>[!abstract] >Hormesis is a biological phenomenon in which exposure to a low dose of a stressor or toxin produces beneficial adaptive effects, while higher doses are harmful. Commonly observed with radiation, exercise, caloric restriction, and certain phytochemicals, hormesis reflects a biphasic dose–response curve: stimulation at low levels, inhibition or damage at high levels. It illustrates how organisms evolve resilience mechanisms that are activated by mild stress, enhancing repair, defense, and adaptation. The concept challenges linear "dose = harm" models and informs fields from toxicology and pharmacology to aging research and preventive medicine. >[!related] >- **North** (upstream): [[Toxicology]] >- **West** (similar): [[Antifragility]], [[Stress inoculation]] >- **East** (different): [[Linear no-threshold model]] (the assumption that any dose of a harmful agent is damaging, with no safe or beneficial level) >- **South** (downstream): [[Adaptive stress response]] (e.g., exercise-induced oxidative stress, caloric restriction, phytochemicals in plants)