Homeopathy

Homeopathy rests on two linked ideas set out by Samuel Hahnemann. The first, similia similibus curentur, or like cures like, holds that a substance capable of producing a set of symptoms in a healthy person can cure a sick person showing those same symptoms; Hahnemann arrived at the idea after taking cinchona bark, a source of quinine, and noting that it produced symptoms resembling the malaria it was used to treat. The second is potentization: homeopathic remedies are prepared by repeatedly diluting a substance, often in a ratio of one part in a hundred at each step, with vigorous shaking, or succussion, between dilutions. Many common homeopathic remedies are diluted well past the point, given by Avogadro's number, at which a dose is statistically likely to contain even a single molecule of the original substance; homeopathic theory holds that succussion imprints the substance's therapeutic pattern onto the diluting medium itself, a claim with no accepted basis in chemistry or physics.

In practice, a homeopathic consultation typically involves a detailed intake of the patient's physical and emotional symptoms, matched against a large reference literature, the materia medica, to select a single remedy believed to fit that individual's whole symptom picture rather than a named disease. Remedies are sold over the counter in many countries as well as prescribed by trained homeopaths, and the practice remains popular worldwide, particularly in parts of Europe and India, even as its proposed mechanism sits outside accepted science and its clinical trial record has not supported its specific claims.

Homeopathy has been tested in hundreds of clinical trials since the mid-twentieth century, and the pattern that has emerged is consistent: larger, higher-quality, better-blinded trials tend to show smaller effects, and the largest, most careful comparisons find no effect beyond placebo. The most widely cited of these is a 2005 meta-analysis published in The Lancet by Aijing Shang and colleagues, which compared 110 placebo-controlled homeopathy trials against 110 matched conventional-medicine trials and concluded that homeopathy's apparent clinical effects were consistent with placebo once study quality and size were taken into account; the accompanying editorial was titled 'The End of Homoeopathy.' Homeopathy researchers have disputed the specific eight-trial subset the paper's headline conclusion rested on, but later independent reviews, including government evidence checks, reached substantively the same conclusion.

That conclusion has had direct regulatory consequences. The United Kingdom's House of Commons Science and Technology Committee published its own review, Evidence Check 2: Homeopathy, in February 2010, concluding that homeopathy works no better than placebo, that the National Health Service should stop funding it, and that its products should not be licensed as medicines able to carry treatment claims without evidence of efficacy. Homeopathy's remedies are generally not toxic in themselves, since almost none contain any detectable active ingredient, so the practice's main documented harm is indirect: cases where patients have used it in place of effective treatment for serious conditions, with the delay in real care causing preventable harm.