Homeopathy works

Homeopathy works
	FALSE
	"Homeopathic remedies, made by diluting substances in water many times over, can treat and cure illnesses because "like cures like" and water retains a "memory" of the substances once dissolved in it."
Domain	Health & Medicine
Tactic	Pseudoscience / Junk Science;
Era	Historical
First seen	1796
Origin	The German physician Samuel Hahnemann, who set out the principles of homeopathy in 1796 and in his Organon of the Healing Art (1810)
Last reviewed	2026-10-27
	Further reading: books on Health & Medicine

The claim that homeopathy works underpins a global industry selling remedies worth billions of dollars a year. Homeopathy holds that a substance that causes symptoms in a healthy person can cure similar symptoms in a sick person, and that diluting the substance repeatedly makes it more powerful. Many remedies are diluted so far that not a single molecule of the original substance is likely to remain. Large systematic reviews by national health bodies have found no reliable evidence that homeopathy works better than a placebo for any health condition. Its central principles also conflict with basic chemistry and physics. Homeopathy can cause harm when people use it instead of effective treatment.

The claim

Homeopathy rests on two main ideas. The first, "like cures like," holds that a substance that produces symptoms in a healthy person, such as onion causing watery eyes, can treat those symptoms in illness. The second, the "law of infinitesimals," holds that diluting a substance and shaking it vigorously between dilutions, a process called succussion, increases its healing power while removing its toxicity.

Dilutions are labeled by scale. A "C" dilution means one part substance to 99 parts water. A remedy labeled 30C has been diluted this way 30 times, a total dilution of one part in 10 to the power of 60. Remedies are sold as liquids or as sugar pills onto which the diluted liquid has been dropped. Proponents argue that water retains a "memory" of the substance, explaining how a remedy with no remaining molecules can still have an effect.

Origin

Samuel Hahnemann developed homeopathy in the 1790s, at a time when mainstream medicine relied on bloodletting, purging and toxic compounds such as mercury. In that context, homeopathy's harmless remedies may have produced better outcomes simply by doing nothing, allowing patients to recover naturally. Homeopathy spread across Europe and the United States in the nineteenth century and remains popular in parts of Europe and in India, where it is officially recognized as a system of medicine.

What the evidence shows

Chemistry. Beyond a dilution of about 12C, which exceeds Avogadro's number, it is unlikely that even one molecule of the original substance remains. A 30C remedy would require drinking an amount of water vastly larger than the Earth to have a reasonable chance of consuming a single molecule.
Water memory. In 1988 the French scientist Jacques Benveniste published a paper in Nature claiming that antibodies diluted beyond the point where any molecules remained still had biological effects. Nature published it with an unusual editorial caveat and sent an investigative team, including editor John Maddox and the magician and skeptic James Randi, to observe repeat experiments under controlled conditions. When the experiments were blinded, the effect disappeared. No reliable evidence for water memory has emerged since.
Clinical trials. A 2005 meta-analysis in The Lancet by Aijing Shang and colleagues compared homeopathy trials with conventional medicine trials and concluded that the clinical effects of homeopathy were compatible with placebo effects.
National reviews. In 2010 the UK House of Commons Science and Technology Committee concluded that homeopathic products perform no better than placebos. In 2015 Australia's National Health and Medical Research Council reviewed evidence from more than 1,800 studies and found no health conditions for which there was reliable evidence that homeopathy was effective. In 2017 NHS England recommended that doctors stop prescribing homeopathic remedies.

Supporters point to individual studies with positive results. These are typically small, poorly controlled or unreplicated; when trials are larger and better designed, apparent effects tend to shrink toward zero.

Harms

Homeopathic remedies themselves are usually harmless because they contain little or nothing. The danger arises when people use them instead of effective treatment for serious conditions, delay seeing a doctor, or rely on homeopathic "vaccines" or malaria prevention. There have also been cases of poorly manufactured products containing measurable amounts of toxic substances. In 2016 the US Food and Drug Administration warned against homeopathic teething products for infants after reports of adverse events, and laboratory testing found inconsistent amounts of belladonna in some products.

Why it persists

Placebo and natural recovery. Many conditions improve on their own, and people credit whatever treatment they were using.
Long consultations. Homeopaths often spend more time listening to patients than conventional doctors, which can make patients feel better.
Regulatory status. In some countries homeopathic products are sold in pharmacies alongside real medicines, lending them credibility.
Appeal of the natural. Homeopathy is marketed as gentle and natural, although its principles have nothing to do with natural medicine.

Lessons for readers

Ask whether a treatment has been shown to work in well-designed, controlled trials, not just testimonials.
Check the dilution. A remedy diluted beyond 12C almost certainly contains none of the listed ingredient.
Being sold in a pharmacy does not mean a product has been shown to work.
Natural recovery and placebo effects can make any treatment seem effective.
Do not replace proven treatment for serious illness with homeopathy.

Sources

Aijing Shang et al., "Are the clinical effects of homoeopathy placebo effects? Comparative study of placebo-controlled trials of homoeopathy and allopathy," The Lancet 366, no. 9487 (2005).
House of Commons Science and Technology Committee, Evidence Check 2: Homeopathy (2010).
National Health and Medical Research Council (Australia), NHMRC Information Paper: Evidence on the Effectiveness of Homeopathy for Treating Health Conditions (2015).
John Maddox, James Randi and Walter W. Stewart, "'High-dilution' experiments a delusion," Nature 334 (1988).
US Food and Drug Administration, warnings concerning homeopathic teething tablets (2016–2017).