The dose makes the poison
All things are poison, and nothing is without poison, the dosage alone makes it so a thing is not a poison.
"The dose makes the poison" (Latin: sola dosis facit venenum) is an adage intended to indicate a basic principle of toxicology. It is credited to Paracelsus who expressed the classic toxicology maxim "All things are poison, and nothing is without poison, the dosage alone makes it so a thing is not a poison." This is often condensed to: "The dose makes the poison" or in Latin, "Sola dosis facit venenum". It means that a substance can produce the harmful effect associated with its toxic properties only if it reaches a susceptible biological system within the body in a high enough concentration (i.e., dose).
The principle relies on the finding that all chemicals—even water and oxygen—can be toxic if too much is eaten, drunk, or absorbed. "The toxicity of any particular chemical depends on many factors, including the extent to which it enters an individual’s body." This finding provides also the basis for public health standards, which specify maximum acceptable concentrations of various contaminants in food, public drinking water, and the environment.
However, there is no linear relationship and also more to chemical toxicity than the acute effects caused by short-term exposure. Relatively low doses of contaminants in water, food, and environment can already have significant chronic effects if there is a long-term exposure. Many pollutants, drugs, and natural substances adhere to this principle by causing different effects at different levels, which can as a result lead to health standards that are either too strong or too weak.
Generally the effects of different doses can be very different at different levels (not only bigger and smaller impacts depending on dose). Very low doses of some compounds can even induce stronger toxic responses than much higher doses as well as just different impacts.
- "Die dritte Defension wegen des Schreibens der neuen Rezepte," Septem Defensiones 1538. Werke Bd. 2, Darmstadt 1965, p. 510 (full text)
- The Dose Makes the Poison on Chemsafe at Yale Archived 2011-02-02 at the Wayback Machine.
- Nancy Trautmann: The Dose Makes the Poison--Or Does It?, Bioscience 2005, American Institute of Biological Sciences
- Pete Myers, Ph.D. and Wendy Hessle, "Does 'the dose make the poison?'", ourstolenfuture.org