As one of the most widely distributed and powerful environmental factors, light constantly affects physiological activities of living systems and participates in the regulation of various metabolic pathways. In recent years, with the acceleration of urbanization, artificial light at night has become an important cause of metabolic disorders. In contrast, the reasonable application of light color and its intensity also provide new therapeutic methods for diseases. Therefore, avoiding unreasonable light and utilize beneficial light become a great challenge for the whole society. At present, several studies have confirmed that light therapy has achieved remarkable efficacy in the treatment of cancer, depression, Alzheimer’s disease and other diseases. Choosing the best lighting conditions in daily life can further improve the living environment and health of human beings. The study of light and physiological homeostasis will become the hotspot in the future. This paper reviews the roles of detrimental light pollution and beneficial light therapy in the induction and treatment of diseases, respectively, and will provide theoretical support in choosing healthier light environment and developing the light as an effective therapeutic intervention on multiple diseases.