Homeopathy is a form of substitute medicine first described by Samuel Hahnemann in the 18th century. Homeopathic practitioners preserve that sick person can be treated using a stuff that can create, in a healthy person, symptoms similar to those of the sickness. According to homeopaths, serial strength, with trembling between each dilution, removes the poisonous effects of the "remedy" while the qualities of the substance are retained by the diluent. The end product is often so diluted that it is indistinguishable from pure water, sugar or alcohol. Practitioners choose treatments according to a patient discussion that explores the physical and psychological state of the patient, both of which are considered significant to selecting the remedy.

Claims to the effectiveness of homeopathic treatment away from the placebo effect are unsupported by the communal weight of scientific and clinical evidence. Common homeopathic training are diluted beyond the point where there is any probability that molecules from the original solution are present in the final product; the claim that these treatments still have any pharmacological effect is thus scientifically unlikely and violates basic principles of science, comprising the law of mass action.