Homeopathy
"Like Cures Like" and the Vanishing Dose
Evidence grade 1 of 5, Refuted. Read how the Atlas grades evidence.
The scientific verdict is unusually clear and consistent. Large, careful reviews by major authorities have repeatedly found homeopathy performs no better than placebo. Australia's NHMRC, after examining evidence across 61 conditions (2015), concluded there are no health conditions for which there is reliable evidence that homeopathy is effective; systematic reviews of systematic reviews have found no remedy and no condition for which homeopathy is convincingly different from placebo; and Cochrane reviews (e.g., for childhood respiratory infections) have found no consistent benefit. Proponents cite selected positive trials and laboratory claims, but these are generally small, lower-quality, inconsistent, or unreplicated, and do not overturn the overall picture. The honest framing: homeopathy is implausible on basic physical grounds and, across the best evidence, indistinguishable from placebo. Its remedies are inert; its consultations and rituals can nonetheless produce real placebo effects, which is a separate matter from the remedies working.
Reference only. Not medical advice.
What can go wrong
The remedies themselves are usually harmless, because past about a 12C dilution they are materially water, alcohol, or sugar. The serious dangers are indirect. The gravest is delay or replacement of effective care: relying on homeopathy for serious or urgent conditions, or rejecting vaccines in favor of homeopathic 'nosodes' that do not protect against disease, can lead to preventable harm. In 2009 the WHO advised against using homeopathy to treat HIV, TB, malaria, influenza, and infant diarrhoea. A rarer physical risk is an improperly prepared or insufficiently diluted product that still contains a toxic substance. For any serious, persistent, urgent, or worsening symptom, and for anything involving pregnancy, infants and children, or mental health, consult a licensed medical provider and do not substitute homeopathy for needed treatment or vaccination. Used with clear eyes and never as a replacement for proven medicine, the direct physical risk is low; the harm is in what it can displace.
Homeopathy is a therapeutic system created by the German physician Samuel Hahnemann in the 1790s, built on two ideas: 'like cures like' (a substance that causes symptoms in a healthy person is used to treat similar symptoms in a sick one) and potentization, the belief that repeated dilution and vigorous shaking make a remedy stronger. The difficulty is that remedies are usually diluted far past the point (around 12C) where any molecule of the starting material could remain, so most are materially water, alcohol, or sugar, with no established mechanism by which they could act. The evidence here is unusually settled. Australia's NHMRC assessed 57 systematic reviews covering 176 studies and found no health condition with reliable evidence of benefit; the UK Parliament and Cochrane reached the same placebo-level verdict. The remedies are usually harmless in themselves, so the real hazards are indirect: delaying or replacing effective treatment, and rejecting vaccines in favor of homeopathic 'nosodes' that do not protect against disease.
A globally popular 200-year-old system whose remedies are diluted past the point of containing any active substance, and which the best evidence finds no better than placebo.
What people take it for
These are the reasons people give for taking it. They are not effects it has been shown to have.
How it is supposed to work
There is no established physical mechanism by which homeopathy could work as claimed. Most homeopathic remedies are diluted beyond Avogadro's number, the point past which it is statistically unlikely that even a single molecule of the original substance remains, so the remedy is, materially, water or a sugar pill. Proposed explanations like "water memory" are not supported by mainstream physics or chemistry. To the extent patients improve, the explanations are the placebo and meaning response (amplified by long, empathetic consultations), natural recovery, and regression to the mean, not the remedy's claimed action.
What people get wrong
Often saidHomeopathy works. There are positive studies and millions of users.
ActuallyAcross the best evidence it is no better than placebo. Australia's NHMRC assessed 57 systematic reviews covering 176 studies and found no condition with reliable evidence of effectiveness; the 2010 UK Parliament review and Cochrane reached the same conclusion. Individual positive trials tend to be small, lower quality, or unreplicated, and improvement is better explained by placebo, natural recovery, and attentive consultations. Popularity is not evidence of effect.
Often saidMore dilution makes a remedy stronger.
ActuallyHomeopathic potentization dilutes past the point where chemistry allows any active molecule to remain. Around a 12C dilution (one part in 10 to the 24th power) the preparation statistically contains no molecule of the original substance, so it is materially water, alcohol, or sugar. No proposed mechanism, including 'water memory,' has scientific support.
Often saidHomeopathy is harmless, so there is no downside to trying it.
ActuallyThe remedies are usually inert, but using homeopathy in place of effective treatment, or rejecting vaccines for homeopathic 'nosodes,' can cause preventable harm. In 2009 the WHO advised against using homeopathy to treat HIV, TB, malaria, influenza, and infant diarrhoea, warning it can displace treatments that work. The danger is in what it replaces, not in the sugar pill itself.
Who profits, and who pushes back
NHMRC & major authorities
Concluded after reviewing 61 conditions that there are no health conditions for which there is reliable evidence that homeopathy is effective.
Systematic reviewers
Found no homeopathic remedy and no condition for which homeopathy is convincingly different from placebo, casting doubt on the core dilution claim.
Homeopathic practitioners
Maintain that potentized remedies and "like cures like" work, citing individualized practice and selected positive trials, within a globally established system.
Public-health & physics perspective
Note that ultra-dilution leaves no active substance and no plausible mechanism, and warn against replacing effective treatment or vaccines with homeopathy.
Where the research comes from
Most of the published research on this comes from one place. 82% of it is from India. Findings that no unrelated group has reproduced are weaker than the study count makes them look.
| Place | Share of published research |
|---|---|
| India | 82% |
| Europe (Germany, France, UK) | 68% |
| Global | 60% |
| Latin America | 55% |
How we got here
Homeopathy begins with Samuel Hahnemann (1755 to 1843), a German physician and translator who, dosing himself with cinchona bark around 1790, concluded that a substance producing a symptom in the healthy could treat that symptom in the sick. He set this out in his 1796 'Essay on a New Principle' and later systematized it in the Organon of the Healing Art (1810). In an era of bloodletting and aggressive purging, his gentle, individualized remedies felt safer and won a large following. Through the 19th century homeopathy spread across Europe and the Americas and took especially deep root in India, where the government formally recognized it in 1973 and folded it into the state AYUSH system; India now has the world's largest body of homeopathic practitioners. As controlled trials accumulated through the 20th and 21st centuries, national reviews in Australia and the United Kingdom concluded there was no reliable effect beyond placebo, even as the practice remained popular worldwide.
- 1796Hahnemann publishes 'Essay on a New Principle,' setting out 'like cures like'
- 1810Hahnemann issues the Organon of the Healing Art, systematizing homeopathy
- 19th c.Spreads across Europe and the Americas and takes deep root in India
- 1973India formally recognizes homeopathy and regulates it (later within AYUSH)
- 2005Shang et al. in The Lancet report effects consistent with placebo; editorial 'The end of homoeopathy'
- 2009WHO advises against using homeopathy to treat HIV, TB, malaria, influenza, and infant diarrhoea
- 2010UK House of Commons Science and Technology Committee finds no better than placebo, urges the NHS to stop funding it
- 2015NHMRC reviews 57 systematic reviews (176 studies): no condition with reliable evidence of benefit
- 2016US FTC requires competent and reliable scientific evidence for OTC homeopathic efficacy claims
How it is understood
Homeopathy is a medical system created by German physician Samuel Hahnemann (1755-1843), reacting against the harsh medicine of his era. It rests on two core principles. The first is "like cures like" (the law of similars): a substance that causes certain symptoms in a healthy person can, in homeopathic form, treat those symptoms in a sick one. The second, and more famous, is potentization: remedies are made by repeatedly diluting a substance and vigorously shaking (succussing) it, with homeopaths holding that this makes the remedy more potent, even when diluted so far that essentially no molecule of the original substance remains. Homeopathy spread worldwide and is especially popular in India and parts of Europe, where it is integrated into some health systems; it is practiced as a complete system, with detailed individualized consultations that many patients find deeply attentive and satisfying. It is included here as a major, globally practiced system, examined honestly.
At a glance
- Founder
- Samuel Hahnemann (1755-1843)
- Principles
- "Like cures like" + ultra-dilution
- Dilution
- Often beyond Avogadro's number (no molecule left)
- Verdict
- No reliable evidence of benefit over placebo
What this entry does not yet cover
What follows is unfinished work on our side, not a finding about Homeopathy. A short entry is not a safe entry.
- Cost and market. We have not documented what it sells for or who sells it.
- Supply chain. We have not mapped where it is made.
- Who uses it. We have not documented the user groups.
- What could change. No forward-looking summary yet.
- How it compares. We have not set it against the alternatives.
- Children and teenagers. We have not checked what is known about younger people.
Sources
NHMRC assessed 57 systematic reviews covering 176 studies and concluded no health condition has reliable evidence homeopathy is effective; should not be used for serious conditions
FTC 2016 enforcement policy: OTC homeopathic efficacy claims require competent and reliable scientific evidence; most rest only on traditional homeopathic theories
US Federal Trade Commission press release, Enforcement Policy Statement on OTC Homeopathic Drugs
FTC policy statement full text: competent and reliable scientific evidence standard and required disclosures for OTC homeopathic drugs
US Federal Register, Enforcement Policy Statement on Marketing Claims for OTC Homeopathic Drugs
UK House of Commons Science and Technology Committee 2010 found homeopathy no better than placebo and recommended the NHS stop funding it
UK Parliament, Science and Technology Committee, Evidence Check 2: Homeopathy (HC 45, 2009-10)
Shang et al. 2005 Lancet meta-analysis: effects consistent with placebo; accompanying editorial 'The end of homoeopathy'
The Lancet, 'Are the clinical effects of homoeopathy placebo effects?' (Shang et al., 2005)
2015 Cochrane review found insufficient good-quality evidence that Oscillococcinum prevents or treats influenza
WHO in 2009 advised against using homeopathy to treat HIV, TB, malaria, influenza, and infant diarrhoea
Sense about Science, 'Homeopathy and the WHO' (WHO department statements, 2009)
Hahnemann (1755-1843) published the 1796 essay setting out like cures like; dilution past ~12C leaves no molecule; summary of NHMRC/UK/Shang/Cochrane verdicts and consensus against the mechanism
India formally recognized and regulated homeopathy in 1973 and hosts the largest body of homeopathic practitioners within AYUSH