Hormesis: Small Doses of Stress Are Healthy

Why can taking less antibiotics than prescribed be counterproductive? Why, if exercise produces large amounts of free radicals, does it slow down aging? In this article, we'll explain.
Hormesis: Small Doses of Stress Are Healthy
Sergio De Dios González

Reviewed and approved by the psychologist Sergio De Dios González.

Written by Edith Sánchez

Last update: 08 February, 2023

Hormesis is a fundamental concept in evolutionary theory. It means that exposure to a small dose of a certain harmful or toxic agent activates the body’s ability to adapt to higher doses of the same stimulus. As they say, what doesn’t kill you makes you stronger.

The concept of hormesis is applicable to different negative stimuli. It’s known that it works with poisons, heat, radiation, antibiotics, heavy metals, oxidants, exercise, and food restriction, among others. All these elements generate stress in the body, but in low doses, they become a kind of antidote to damage.

The topic of hormesis still generates debates among scientists. This isn’t so much because of its validity, but because of its scope. This same principle applies to psychological stress. It means that the reiterated state would prepare us to deal more successfully with highly stressful situations.

This is what hormesis consists of. It’s a word that comes from the Greek and means to stimulate. A high dose of almost everything kills, but a low dose is healthier than zero .”

-Dario Pescador-

Man with work stress
The hormesis process explains that the dosage of stress, not the stress itself, produces certain effects.


The concept of hormesis, as such, is new. However, it’s a principle that’s been recognized for centuries. The following story corroborates it. King Mithridates the Great, who ruled the Kingdom of Pontus a century before our era, was an expert in poisons.

From a very young age, he tried poisons of all kinds in extremely small quantities. He wasn’t the only one to carry out this practice, but he was one of the most famous. When he was defeated by Pompey, in what was his last battle, he tried to commit suicide with poison, but it had no effect. Therefore, he had to ask a mercenary to run him through with his sword.

The anecdote became so famous that today, this practice is known as mithridatism. In fact, in countries like Brazil and Australia, some people have achieved complete immunity to venom from snakes and vipers by following the same procedure as Mithridates. This provided the first evidence that hormesis was a reality.

It’s all a matter of method

The traditional approach against exposure to toxic agents or situations was to avoid them. However, the principle of hormesis contradicts this premise. There are many examples. One concerns heroin addicts. For someone who’s not an addict, a dose of just 200 milliliters of heroin would be lethal. But those who consume this substance on a regular basis can tolerate up to three times that dose.

A study claims that something similar has been observed among the survivors of the atomic bombs in Hiroshima and Nagasaki. Those near the point of impact were killed or severely hurt, or developed cancer in the years that followed. On the other hand, those who were further away experienced fewer cases of cancer than the Japanese population in general.

This leads to the Paracelsus thesis: “All things are poison, and nothing is without poison; the dosage alone makes it so a thing is not poison”. Likewise, it leads to a new premise that’s gradually gaining weight: stress is good for our health. The key lies in the dose. If there’s a great deal of it and it’s isolated, it can do damage. On the other hand, if it’s moderate and periodic, it seems to generate adaptive effects.

Stressed young japanese man
Stress in small doses can be adaptive.

Take advantage of hormesis

There are certain practices that generate stress to the body yet are healthy. Among them, is intermittent fasting. Likewise, exercise or a sudden change of temperature (heat/cold) that’s frequently used to heal injuries.

According to some studies, mitochondria is more resistant to oxidation when the level of free radicals increases. At first, this appeared to be contradictory but it’s now been scientifically verified. That’s why exercise, which causes stress to the body, helps slow down the aging process.

Finally, it’s important to emphasize that hormesis is only effective when the correct dose of radiation, toxins, exercise, fasting, etc. is used. A lower dose or frequency is harmful, as is a higher one. Therefore, it’s clear that frequent small doses of stress are healthy.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Bárcena, C., Mayoral, P., & Quirós, P. M. Chapter Two-Mitohormesis, an antiaging paradigm. International Review of Cell and Molecular Biology, 35-77.
  • Calabrese, E. J., & Baldwin, L. A. (2003). Hormesis: the dose-response revolution. The Selected Works of Edward J. Calabrese, 2.
  • Sutou, S. Low-dose radiation from A-bombs elongated lifespan and reduced cancer mortality relative to un-irradiated individuals. Genes and Environ 40, 26 (2018). https://doi.org/10.1186/s41021-018-0114-3

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.