Update on hormesis and its relation to homeopathy.

Introduction: Hormesis is a dose-response relationship characterized by a biphasic dose response to stressors with a low dose stimulation and a high dose inhibition. The first systematic description of hormesis appeared toward the close of the 18th century by the German pharmacology professor Hugo Schulz. The stressor agent can be any agent or factor capable of causing a deleterious effect. The biological systems can be diverse: bacteria, fungi, algae, yeasts, animals, humans, protozoa and plants. The range of endpoints covers longevity, reproduction, cancer, survival, growth, metabolic effects and others. Hormesis is a nonspecific phenomenon, which can occur in any biological system and can be caused by any stressor. It is quantifiable and reproducible. The apparent similarity between the basic principle of hormesis and homeopathy's Similia Principle, together with the homeopathic claim that hormesis validates homeopathy caused its marginalization, and its rejection during the past century by central figures in pharmacology. Recent years have seen a slight renaissance in the conventional scientific attitude towards hormesis.

Method: We compared hormesis and homeopathy.

Result: There is no convincing evidence of similarity between these two systems. Moreover, there are several crucial differences between them, which seem to refute any idea that they stem from the same root. This paper discusses these differences. The rejection of hormesis on grounds of its similarity to homeopathy is unjustified.

Conclusion: The authors suggest exploring the differences between both systems. Such exploration may answer the key question of whether they do indeed share a root or embrace the same principles. Such exploration may also spur research within both systems to answer further open questions.