Abstract This article provides a comprehensive review of hormesis, a dose-response concept that is characterized by a low dose stimulation and a high dose inhibition. The article traces the historical foundations of hormesis, its quantitative features, mechanistic foundations and its risk assessment implications. The article indicates that the hormesis dose-response is the most fundamental dose-response, significantly outcompeting other leading dose-response models in large scale head-to-head evaluations. The hormetic dose-response is highly generalizable, being independent of biological model, endpoint measured, chemical class, and inter-individual variability. Hormesis also provides a framework for the study and assessment of chemical mixtures, incorporating the concept of additivity and synergism. Since the hormetic biphasic dose-response represents a general pattern of biological responsiveness it is expected that it will become progressively more significant within toxicological evaluation and risk assessment practices as well as having numerous biomedical applications.

Keywords: Hormesis; J-shaped; U-shaped; Dose-response; Biphasic