This article discusses the importance of behaviour change in public health and provides insights into designing and evaluating behaviour change interventions. It explores the impact of hand washing on health and the role of social, physical, and cognitive determinants in changing behaviour. The article also introduces the Transtheoretical Model and other strategies for behaviour change. It provides information on measuring outcomes and evaluating the success of interventions. Additionally, it discusses the influence of hand washing on the physical and social aspects of health. References and resources for further study are included.