In the fields of biology and medicine, hormesis is defined as an adaptive response to a moderate (usually intermittent) stress. It is a process in which exposure to a low dose of a chemical agent or environmental factor, that is damaging at higher doses, induces a beneficial effect. Hormesis is also known as "preconditioning” and “adaptive stress response". Hormesis is a fundamental concept in our survival: to avoid extinction, humans developed mechanisms to cope with the environmental stressors and harness the benefits from potentially toxic environmental hazards.
Although the term is unfamiliar to many, but the applications of hormesis are common. For example: exercise (especially vigorous exercise), intermittent dietary restriction (intermittent fasting), exposure to extremes of temperature (cold showers, saunas) and exposures to low doses of certain compounds can trigger cellular mechanisms which ultimately lead to better health. These responses are mediated by a whole host of enzymes, hormones and signalling molecules operating at the sub-cellular level.
An interesting "cross -protection" observation in studies of hormesis is that exposure to low levels of one type of hormetic agent can protect cells against more than one type of stress. For example, exposure of cells to mild heat stress can protect them from being damaged by cyanide (Li et al., 2002).
Several studies confirmed hormesis as a mechanism responsible for the health benefits of a variety of lifestyle interventions. For example: Hoermesis underpins the benefits of High Intensity Interval Training (HIIT), which increases the resistance of musculoskeletal and cardiovascular systems to injury and disease.
In the field of alternative medicine, hormesis has been the principle underlying many of well-known therapies. For example, hormesis is implicated in the actions of acupuncture (Staud and Price, 2006). It is also implicated in a variety of other less well established complementary therapies such as Kambo, Thermotherapy, Cryotherapy etc. Hormesis also underpins ozone therapy, where a calculated doe of ozone produces beneficiary responses whereas high or low doses produce unwanted side effects or no effect at all respectively.