·  What it is
Homeopathic medicine is premised on the idea that human beings naturally possess a vital healing energy; homeopathic remedies are designed to foster and stimulate this self-healing capacity. Homeopathic medicines are made from highly diluted natural substances, such as plants, animals, minerals, and insects. Recurrent headaches, arthritis, allergies, autoimmune disorders, bacterial and viral infections, as well as the common cold, are among the illnesses most commonly treated by homeopathic remedies.

·  How it works
The fundamental premise of homeopathy is "like cures like." Homeopathic medicines consist of extremely small doses of an agent (usually a natural substance such as a plant, mineral, or animal) which, if taken in larger doses, would actually cause the symptom the patient is looking to alleviate. For example, highly diluted ipecac, which is conventionally used to induce vomiting, is administered orally as a homeopathic remedy to cure nausea. Homeopathic remedies are available as tablets, pills or in liquid form.

·  What critics say
Critics of homeopathy argue that homeopathic medicine is scientifically impossible. Aside from the seemingly illogical approach of taking medicine that would induce symptoms rather than relieve them, critics point out that homeopathic medicines are so dilute that virtually none of the active substance could remain in the tincture or pill taken by the patient. Even if the substance could work, they argue, the patient isn't receiving any.

Read more about the controversy over homeopathy in excerpts from FRONTLINE's interviews with NCCAM director Stephen Straus, Harvard University's Tom Delbanco and David Eisenberg and medical historian James Whorton.

·  Scientific research findings
According to NCCAM, the numerous research studies on homeopathy have produced contradictory results. Some clinical studies have found homeopathy to be more effective than a placebo; others have not. Meta-analyses comparing the findings of dozens of these studies are similarly inconclusive. Although no meta-analysis of the literature has found homeopathic medicine to be definitively effective, three studies did find some positive results which were not attributable to the placebo effect.

Authors of many of the meta-analyses noted that conclusively evaluating the existing research is difficult, because the clinical data available is often flawed or unreliable.

For more discussion of the research, see this fact sheet from NCCAM.

·  Where to find more information

· Questions and Answers on Homeopathy from NCCAM Information on homeopathic treatments, the history of homeopathy, the controversy over scientific evidence and more.

· National Center for Homeopathy (NCH) The NCH is a non-profit dedicated to educating the public about homeopathy. The NCH site provides detailed information on homeopathy, a link to a database of studies, and a directory to find a homeopath. You can also get connected to a local study group in your area.

· North American Society of Homeopaths (NASH) NASH is a professional association of registered homeopaths. The NASH website provides a directory of registered homeopaths, as well as links to the organization's journal and newsletter.