Cost-effectiveness and benefit-cost analyses of promoting handwashing with soap: A systematic review

Background Promoting handwashing with soap reduces risk of diarrhoea by 30% and respiratory infections by 17%. Handwashing promotion in nonhealthcare settings is widely considered cost-effective, but there is no systematic review on this topic. To inform resource allocation decisions, we reviewed the state and quality of evidence regarding cost-effectiveness and benefit-cost of interventions promoting handwashing with soap in domestic, educational, and childcare settings globally. Methods and findings We searched Medline, Embase, Global Health, EconLit, and Web of Science for studies published from January 1, 1980 to September 3, 2025, as well as grey literature (PROSPERO CRD42021288727). We included full economic evaluations comparing the cost of two or more interventions with their outcomes. We included interventions promoting the practice of handwashing with soap, including those providing information, motivational campaigns, and/or handwashing facilities. We scored quality of reporting using the Consolidated Health Economic Evaluation Reporting Standards. We identified 15 studies of which 3 were in high-income countries. Five used empirical data collection to evaluate interventions actually implemented and 10 modelled from secondary data only. Amongst the 3 medium- or high-quality studies reporting cost per disability-adjusted life-year averted, estimates ranged from US$ 37 to 937 (2024 prices). Of these 3 estimates, 2 were cost-effective compared to plausible thresholds for the respective country. In the only medium- or high-quality benefit-cost study, the mean benefit-cost ratio was 2.1 with “medium” levels of handwashing adoption (40% of population) and adherence (50% of those adopting). Few studies measured or modelled adoption of handwashing over time, and none which focussed on diarrhoea also valued respiratory infections. Limitations of our review include that we excluded alcohol-based handrub interventions, and that there is high uncertainty about cost-effectiveness thresholds. Conclusions Promoting handwashing with soap is very likely to be cost-effective for interventions that successfully increase and sustain adoption of handwashing behaviours. More empirical studies are needed, especially those comparing multiple promotion options and valuing reductions in respiratory infections as well as diarrhoea.