Cell biology and proposed mechanisms
Hormesis
Hormesis describes a dose-response pattern in which a small dose of something has the opposite effect to a large dose — typically stimulating or protective at low exposure, harmful at high exposure. It is a real and studied phenomenon in toxicology, pharmacology and exercise physiology.
Also called hormetic dose response, biphasic dose response, mitohormesis
The shape of the curve
A hormetic dose response is not a straight line. Plot effect against dose and you get a modest benefit at low doses, crossing zero, then harm as the dose rises. Hormesis: a fundamental concept in biology, Microbial Cell (2014) by Edward Calabrese, argues that this pattern is highly generalisable across species, endpoints and agents. Calabrese is the field’s leading advocate; the existence of hormetic curves is not in dispute, though the claim that hormesis is the default dose-response model remains debated in regulatory toxicology.
Real examples
Exercise is the clearest one. Moderate exercise increases reactive oxygen species and, through that, improves insulin sensitivity and raises the body’s own antioxidant enzymes. Antioxidants prevent health-promoting effects of physical exercise in humans, PNAS (2009), showed that vitamin C and E supplements abolished those gains — the authors describe this as mitohormesis. Radiation adaptive responses and caloric restriction are others.
What it explains
Hormesis explains why a low dose of an oxidant might help where a high dose harms. That is the argument for controlling ozone output rather than maximising it, and Sagai and Bocci make exactly this comparison with exercise in Medical Gas Research (2011).
Showing that a particular exposure is hormetic takes a full dose-response curve with several doses below the no-effect level, not a single dose that appeared to help. The principle is general; the numbers are specific to whatever is being studied.
Why it matters here
Hormesis is the general principle behind the idea that a controlled dose is the point — for ozone output settings and for light dosing alike. It is a genuine, well-studied phenomenon.