – particularly for people in vulnerable circumstances like mothers who had just given birth or wounded soldiers in hospitals – was first[95][non-primary source needed] recognized in the mid 19th century by two pioneers of hand hygiene: the Hungarian physician Ignaz Semmelweis who worked in Vienna, Austria and Florence Nightingale, the English "founder of modern nursing".

[citation needed] The outbreak of swine flu in 2009 and the COVID-19 pandemic in 2020 led to increased awareness in many countries of the importance of washing hands with soap to protect oneself from such infectious diseases.

[citation needed] Research indicates that the COVID pandemic shifted social norms regarding hand washing, making it more prevalent worldwide.

It originates from the bible passage in Matthew where Pontius Pilate washed his hands of the decision to crucify Jesus Christ, but has become a phrase with a much wider usage in some English communities.