Hormesis is classified as a dose-response phenomena characterised by low-dose stimulation and high-dose restriction, and has been recognised as exhibiting an over compensation for mild environmental factors. The beneficial effects of modest stress on ageing and longevity have been investigated for many years. A phenomenon in which a hazardous chemical delivers stimulating and positive effects to living organisms when the quantity of the detrimental substance is modest. The hormetic dosage response is extremely generalizable, being independent of biological model, endpoint measured, chemical class, and interindividual variability. Hormesis also provides a framework for the research and assessment of chemical mixtures, encompassing the concept of additivity and synergism. The substantial weakening of various hormetic mechanisms in the aged may drastically limit the capacity to respond effectively to multiple.