Advice to ‘wash your hands’ thoroughly - 20-seconds of lathering with soap - may seem easy to follow, yet millions globally cannot reliably access the water and soap necessary for handwashing. Moreover, more frequent handwashing places further demands on already limited water supplies, exacerbating the challenges faced by communities in water scarce areas. Climate change, population growth, and displacement of people present additional challenges by altering water availability, accessibility, and demand.