Environmental medicine studies the interfaces among chemicals, food and inhalants in the environment and the biological function of the individual. It was founded in the 1940s by Theron Randolph, who, along with others, developed a new model and associated clinical principles that would help a physician to diagnose an illness by studying the environmental factors affecting the patient. Today, environmental medicine is practised by more than 3,000 practitioners the world over.

Environmental medicine acts on three basic concepts: adaptation, spreading phenomenon, and switch phenomenon. Diagnosis involves a detailed chronological history. Individual susceptibility is related to genetics, nutritional status, effectiveness of detoxification pathways, total chemical and allergic load