A critical overview of homeopathy.

Homeopathy is a 200-year-old therapeutic system that uses small doses of various substances to stimulate autoregulatory and self-healing processes. Homeopathy selects substances by matching a patient's symptoms with symptoms produced by these substances in healthy individuals. Medicines are prepared by serial dilution and shaking, which proponents claim imprints information into water. Although many conventional physicians find such notions implausible, homeopathy had a prominent place in 19th-century health care and has recently undergone a worldwide revival. In the United States, patients who seek homeopathic care are more affluent and younger and more often seek treatment for subjective symptoms than those who seek conventional care. Homeopathic remedies were allowed by the 1939 Pure Food and Drug Act and are available over the counter. Some data--both from randomized, controlled trials and laboratory research--show effects from homeopathic remedies that contradict the contemporary rational basis of medicine. Three independent systematic reviews of placebo-controlled trials on homeopathy reported that its effects seem to be more than placebo, and one review found its effects consistent with placebo. There is also evidence from randomized, controlled trials that homeopathy may be effective for the treatment of influenza, allergies, postoperative ileus, and childhood diarrhea. Evidence suggests that homeopathy is ineffective for migraine, delayed-onset muscle soreness, and influenza prevention. There is a lack of conclusive evidence on the effectiveness of homeopathy for most conditions. Homeopathy deserves an open-minded opportunity to demonstrate its value by using evidence-based principles, but it should not be substituted for proven therapies.