Hygiene is the concept of preventing disease and maintaining and improving health. Together with environmental medicine, it constitutes a subject concerned with the effects on health of risks such as climatic factors, radiation, hazardous substances and foreign bodies in the environment and in food. It examines these factors on-site and in the laboratory, clarifies the mode of action and evaluates risks  from a physician’s point of view. It formulates basic principles for protecting health and develops preventative measures for the general public and for individuals, e.g. epidemiology, combating infectious diseases. The basic areas of hygiene are: hygiene at work, social hygiene, environmental hygiene and hospital hygiene. The latter two areas are becoming increasingly important as a result of climate change and the sharp rise in nosocomial infections. Hygiene is closely linked with healthcare policy and health economics -  it can be considered a higher-level term in preventative healthcare measures, or indeed as primary preventive medicine.