Reactive oxygen species (ROS) and free radicals work to maintain homeostasis in the body, and excessive ROS can damage the body's proteins, lipids, and DNA. Oxidative stress (OS) is the term commonly used to describe the imbalance between the generation of free radicals in the body and the ability of cells to counteract them. Accumulation of OS is aging, and OS also represents an important role for physiological homeostasis. Deviations from sustained redox signaling homeostasis are also now known to cause disease. The important relationship between OS and various diseases has been established, and OS is now at the forefront of research to elucidate pathogenesis. Despite this, so-called antioxidant therapy for diseases is still not widely used.

There are many types of ROS and free radicals, and each type has different properties. The widespread use of antioxidant therapy requires a level of antioxidants that can counter these. It is not clear whether OS induced the disease or was secondary to tissue damage derived from the onset of the disease. Although the exact role of oxidants in disease pathogenesis is not always clear, OS has received significant attention as a factor in human disease and is the focus of extensive research. This field will contribute to the prevention and treatment of diseases in the future.