The 'active' ingredient in homeopathy (the bit that is supposed to have some effect) is water. That’s it. Nothing more.
It is rather embarrassing to have to write this, but it has come to my attention that a lot of intelligent people (even students studying science-based degrees) believe homeopathy is a real medicine. It is not. It contains chemicals diluted down so much that there is none of the original chemical left. It is just water. Any suggestions of “water memory” have no grounding theoretically (it does not fit it with anything we know about chemistry) or empirically (there is no evidence water ‘remembers’ the chemicals it was once in contact with). We might rewrite the science if there was some suggestion that homeopathy actually healed people, but there isn't.
There has been plenty of research on homeopathic medicine, and plenty of systematic reviews (where all the separate research is put together and conclusions are made). In 2002, Edzard Ernst (a former homeopathic practitioner!) did a systematic review of the systematic reviews and concluded that there was no convincing evidence for clinical effects beyond placebo. Since then Ernst has published many papers continuing this theme*. He has claimed homeopathy is in “conflict with fundamental rules of medical ethics” and “among the worst examples of faith-based medicine”.
The placebo effect is not to be ignored. If you expect a treatment to improve your condition, often your condition will improve even if that treatment is not a real medicine (often placebos are mere sugar pills). The psychologist Nicholas Humphrey suggests this has evolved as part of a “health management system”. The body has multiple mechanisms to try to cure ailments, which have both costs and benefits. This health management system uses information, including psychological cues, to ‘decide’ which mechanisms to use. The thought that you are receiving treatment which will help you, may lead to the system changing which mechanisms it deploys, and this may lead to some costly mechanisms being reduced. The whole process of homeopathy, including the various nonsense the homeopaths may say during treatment, may cause a placebo effect.
Surely homeopathy is worth it then? It might all be lies, but ignorance is bliss as they say. The people duped by this scam are receiving the placebo effect and getting better, even if at a high price. What’s the problem? Well there are three.
1. The NHS funds homeopathic remedies. Not only are taxes being wasted, but the money that is spent on homeopathy could be spent on much more effective treatments.
2. People often see doctors as cold and clinical, and drugs as dangerous. Homeopathic remedies lack side-effects and are seen as “alternative”. This creates the illusion that homeopathic is somehow better than real medicine. This, along with the common occurrence of homeopaths advising patients not to use conventional treatments, leads to people rejecting real medicine, and therefore missing out on proper treatment.
3. It adds to the creeping view in society that evidence-based science is over-rated or useless, and that faith is somehow more desirable. No it isn’t. Faith barely ever comes true. The only good way of discovering the truth is to rigorously review and criticise the evidence available. It’s a complete disgrace that hundreds of years of good science and philosophy are being ruined by the idea that if you want something to be true, then it’ll be true. Sorry, but that isn’t how the world works. Get over it.
People can pay for homeopathy with their own money if they want, but while it is paid for by the NHS, homeopathy kills.