How does homeopathy work?

Homeopathy is a system of medicine started in Germany by a doctor named Samuel Hahnemann (1755–1843). It is used by millions of families today, especially in India. To understand it, start with the medicine of his time.

Around 1800, doctors often drained blood (bloodletting), gave strong purges made with mercury, and raised blisters on the skin. These treatments often did more harm than good. Hahnemann was so unhappy that he stopped practising and earned his living translating medical books.

In 1790, while translating a book by the Scottish doctor William Cullen, he doubted Cullen's reason for why cinchona bark treated malaria fever. He took the bark himself and reported fever-like symptoms. From this he came to believe that a substance that causes symptoms in a healthy person can cure similar symptoms in a sick one. He published the idea in 1796, coined the word "homeopathy" (Greek for "similar suffering") by 1807, and set out the full system in his book the Organon in 1810.

Two notes from science. Others who repeated the bark test did not reliably get the same symptoms. And the bark really does fight malaria, because it contains quinine, found in 1820, which kills the malaria parasite in the ordinary way drugs work.

Homeopathy reached India in the 1830s, when the doctor J. M. Honigberger worked at Maharaja Ranjit Singh's court in Lahore, and it grew fast in Bengal. Today it is one of India's official AYUSH systems, with its own degree (BHMS), research council (CCRH) and regulator (NCH), and more than 3.4 lakh registered practitioners. Sister boxes: AyurvedaClear, UnaniClear and MedicineClear.

This chapter explains homeopathy in its own terms, the way its books and teachers describe it. What the scientific evidence says comes later, in chapter 5.

Like cures like (in Latin, similia similibus curentur). Homeopathy teaches that a substance which causes certain symptoms in a healthy person can, in a special diluted form, treat similar symptoms in a sick person. Cutting a red onion makes your eyes and nose stream, so the onion remedy, Allium cepa, is described for colds and hay fever with streaming eyes and nose.

How are these "symptom pictures" found? By provings: healthy volunteers take a substance and write down every change they notice in a diary. The collected symptoms form the materia medica. India's research council, CCRH, still runs proving studies.

Then case-taking. A homeopath asks about much more than the main complaint: sleep, mood, food cravings, what makes things better or worse. The aim is to find the one remedy whose picture best matches the whole person. Two people with the same cold may be given different remedies. Classical homeopathy gives a single remedy at a time, in the minimum dose, prepared by the dilution and shaking you'll see in the next chapter.

A fair note: vaccines are sometimes compared with "like cures like", but they work differently. A vaccine holds a measured amount of a germ's parts that immune cells can detect, and it makes antibodies you can measure (see ImmuneClear).

Homeopathic remedies are made by potentisation. Take 1 drop of the starting liquid, add 99 drops of water or alcohol, and shake hard with firm knocks. That is 1C, a dilution of 1 in 100. Hahnemann knocked the bottle on a leather-bound book; this shaking is called succussion. Repeat: 2C is 1 in 10,000, 6C is 1 in 10¹², 30C is 1 in 10⁶⁰. (The X scale uses 1 in 10 per step, so 24X equals 12C.) Homeopathy teaches that each step makes the remedy stronger.

Chemistry lets us count what is left. A mole of anything holds 6.022 × 10²³ particles (Avogadro's number). Start with a whole mole in a litre, 58 g of table salt, which homeopathy calls Natrum muriaticum. Each C step divides the count by 100. At 12C you expect only 0.6 of a molecule per litre: most bottles have none at all.

The maths for 30C: 6.022 × 10²³ ÷ 10⁶⁰ = 6 × 10⁻³⁷ molecules per litre. To expect one molecule you'd need 1 ÷ (6 × 10⁻³⁷) ≈ 1.7 × 10³⁶ litres. Earth's oceans hold about 1.3 × 10²¹ litres, so that is about 10¹⁵ oceans, a ball of water about 147 million km across, nearly the distance from Earth to the Sun. 200C is 1 in 10⁴⁰⁰, far more than the roughly 10⁸⁰ atoms in the whole visible universe. Hahnemann couldn't have known this: the first estimate of molecule numbers came in 1865, after he died.

So how could a remedy act? Some homeopaths propose water memory: water keeps an imprint of what was dissolved in it. In 1988 Jacques Benveniste's lab reported such an effect in Nature, but when the tests were repeated blind, it vanished, and later labs could not repeat it. Physics adds that the hydrogen bonds holding water molecules together break and re-form about every picosecond (a millionth of a millionth of a second), so there is no lasting structure to store a pattern. Water has also touched countless other substances. Some researchers, including a 2010 IIT Bombay team, reported tiny particles of the starting metal in some high potencies, but this has not been shown to cause any effect in patients.

Most homeopathic remedies start as a mother tincture, marked Ø. Fresh or dried plant material, such as red onion or the flowers of Arnica, is chopped and left to soak in alcohol for days or weeks, then pressed and filtered. India's official standard, the Homoeopathic Pharmacopoeia of India, says how each one is made.

Some starting materials don't dissolve: metals, minerals, oyster shell (Calcarea carbonica). These are triturated: ground with 99 parts of milk sugar (lactose) in a mortar. Hahnemann described about an hour of grinding per step. After three steps the powder can be dissolved and diluted like a liquid (chapter 3).

You rarely swallow the liquid itself. Tiny white globules, made of cane sugar, are wetted with a few drops of the diluted remedy in strong alcohol and left to dry. So a 30C pill is sugar that was moistened with a liquid expected to hold no molecule of the starting substance.

How does a homeopath pick a remedy? With a repertory: a huge index that lists symptoms, called rubrics, and under each the remedies linked to it in provings. J. T. Kent's repertory (1897) is still used, often through software, including programs made in India. The homeopath combines the patient's rubrics to find the remedy that covers most of them. In India, homeopathic medicines are licensed under the Drugs and Cosmetics Act.

People often say, "I took it and I got better." That is real, and it matters. But many illnesses get better on their own, and a caring consultation can make us feel better too (the placebo effect). To know whether a remedy adds anything, we need a fair test.

A fair test compares two groups chosen at random: one gets the remedy, the other an identical-looking dummy pill (a placebo). Ideally it is double-blind: neither patients nor doctors know who got which, so hopes can't tip the result. Only the difference between the groups belongs to the remedy. MedicineClear has a full trial simulator.

There's a sneaky effect too: regression to the mean. People visit a healer on their worst days. Symptoms go up and down, so after a very bad day the next days are usually better, whatever you take.

What the big reviews found. Australia's NHMRC (2015) looked at 176 studies across 61 conditions and found no health condition with reliable evidence that homeopathy works better than placebo. A 2005 Lancet analysis by Shang and colleagues found that the larger, better trials showed effects compatible with placebo. NHS England stopped routinely funding it in 2017. Homeopaths dispute these reviews: they argue that individualised treatment is hard to test this way, and one 2014 review suggested small effects, though from low-quality evidence. India's CCRH runs its own trials and reports positive results; most are small and have not been repeated independently.

Safety. A 30C remedy contains essentially nothing, so the pill itself poses little direct risk. The real dangers are delaying effective treatment for serious illness (the WHO warns against homeopathy for HIV, TB, malaria, flu and infant diarrhoea), and low-dilution or badly made products: in 2017 the US FDA found far too much toxic belladonna in some homeopathic teething tablets.

Many Indian families use homeopathy alongside other kinds of medicine. Whatever you choose, a few rules keep everyone safe. This page explains; it cannot tell you what is right for your own body. For that, see a qualified doctor.

Never stop prescribed medicine on your own, such as insulin, asthma inhalers, epilepsy or blood-pressure medicine. Stopping can be dangerous. Tell every doctor and practitioner everything you take.

For serious illness, go to a qualified doctor quickly: high fever that won't settle (dengue and malaria are common in India), trouble breathing, chest pain, a child who is floppy or not drinking, or a wound that is getting worse. In an emergency call 112 or 108. Delay is the biggest real risk of any alternative treatment.

Vaccines hold measured parts of a germ that train your immune system, and they are tested in huge trials (see ImmuneClear). Homeopathic "prophylaxis" has not been shown to protect like a vaccine, and even the UK Faculty of Homeopathy says it should not replace vaccination. In 2020 India's AYUSH ministry suggested the remedy Arsenicum album 30 against the new coronavirus; there was no trial evidence that it prevents COVID-19. India's protection came from vaccines: more than 220 crore doses. India has also been polio-free since 2014 thanks to vaccination.

So why do people choose homeopathy? Often for good human reasons: a long, unhurried consultation where they feel heard (an average Indian GP visit lasts about 2 minutes), gentle pills with few side effects, low cost, and family tradition. Those are real needs, and good medicine should meet them too. Compare with AyurvedaClear, UnaniClear, SiddhaClear, NaturopathyClear and MedicineClear.