Hormesis within a mechanistic context

•A mechanistic basis of hormesis is provided.•Hormetic mechanisms are given within the context of receptor- and cell signaling-based pathways.•The quantitative features of the hormetic dose response are independent of mechanism.

This paper provides an assessment of the mechanistic foundations of hormesis and how such understandings evolved over the course of the past century. Particular emphasis is placed on recent developments particularly with respect to receptor-based and cell signaling-based pathways. Of particular importance is that the quantitative feature of the hormetic dose response are independent of mechanism.