Homeopathy is a form of alternative medicine that treats patients with heavily diluted preparations that are thought to cause effects similar to the symptoms presented, first expounded by German physician Samuel Hahnemann in 1796. Homeopathic remedies are prepared by serial dilution with shaking by forceful striking ("succussing") after each step under the assumption that this increases the effect of the treatment; this process is referred to as "potentization". Dilution often continues until none of the original substance remains.
Apart from the symptoms of the disease, homeopaths use aspects of the patient's physical
and psychological state in recommending remedies. Homeopathic reference books known
as repertories are then consulted, and a remedy is selected based on the index of
symptoms. Homeopathic remedies are generally considered safe, with rare exceptions.
However, homeopaths have been criticized for putting patients at risk with advice
to avoid conventional medicine, such as vaccinations, anti-
Claims of homeopathy's efficacy beyond the placebo effect are unsupported by the
collective weight of scientific and clinical evidence. Supporters claim that studies
published in reputable journals support the efficacy of homeopathy; however, there
are only a handful of them, they are not definitive and they have not been replicated.
Homeopathic remedies generally contain few or no pharmacologically active ingredients, and for such remedies to have pharmacological effect would violate fundamental principles of science Modern homeopaths have proposed that water has a memory that allows homeopathic preparations to work without any of the original substance; however, the physics of water are well understood, and no known mechanism permits such a memory. The lack of convincing scientific evidence supporting homeopathy's efficacy and its use of remedies lacking active ingredients have caused homeopathy to be described as pseudoscience and quackery