Merck Manual

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Professional Version



Narda G. Robinson

, DO, DVM, MS, FAAMA, CuraCore Integrative Medicine & Education Center

Last full review/revision Aug 2013 | Content last modified Jun 2016

Homeopathy, a form of practice initiated in the late 18th century by the German physician Samuel Hahnemann, refers to treatment of disease with sometimes extreme dilutions of substances that in undiluted form might cause symptoms of that same disease; these substances supposedly promote healing. The substances are said to possess vital healing energies that are unchanged, or even strengthened, through the dilution process. Homeopathic remedies usually consist of lactose pills or liquids.

No known, or even credible, mechanism of action exists by which extremely dilute homeopathic preparations might have a therapeutic effect. Controlled studies have demonstrated that the homeopathic “provings”—sessions in which individuals record the symptoms caused by ingestion of the remedies—cannot distinguish between homeopathic dilutions and placebo. Indeed, no study has been able to distinguish homeopathic remedies from control solutions, by any method of analysis. As a result, most authorities consider that any clinical effects obtained from homeopathic remedies are actually placebo effects.


Although largely unsupported by research, homeopaths typically feel that their remedies can be prescribed for most medical conditions, including cancer. Reported veterinary uses have included inappropriate urination in cats; babesiosis, atopic dermatitis, idiopathic epilepsy, and paroxysmal tachycardia in dogs; fattening of, stillbirths, and diarrhea in pigs; postpartum fertility, mastitis, anestrus, and control of ticks in cattle; diarrhea in calves; salmonellosis in broiler chickens; and helminth parasitism in sheep.


Conditions for which regular medical treatment would provide a more meaningful diagnosis and effective treatment, and for which delay of proper care could prove injurious, should not be treated by homeopathy. Adjunctive homeopathic remedies, which may be prescribed as “complementary” treatments to more conventional therapies, have been shown to be no different from placebo in improving the quality of life of children with mild to moderate asthma when prescribed in addition to conventional treatment in primary care.

Adverse Effects:

Chances of homeopathic remedies causing direct toxicities are slight, given their extreme dilution. Homeopathic literature does describe a situation involving a transient worsening of signs called a symptom aggravation or healing “crisis.” Homeopaths may regard this as a treatment breakthrough and sign of impending improvement.

Some practitioners advocate giving homeopathic “vaccines” or nosodes instead of conventional vaccines to avoid perceived health risks of standard vaccines. However, homeopathic vaccines have consistently failed to provide reliable protection against infectious agents in scientific studies of both people and animals.


A preponderance of evidence indicates that effects of homeopathy cannot be distinguished from placebo. Therefore, the question remains whether it is ethical or misleading to offer an ineffective treatment to patients and their caregivers. The unscientific premise of homeopathy calls into question its legitimacy as a medical treatment.

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