Homeopathy is a medical system developed by Samuel Hahnemann in Germany in the late 18th century, based on two principles: (1) "Like cures like" (similia similibus curentur) — a substance causing symptoms in a healthy person can cure similar symptoms in a sick person; and (2) the "law of infinitesimals" — extreme dilution increases therapeutic potency ("potentisation"). Preparations are made by serial dilution (1:100 at each step) with vigorous shaking (succussion) between dilutions, resulting in potencies like 30C (10⁻⁶⁰ dilution) where no molecule of the original substance statistically remains. Homeopathy is used by an estimated 200-300 million people globally, with strong traditions in France, Germany, India and Latin America.

What does the scientific evidence show?

The most comprehensive evidence synthesis: the Australian NHMRC 2015 systematic review of 1,800 studies across 57 systematic reviews covering 68 health conditions concluded: "There was no good-quality evidence to support the claim that homeopathy is effective in treating health conditions." When studies of sufficient quality are examined: effect sizes consistent with placebo response — diminishing as study quality increases. This is the characteristic pattern of an ineffective treatment: it appears to work in poor-quality studies (where bias inflates results) and disappears as study quality improves. Multiple independent Cochrane reviews reach the same conclusion for specific conditions (homeopathy for attention deficit, asthma, flu, headache, menopausal symptoms — no reliable evidence).

Can water really have memory?

No — this has been comprehensively refuted. The water memory hypothesis was proposed by Jacques Benveniste in 1988 to explain how homeopathic dilutions could have biological effects without any molecules present. Three conditions for water memory would be required: (1) water molecules form structured clusters ("clathrates") that persist; (2) these structures encode specific biological information; (3) this information is transferred therapeutically. Physical chemistry: water molecules exchange hydrogen bonds in picoseconds (~10⁻¹² seconds) — far too rapidly to store structural information. Nuclear magnetic resonance (NMR) spectroscopy: water samples prepared as homeopathic dilutions are indistinguishable from plain water. Benveniste's own results could not be reproduced under blinded conditions. No physical mechanism for water memory is consistent with known chemistry or physics.

Is homeopathy harmful?

The homeopathic preparation itself causes no pharmacological harm — there are no active molecules to cause toxicity. However, indirect harm is well-documented: (1) Opportunity cost and delayed treatment: using homeopathy for conditions requiring effective medical treatment (meningitis, malaria, HIV) has caused preventable deaths, documented by WHO and case reports globally. (2) Vaccine alternatives: homeopathic "nosodes" are marketed in some countries as alternatives to vaccination against rabies, malaria, flu and COVID-19 — with no immunological protective mechanism. (3) Anti-vaccination advice: some homeopathic practitioners advise against vaccination. (4) Financial harm: consultations and preparations can be expensive, particularly for chronic conditions. The harm from homeopathy comes not from the dilution but from what it displaces.

Why do people report that homeopathy "worked"?

Several genuine explanations exist for positive experiences: Natural recovery (most illnesses are self-limiting — anything tried during recovery gets credited); placebo response (approximately 30-35% objective improvement in subjective symptoms from inert treatments, when administered with attention and therapeutic optimism); regression to the mean (people seek treatment when symptoms are worst — improvement to average may occur regardless of treatment); the therapeutic encounter (60-minute, highly attentive consultation vs typical 10-minute GP appointment creates genuine psychological benefit that is not the same as the homeopathic remedy working pharmacologically). These are real effects — but they are the effects of the encounter, the expectation, the natural history and the time — not the ultra-dilute preparation.

How does GMJ News cover homeopathy?

GMJ News covers: the Avogadro number impossibility of molecular effect at 12C+; Hahnemann's founding principles in historical context; the Benveniste water memory affair and refutation; NHMRC 2015 comprehensive systematic review; WHO's explicit discouragement for serious infectious disease; NHS England's 2017 funding removal; indirect harm (opportunity cost, nosodes, vaccine avoidance); and the legitimate unmet need (attentive consultations) that homeopathy appears to serve. GMJ is scientifically rigorous but empathetic: the chemistry is unambiguous, the evidence is clear, and people who use homeopathy deserve honest information — not dismissal.

Home › Topics › Homeopathy — A Scientific Assessment

Homeopathy — A Scientific Assessment

GMJ News knowledge hub · last reviewed September 2026 · Georgian Medical Journal

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Homeopathy — the medical system founded by Samuel Hahnemann in the 1790s based on the principles of “like cures like” (similia similibus curentur) and extreme serial dilution (30C = 10-60 dilution — far beyond Avogadro’s number of 6×1023, meaning no molecule of original substance statistically remains in the preparation) — is among the most extensively scientifically investigated complementary practices, with the 2015 Australian National Health and Medical Research Council (NHMRC) systematic review of over 1,800 studies — the most comprehensive evidence synthesis ever conducted on homeopathy — concluding that there is no good-quality evidence that homeopathy is more effective than placebo for any health condition (WHO). The WHO explicitly states that homeopathy “should not be used to treat health conditions that are chronic, severe, or life-threatening” — and strongly discourages its use for serious infectious diseases including HIV/AIDS, tuberculosis, malaria and infant diarrhoea.

Key messages

30C dilution = 10⁻⁶⁰ — no molecules of original substance remain

Avogadro's number is approximately 6×10²³ (the number of molecules in one mole of substance). At a 12C homeopathic dilution (10⁻²⁴), the probability of finding a single molecule of the original substance is statistically negligible. Common remedies use 30C (10⁻⁶⁰) or 200C (10⁻⁴⁰⁰) dilutions — concentrations where the original substance has been mathematically diluted out of existence many times over. This is not a matter of scientific debate — it is physical chemistry.

Australia NHMRC 2015 — the most comprehensive evidence review

The Australian National Health and Medical Research Council conducted the most comprehensive systematic review of homeopathy ever performed: 57 systematic reviews covering 68 health conditions from 1,800 studies. Conclusion: "There was no good-quality evidence to support the claim that homeopathy is effective in treating health conditions." No condition showed homeopathy reliably superior to placebo in high-quality studies. The evidence base, as a whole, does not support homeopathy as a treatment for any health condition.

Water memory — comprehensively refuted

Jacques Benveniste (Nature, 1988) claimed that water retains a biological "memory" of antibody solutions even after extreme dilution — the only physical mechanism that could explain homeopathic effect. Nature published it with an unprecedented editor's note requiring replication by independent observers. Three independent replication attempts — supervised by Nature editors — failed to reproduce the result under blinded conditions. Water memory has no support from physics, chemistry or verified replication.

WHO explicitly discourages homeopathy for serious disease

WHO position (Dr Margaret Chan, Director-General): homeopathy "should not be used to treat health conditions that are chronic, severe, or life-threatening." WHO explicitly discourages use of homeopathy for: HIV/AIDS; tuberculosis; malaria; infant diarrhoea; influenza. In 2009, WHO convened a meeting specifically on the misuse of homeopathy in these conditions — documenting cases of serious harm from replacing effective treatment with homeopathic preparations.

The therapeutic encounter — why people feel better

Homeopathic consultations tend to be significantly longer than conventional GP appointments (up to 60 minutes), highly patient-centred, empathetic and individualised. This therapeutic encounter itself — regardless of the diluted preparation — activates placebo and non-specific effects: reduced anxiety, enhanced self-efficacy, parasympathetic activation. The remedy has no pharmacological effect; the encounter may have significant psychological benefit. Understanding this distinction is important: the encounter can be maintained without the misleading therapeutic claim.

NHS England stopped funding in 2017

NHS England announced in 2017 that GPs in England should not prescribe homeopathy, and NHS funding ceased. The British Medical Association had declared homeopathy "witchcraft" and opposed NHS funding for decades. The decision was based on: lack of evidence; opportunity cost (limited NHS resources better spent on evidence-based treatments); failure to meet evidence standards required for NHS-funded interventions. Some NHS clinical commissioning groups had already stopped funding earlier.

Key statistics

10⁻⁶⁰

30C homeopathic dilution — far beyond Avogadro's number (6×10²³)

Physical chemistry

1,800 studies

reviewed by NHMRC 2015 — no good evidence that homeopathy works for any condition

NHMRC Australia 2015

200M+ users

estimated global homeopathy users — significant cultural and traditional use

WHO

2017

year NHS England stopped funding homeopathy prescriptions

NHS England 2017

WHO discourages

homeopathy for HIV, TB, malaria, infant diarrhoea, influenza (Dr Chan, WHO DG)

WHO 2009/2019

1796

year Samuel Hahnemann published first homeopathic principles (Organon)

History

Homeopathy evidence quality by condition — NHMRC 2015 review assessment

Source: NHMRC Australia 2015. No condition showed reliable benefit over placebo in high-quality studies.

Glossary of key terms

Hahnemann's founding principles
History/PhilosophySamuel Hahnemann (1755-1843), German physician, developed homeopathy in the 1790s. Principle 1 — Similia similibus curentur ("like cures like"): a substance that causes symptoms in a healthy person can cure similar symptoms in a sick person (tested on himself — quinine caused fever-like symptoms, which he interpreted as its mechanism for treating malaria). Principle 2 — Law of infinitesimals: extreme dilution increases potency ("potentisation") — each dilution step must be accompanied by vigorous shaking (succussion). These principles had intuitive appeal before germ theory and modern pharmacology. Hahnemann was genuinely trying to find gentler treatments than the harsh medicine of his era (bloodletting, mercury purges).

Potency notation
ChemistryHomeopathic potency notation: X (or D) = 10-fold dilution at each step; C = 100-fold dilution at each step. 6C = diluted 100-fold six times = 10⁻¹² (one part in a trillion). 12C = 10⁻²⁴ (approaching Avogadro's number). 30C = 10⁻⁶⁰ (used in most remedies — far beyond Avogadro). 200C = 10⁻⁴⁰⁰ (used in "high potency" remedies). To put 30C in perspective: if the observable universe were filled with water and you added one molecule of a substance, the resulting concentration would be approximately 10⁻⁸⁰ — and 30C is still less concentrated than that.

The Benveniste affair (water memory)
Nature 1988Jacques Benveniste (INSERM, France) published in Nature (1988) a paper claiming that human basophils degranulated in response to anti-IgE antibodies even when diluted beyond Avogadro's number — claiming water retained biological "memory." Nature took the unprecedented step of publishing it with an editorial note: results "are not convincing but are offered for international consideration." Nature sent a team to replicate: James Randi (magician/sceptic), Walter Stewart (NIH fraud investigator), and others observed blinded experiments at Benveniste's laboratory. Results: the effect disappeared under double-blind conditions; Benveniste's team could not replicate their own results when blinded. The paper has never been successfully replicated under rigorous blind conditions.

Indirect harm from homeopathy
WHO/EvidenceDirect harm from the homeopathic preparation itself (the dilution) is negligible — there are no pharmacologically active molecules to cause harm. Indirect harm: (1) Opportunity cost: using homeopathy instead of effective treatment for a serious condition (malaria, HIV, cancer, infant meningitis). (2) Delaying effective treatment: time spent pursuing homeopathy while a condition worsens. (3) Nosodes as vaccine alternatives: homeopathic preparations claimed to protect against infectious diseases, causing vaccine avoidance. (4) Anti-vaccination advice: some homeopaths actively advise against vaccination. (5) Financial cost: consultations and preparations, particularly for chronic conditions. These harms have been documented in case reports and systematic literature reviews.

How homeopathy remains legally marketed
RegulatoryHow can products with no evidence of efficacy remain legally marketed? Regulatory exemptions: In the EU, homeopathic products can be registered without proof of efficacy under a simplified registration process (EU Directive 2001/83/EC Art. 14-16) — with only labelling restrictions (no therapeutic claims on the label). In the USA, homeopathic products have been FDA-exempt since 1938 (when the FDA Act was written, the head of the Senate Health Committee was a homeopathic physician and secured a permanent exemption). The FDA has been attempting since 2018 to apply risk-based oversight to homeopathic products. Historical regulatory exemptions — not scientific evidence — explain why homeopathy is still sold in pharmacies.

Why do people use homeopathy?
Social science/ResearchSocial science research reveals multiple reasons: longer, more empathetic, more individualised consultations; the remedy itself feels personalised (different remedies for different symptom patterns); relief from seeing a practitioner who "listens" — compared to a 10-minute GP appointment; cultural tradition (strong in Germany, France, India); reaction against pharmaceutical medicine (concerns about side effects); previous positive experiences (which may have been spontaneous remission, natural history, or placebo response). Understanding these drivers is more useful than dismissing homeopathy users as irrational — and suggests addressing the unmet need for attentive, holistic primary care.

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Homeopathy — A Scientific Assessment

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