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By Steven Novella, MD, Assistant Professor of Neurology, Yale University School of Medicine

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Patient Education

Developed in Germany in the late 1700s, homeopathy is a medical system based on the principle that like cures like (the law of similars). A substance that, when given in large doses, causes a certain set of symptoms is believed to cure the same symptoms when it is given in minute to nonexistent doses. The minute dose is thought to stimulate the body’s healing mechanisms.

Treatments are based on the patient’s unique characteristics, including personality and lifestyle, as well as symptoms and general health. Homeopathy aims to restore the flow of the body's innate life force (vitalism); it is not based on principles of chemistry or physiology.

Remedies used in homeopathy are derived from naturally occurring substances, such as plant extracts and minerals. Extremely low concentrations are prepared in a specific way. The more dilute the homeopathic remedy, the stronger it is considered to be. Many solutions are so dilute that they contain no molecules of the active ingredient. For example, 30C dilution is diluted 1 to 100 in 30 serial dilutions, resulting in a final dilution of 1 x 1060.

Homeopathic products are available over the counter or by prescription.

Regulation of Homeopathy

Unlike herbal and nutritional supplements, homeopathic remedies are regulated by the FDA. Only homeopathic remedies that are approved by the FDA can be manufactured. Because so little active ingredient is left after dilution, active ingredients are tested before dilution.

The FDA exempts homeopathic remedies from several requirements that exist for other drugs:

  • The identity and strength of each active ingredient do not have to be confirmed by a laboratory before the remedy is distributed.

  • Manufacturers of homeopathic products are not required to provide evidence of efficacy.

  • Homeopathic remedies have been temporarily exempted from limits on the amount of alcohol (the usual diluent) that they can contain.

However, the label is required to list the following:

  • Manufacturer

  • The label “homeopathic”

  • At least one indication

  • Instructions for safe use

  • Unless specifically exempted, the active ingredient and degree of dilution

Evidence for Homeopathy

The principles of homeopathy—like cures like and diluting makes preparations stronger—have no scientific basis. Expecting a preparation diluted so much that it has no active ingredient to have physiologic effects other than those of a placebo is biologically and chemically implausible. However, some homeopathic preparations do contain active ingredients in concentration sufficient to have physiologic effects (eg, Zicam, which contains a measurable amount of zinc).

Efficacy of homeopathic remedies for various disorders has been extensively studied. A 2010 analysis1 of systematic reviews found that homeopathy is no more efficacious than placebo for any indication, as did the United Kingdom's House of Commons Science and Technology Committee2 after an exhaustive review of systematic reviews and meta-analyses of homeopathy (2010). The Australian government's exhaustive review of the clinical evidence for homeopathy3 (2013) found that for 61 indications, there was evidence of lack of efficacy for homeopathy, and for another 7 indications, there was no good-quality evidence.

Proponents often cite the preliminary evidence in 3 studies4 published in 2003 supporting the efficacy of homeopathy for diarrhea in children. However, an independent review of that evidence found it unconvincing, and a larger, more rigorous follow-up study5 in 2006 concluded that homeopathy did not effectively treat diarrhea in children. Critics also point out that because all 3 studies were done by the same researcher, there has been no independent replication.

Uses of Homeopathy

Homeopathy is commonly used in Europe and India, largely because of a long history of use; as a result, the practice has become part of the culture.

Homeopathy has been used to treat various disorders, such as allergies, rhinitis, digestive problems, musculoskeletal pain, and vertigo.

Possible Adverse Effects

Homeopathy is well-tolerated and has few risks; rarely, an allergic or toxic reaction occurs.

A 2012 review1 of reported cases of adverse effects identified 38 reports involving 1159 patients. Adverse effects included

  • Direct reactions to homeopathic treatments, presumably due to active ingredients

  • Indirect harm caused by substituting homeopathy for effective conventional treatment

Conventional clinicians should not assume that a homeopathic remedy taken by a patient is biologically inactive and thus could not have adverse effects. Also, some homeopathic remedies contain other active ingredients that can have physiologic effects. Whether patients are taking homeopathic remedies may be unclear because patients often use the term homeopathic erroneously in reference to a dietary supplement they are taking. Also, the FDA allows many medicinal herbs to be registered and labeled as homeopathic if they undergo a particular pharmaceutical process.

Pearls & Pitfalls

  • Do not assume homeopathic remedies are biologically inactive; although the ingredients in homeopathic remedies are usually so dilute that they have no potential for harm, some remedies do contain ingredients in amounts that can have physiologic effects.

  • 1Posadzki P, Alotaibi A, Ernst E: Adverse effects of homeopathy: a systematic review of published case reports and case series. Int J Clin Pract 66(12):1178–88, 2012.

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