Homeopathy (also spelled homœopathy or homoeopathy), from the Greek words homoios (similar) and pathos (suffering), is a controversial system of alternative medicine, best known for its use of remedies without chemically active ingredients. The theory of homeopathy was developed by the Saxon physician Samuel Hahnemann (1755–1843) and first published in 1796. It has a wide and growing popularity in areas where it is practiced today, but neither its empirical nor its theoretical foundation is accepted by any major scientific or medical organizations. Homeopathy essentially treats "like with like". The patient describes his or her symptoms in detail, with equal emphasis placed on both physical and psychological symptoms. The practitioner then prescribes very small, nontoxic doses of a selected substance.
- 1 Basic principles
- 2 The practice of homeopathy
- 3 The appeal of homeopathy
- 4 The skeptical view of homeopathy
- 5 The applicability of traditional scientific procedures
- 6 Some specific controlled studies and clinical trials
- 7 Misconceptions about homeopathy
- 8 External links
Theory of disease
The conventional theory of disease in Hahnemann's time was based on the four humours. Mainstream medicine in those days focused on restoring the balance in the humours and thus the vital force by either removing an excess of a particular humour (through such things as bloodletting and purging, the use of laxatives, enemas and obnoxious substances that made patients vomit) or by suppressing symptoms associated with the humour(s) causing troubles, for instance giving patients substances associated with cold and dry if the patient was hot and wet (e.g. feverish).
The late 18th century was a time of intense exploration, and many new diseases were being identified. The model of internal humors was proving to be inadequate. For example, many new diseases were clearly associated with certain geographic locations, which was difficult to explain through totally internal mechanisms like humours. Instead, more scientists were considering a model of external causes. One variation was the idea of independent outside agents in the air, known as miasms or simply "bad airs". For example, malaria was thought to be caused by the bad airs found in southern swamps and jungles, explaining why it struck down people travelling in those areas.
Hahnemann's idea was that by suppressing or going against the humours, doctors were sabotaging the body's own efforts to heal itself. He considered symptoms to be the way the body fought disease; for example, fever was its attempt to make itself warmer to fight whatever was ailing it. Unlike the humour-based logic, which would attempt to cool the feverish patient, Hahnemann felt that if the body wanted to be warm, making it warmer would be the proper solution. From this he developed the expression of the "like-cures-like" principle.
Scientific medicine has discarded both the theory of the four humours and the theory of miasms (and similar ideas of that time), in favour of the germ theory of disease as part of a physiological model, based on the work of scientists like Louis Pasteur, Alexander Fleming, and Joseph Lister.
Beginning with his early work, Hahnemann rejected the prevailing physical model, in favour of seeing disease as more dynamic (spirit-like). He considered the spiritual factors as the root cause of all disease, what he termed the "highest disease." Most later homeopaths, in particular James Tyler Kent, have tended to put even more emphasis on spiritual factors.
Vitalism was more or less a part of mainstream science through the 18th century. Whereas modern medicine sees bacteria and viruses as the causes of many diseases, some modern homeopaths regard them as effects, not causes, of disease. Others have to some extent adapted to the views of modern medicine by referring to disturbances in and stimulation of the immune system, rather than the vital force.
In accordance with this view of disease, classical homeopathic treatment requires an interview, known as "anamnesis", which may take an hour or more, to determine the totality of the patient's symptoms. Hahnemann stated that a person could have more than one disease at a time, each of which might be contibuting to the symptom picture of the patient. Hahnemann's approach was that the practitioner should first seek to treat the constant nature diseases, as these can more readily be identified in most cases (by cause, e.g. Arnica for contusion disease) and since they are fixed in nature, they are always treated with the same medicine, thus simplyfying treatment. The homeopathic approach to the remaining pathic diseases could then more easily be used.
Although modern homeopaths sometimes suggest that their art is especially effective against chronic diseases, Hahnemann himself recognized that homeopathy, like conventional medicine, has more difficulty with these than with acute sicknesses. In response, he developed his theory of miasms, which are supposed to cause all chronic disease (apart from that due to orthodox medicine or to faulty living habits). Hahnemann identified three types of miasm: syphilitic, sycotic, and psoric. Some later homeopaths have extended this list. Constantine Hering developed the psora doctrine by propounding that symptoms develope in a particular way:
- from less vital to more vital organs
- from the surface to the interior
- from the extremities to the upper part of the body
As the patient is cured, the symptoms are said to be relieved (or to temporarily reappear) in the opposite order.
The law of similars
The first and most important "natural law" expressed by Hahnemann, the one from which homeopathy derives its name, is similia similibus curentur—let like cure like. This means that the appropriate substance to treat a disease is one which induces similar symptoms in a healthy person. Homeopathy uses a wide variety of animal, plant, and inorganic substances, from sodium chloride (a.k.a. table salt) to lachesis muta (the venom of the bushmaster snake).
What symptoms are associated with various substances is determined by provings, in which the researcher imbibes the remedy and records all physical, mental, emotional and modal symptoms experienced. A homeopathic repertory is a listing of remedies by symptom, used to determine the most appropriate remedy for a given case. Hahnemann's finding are recorded in Materia Medica Pura. Kent's Repertory (published 1905) lists about 700 remedies. Today, nearly 3000 remedies are used in homeopathy, of which approximately 150 are considered common.
Homeopaths after Hahnemann developed some related but distinct principles for prescribing remedies. One of these is the use of nosodes, which are homeopathic dilutions of the agent or the product of the disease in question. Rabies nosode, for example, is made by potentizing the saliva of a rabid dog. Another principle, used especially in treating chronic disease, is constitutional prescribing in which the homeopath identifies the patient's "constitution" and gives the relevant remedy, which is thought to bring about a cure more or less regardless of the actual symptoms the patient is complaining of.
If symptoms become worse after starting a homeopathic treatment, homeopaths speak of an aggravation or healing crisis. This is considered to be a healing reaction of the body and a sign that the medication is taking effect. In some cases an aggravation does not occur but the symptoms improve immediately or after some time. It is also possible that the symptoms change or old symptoms reappear. The idea of aggravation can be considered a consequence of the law of similars in that the medication initially adds to the symptoms of the disease and only gradually replaces it. Alternatively, the symptoms may be considered a response to the disease by the immune system, which is stimulated by the medication to overcome the disease.
See also: List of common homeopathic remedies
The theory of infinitesimals
The most characteristic—and controversial—principle of homeopathy is that the potency of a remedy can be enhanced (and side effects diminished) by dilution in a particular procedure known as dynamization or potentization. Liquids are successively diluted (with water or occasionally alcohol) and shaken by 10 hard strikes against an elastic body, a process called succussion. Insoluble solids are diluted by grinding them with lactose, a process known as trituration. Homeopathic practitioners believe the vigorous agitation following each dilution transfers some of the "essential property" of the substance to the water, which fits in with the concept of disease as a disturbance in the "vital force" of the patient. The dilution factor at each stage is traditionally 1:10 (D or X potencies) or 1:100 (C potencies). Hahnemann advocated the use of 30C dilutions for most purposes, i.e. dilution by a factor of 10030 = 1060. Some later homeopaths, in particular Kent, have advocated the use of much higher potencies, which can no longer be practically achieved by the traditional method, but require succussion without dilution (Jenichen), much higher dilution factors (LM potencies dilute by 1:50,000 at each stage), or machines which in some way integrate dilution and succussion into a continuous process (Kent). Higher dilutions are generally considered stronger. This is in contrast to conventional medicine and biochemistry, which hold that the effects of a substance are always due to its physical and biochemical activity in the patient's body, and therefore that generally the more of an active ingredient is present in a drug, the more effect (whether positive, negative, or both) it will have.
The choice of potency will depend on a number of factors depending on the homeopath. These can range from how deep seated the disease seems to be to how the patient has reacted to previous remedies. As a general (although not exclusive) rule, European homeopaths will use lower potencies than their American counterparts. Some homeopaths believe that, while lower dilutions may have more of a physiological effect, higher dilutions may have a greater effect on the mental or emotional plane.
The practice of homeopathy
Hahnemann began developing the homeopathic method after coming upon the idea that "like cures like" while translating a work on malaria. Upon reaching a passage stating that quinine was an effective treatment because it was bitter and astringent, Hahnemann felt this implausible because there were many other substances that were equally bitter yet lacked any therapeutic value. To better understand the effects of quinine, he decided to take it himself and observed that his reactions were similar to the symptoms of the disease it was used to treat. This was the birth of the homeopathic principle and is known as "The First Proving".
Hahnemann and his students approached their treatments in a holistic way, meaning that the whole of the body and spirit becomes the focus of therapy, not just the localised disease. Hahnemann himself spent extended periods of time with his patients, asking them questions that dealt not only with their particular symptoms or illness, but also with the details of their daily lives. It is also suggested that the gentle approach of homeopathy was a reaction to the violent forms of heroic medicine common at the time, which included techniques such as bleeding as a matter of course.
Homeopathy was brought to America in 1825 and rapidly gained in popularity, partly due to the fact that the excesses of conventional medicine were especially extreme there, and partly due to the efforts of Constantine Hering. Hering developed the psora doctrine by propounding that symptoms always move in a particular way: from the surface to the interior, from the extremities to the upper part of the body, and from less vital to more vital organs. His "Laws of Cure" state that the cure must take place in the reverse order of the appearance of the symptoms (first in, last out). Homeopathy reached its peak of popularity in America in the decades 1865–1885 and thereafter declined due to a combination of the recognition by the establishment of the dangers of large doses of drugs and bleeding and dissent between different schools of homeopathy.
Nearly as important as Hahnemann himself to the development and popularization of homeopathy was the American physician James Tyler Kent (1849 – 1921). His most important contribution may be his repertory, which is still widely used today. Kent's approach to homeopathy was decidedly authoritarian and unscientific, emphasizing the metaphysical aspects of Hahnemann's teachings, in particular
- insistence on the doctrines of miasm and vitalism,
- rejection of modern scientific and pathological knowledge as a guide to prescribing,
- emphasis on psychological symptoms in prescribing, and
- insistence on the use of very high potencies.
Kent's influence in America was somewhat limited, but his ideas were reimported into Great Britain, where they became the homeopathic orthodoxy by the end of the First World War.
Today, homeopathy enjoys more official recognition in Great Britain than in any other country, largely due to a tradition of royal patronage. The only other countries that come close in this respect are India and Pakistan. In the United Kingdom, as in most countries, homeopathic remedies may be sold over the counter.
In the United States, homeopathic remedies are, like all healthcare products, subject to regulation by the Food and Drug Administration. However, the FDA accords homeopathic remedies a treatment significantly different from that accorded to other drugs. Homeopathic products are not required to be approved by the FDA prior to sale, not required to be proven either safe or effective prior to being sold, not required to be labeled with an expiration date, and not required to undergo finished product testing to verify contents and strength. Homeopathic remedies have their own imprints that, unlike conventional drugs, do not have to identify their active ingredients on the grounds that they have few or no active ingredients. In the United States only homeopathic medicines that claim to treat self-limiting conditions may be sold over the counter, while homeopathic medicines that claim to treat a serious disease can be sold only by prescription. Neither the American Medical Association nor the American Academy of Pediatrics has an official policy for or against homeopathy.
Homeopathy's popularity in the United States is growing. The 1995 retail sales of homeopathic medicines in the United States were estimated at $201 million and growing at a rate of 20 percent a year, according to the American Homeopathic Pharmaceutical Association. The number of homeopathic practitioners in the United States has increased from fewer than 200 in the 1970s to approximately 3,000 in 1996.
Since January 1, 2004 in Germany homeopathic medications, albeit with some exceptions, are no longer covered by health insurance. Since 2001 homeopathy is regulated in the European Union by Directive 2001/83/EC. The latest amendments to this directive make it compulsory for all member states to implement a special registration procedure for homeopathic drugs.
In Mexico the Instituto Politécnico Nacional (IPN) has a school of Homeopaty since 1936. This school has both bachelor and master degrees.
Over twelve thousand medical doctors and licensed health care practitioners administer homeopathic treatment in Britain, France, and Germany. An estimated 500 million people worldwide receive homeopathic treatment.
There is, and always has been, considerable diversity in the theory and practice of homeopathy. The major distinction may be between what can be called the pragmatic and the mystical approach, but it should be remembered that there are not two distinct groups, but a spectrum of attitudes and practices. An early advocate of pragmatism was Richard Hughes, while the most influential mystic was James Tyler Kent. The pragmatists tend to be open to "whatever works", whereas the mystics tend to rely on the research of one or more authorities. There is still considerable diversity in both camps because the pragmatists usually define "working" based on personal experience and the mystics use various sources as authorities. The pragmatists tend to see homeopathy as complementary medicine and are more willing to co-exist with conventional doctors. Many in fact are conventional doctors. The mystics, some of whom are also conventional doctors, see homeopathy as alternative medicine and have more confidence that homeopathy can be used effectively against all diseases, with the caveat that many potential remedies have not yet been proven. The pragmatists are more likely to be interested in proving homeopathy in the framework of mainstream science. They will talk about the "memory of water" and stimulation of the immune system. The mystics see less need to justify their methods with conventional criteria. For them, homeopathy acts on a vital force that is, so far, not accessible to science. The pragmatists are more likely to prescribe (relatively) low dilutions in multiple doses, and sometimes use more than one remedy at a time. The mystics often use higher dilutions, but generally prefer a single remedy and sometimes a single dose. In the extreme form, pragmatists will even accept over-the-counter homeopathic remedies, but the mystics will always insist on an individual prescription. The mystics may see themselves as "classical" homeopaths, although the historical accuracy of the term may be questionable. The pragmatists see themselves as "scientific", even though they are not accepted by the scientific establishment.
See also: List of important homeopaths
The appeal of homeopathy
Homeopathy is popular among patients and practitioners for several reasons. The most important is that they perceive it to be effective. They have personally experienced and heard from friends, colleagues, and the press of many cases, some of them spectacular, in which a sickness was healed after a homeopathic treatment. Their favorable judgement is reinforced by reports of scientific studies reporting positive results. They may be aware that science has found no adequate explanation for the mechanism of homeopathy, but that does not trouble them: "Whoever heals is right".
Disaffection with the establishment
Another reason that many people embrace homeopathy is that they reject the medical establishment, which is perceived to place too much emphasis on machines and chemicals and to treat the disease, not the person. Homeopathic practitioners do, in fact, often spend much more time dealing with their patients than do conventional practitioners. Furthermore, homeopathic preparations have few if any side effects and are generally much cheaper than conventional medications.
The skeptical view of homeopathy
Lack of a mechanism
Many scientific skeptics consider homeopathy to be a pseudoscientific remnant from the age of alchemy. Others consider the belief in homeopathy to be a form of magical thinking.  In fact homeopathy was developed at a time when many of the most important concepts of modern chemistry and biology, such as molecules and germs, were understood poorly or not at all. While proponents may consider the mechanism of homeopathy to be an interesting side issue, skeptics consider the lack of any plausible mechanism to be a serious problem, raising the bar on the quality of evidence required before accepting the existence of the phenomenon under the motto "Extraordinary claims require extraordinary proof".
In Hahnemann's day, many chemists believed that matter was infinitely divisible, so that it was meaningful to talk about dilution to any degree. Although the hypothesis of atoms can be traced back to the ancient Greeks, their actual size was not calculated until 1865 (by Loschmidt). It is now known that there are 6.02×1023 particles in a mole (unit) (Avogadro's number), so that homeopathic dilutions greater than about 24X or 12C are virtually certain to contain not even a single molecule of the initial substance. This fact is recognized by advocates of homeopathy, who assert that the essential healing power of their preparations is not found in the chemical action of molecules, but perhaps in the arrangement of the water molecules, giving rise to the expression "the memory of water". This concept is closely related to the belief in a "vital force", which was common in Hahnemann's day, but was slowly given up by the scientific community as more and more life processes came to be describable in purely materialistic terms, and as the medical model of disease came to be more and more focused on the failure of particular organs and processes in the body. This process began with the synthesis of urea by Friedrich Wöhler in 1828. The consensus among modern scientists is all of chemistry and biology can ultimately be explained in principle by the basic interactions of molecules, even if many processes are far too complex to be understood at this time. In short, the skeptic sees no evidence of a plausible mechanism by which homeopathic dilutions can possibly act.
Closely related to the question of the mechanism is, in the eyes of critics, logical inconsistencies in the theory. The theory assumes that water is imprinted by the properties of molecules that it once came in contact with, even when the molecules are diluted away. If this were so, then where did the pure water used in this process come from? The water that homeopaths themselves use was once in contact with other chemicals, including chemical wastes, radioactive metals, dinosaur urine, and various poisons. According to this skeptical interpretation of homeopathic theory, all water in the world should remember its contact with millions of chemical substances and not just the properties of the chemicals that the homeopath claims will be useful. The answer of the homeopaths, that dynamization involves succussion as well as dilution, is not satisfying, first because it seems improbable that one can amplify order in a solution by shaking it, secondly because a lot of shaking goes on in the natural world as well. Why does a waterfall not dynamize the substances dissolved in the stream? It is not possible to prove that no consistent theory of potentization exists, but none is obvious and advocates have not been able to produce one.
Homeopaths occasionally invoke the unusual properties of water to explain the memory effect. In addition to the problems above, a theory of homeopathy would also have to explain why dynamization works not only with water but also with alcohol and lactose, which have very different properties.
Even if a homeopathic preparation somehow preserves information from the original substances, there is absolutely no plausible mechanism by which that should effect a cure.
Lack of evidence for therapeutic efficacy
Proponents and opponents of homeopathy disagree over whether scientific randomized controlled trials with the use of placebos have shown success with homeopathic methods. Some clinical trials have produced results supporting homeopathy, but critics contend that these trials are flawed. In 1997, The Lancet published a meta-analysis of 89 clinical trials, resulting in an ambiguous conclusion that served as fodder for both supporters and critics of homeopathy.
Skeptics point out that there are very few studies that meet the highest standards of scientific research, and there is a tendency for the better studies to show less effect. Many high quality studies have been published that showed no effect. The few high quality studies that show a positive effect could be the result of statistical fluctuations, that is, if many studies are made, some will by chance appear to support homeopathy. The situation is aggravated by publishing bias—A positive result will probably be published but a negative result is more likely to be suppressed by the initiators of the study, or not written up by the researchers, or rejected by the referees or editors of the journals.
The skeptics tend to reject the evidence of any study that is not double-blind, randomized, and placebo-controlled, since it has been shown many times that the results can otherwise be biased by the placebo effect, or through post hoc reasoning applied to the regressive fallacy.
Skeptic James Randi has offered an award of one million dollars (U.S.) to anyone who can prove the existence of anything supernatural or paranormal. The million dollars is also available to anyone who can, by any means of their choosing, tell the difference between plain water and any homeopathic remedy of their choosing. A recent attempt to win the prize was aired on the BBC science program Horizon. This test, like all others to date, failed.
Having concluded that the controlled studies of homeopathy are too weak to be convincing, the skeptics must still address the widespread reports of successful treatments. They begin by pointing out that anecdotal evidence of controversial phenomena is nearly useless as scientific evidence. Without control cases, it is impossible to distinguish between efficacy of a treatment and spontaneous remission. Without double blinding it is impossible to rule out observer bias and the placebo effect. Without reproduction in a separate study, it is difficult to rule out chance, fraud, or poorly understood systematic effects.
Homeopathy not completely harmless
The skeptical point of view is that homeopathic dilutions have no direct effect at all, so logically they also have no harmful side effects. Some medications labeled as homeopathic, however, are not actually highly diluted and may contain ingredients in dangerous amounts. Either way, patients who rely fully on homeopathic techniques, denying any conventional medicine, are at risk of leaving some easily treatable diseases (such as some early skin cancers) until they become untreatable.
The applicability of traditional scientific procedures
While skeptics tend to reject borderline results from scientific studies because they are, due to the lack of a plausible mechanism, predisposed to believing that there can be no effect, proponents of homeopathy tend to accept these results due to the opposite predisposition based on their personal experience. In addition, they criticize an unwillingness of the establishment to invest the resources needed to test their hypothesis more thoroughly and what they see as weaknesses in the traditional methodologies.
It is often said that homeopathy cannot be tested in objective studies because it is a principle that each patient and each illness be treated individually and an emotional doctor-patient bond is necessary for successful treatment. Aside from the fact that homeopathy is often not practiced this way, with many patients taking over-the-counter preparations according to the recommendations on the label, this objection has no sound basis. While it may be difficult to objectively study some aspects of homeopathic treatment, e.g., the role played by the relationship between pratitioner and patient, the efficacy of homeopathic preparations in high dilution is easily studied. One could, for example, let a practitioner prescribe whatever he wants for whatever patients come to him, and then give half the patients authentic homeopathic preparations and the other half plain water, alcohol or sugar. If the two groups cannot be distinguished at a statistically significant level on the basis of the judgement of the practitioner, the reports of the patients, or objective medical tests, then the hypothesis of efficacy can be rejected.
Rather than insist that all studies be double-blind and randomized, some proponents of homeopathy downplay the importance of the placebo effect by pointing to reports of successful treatment of infants and animals. Scientists answer that even in these cases double-blinding is necessary because (1) the rate of spontaneous remission must be determined, (2) the person evaluating the healing can be influenced by knowing which subjects received the active treatment, and (3) the subjects can respond to the expectations of the person administering the treatment.
Some specific controlled studies and clinical trials
three professors of medicine from the Netherlands, none of them homeopaths, performed a meta-analysis of twenty-five years of clinical studies using homeopathic medicines and published their results in the journal British Medical Journal. This meta-analysis covered 107 controlled trials, of which 81 showed that homeopathic medicines were effective, 24 showed they were ineffective, and 2 were inconclusive. The professors concluded, “The amount of positive results came as a surprise to us.”
However the authors also concluded:
(the results are) not sufficient to draw definitive conclusions because most trials are of low methodological quality and because of the unknown role of publication bias.
Ullman, in fact, argues that studies have confirmed that homeopathic remedies are effective even without personalized treatment in a practitioner-patient relationship. He cites two studies, including one published in the March, 1989 issue of British Journal of Clinical Pharmacology (“A Controlled Evaluation of a Homeopathic Preparation for the Treatment of Influenza-like Syndrome”), to bolster this position. So-called “combination remedies”, in which several homeopathic preparations are combined, are often sold over-the-counter in the United States, and traditional homeopathic theory tends to frown on this approach, but Ullman cites trials that suggest otherwise.
Ullman argues “to ignore the body of experimental data that presently exist on homeopathic medicines and to deny the body of clinical experience of homeopaths and homeopathic patients, one would have to be virtually blind. One can only assume that this blindness is a temporary affliction, one that will soon be cured.”
In 1988, a French scientist Jacques Benveniste working at that country's prestigious INSERM institute claimed to have found that high dilutions of substances in water left a “memory”, providing in vitro evidence corresponding to homeopathy's therapeutic use of infinitesimals. The results from INSERM, supported by work at five different laboratories in four countries, were published in Nature magazine, a highly regarded science journal, but with the caveat that the findings were implausible, and that the work was financed by a large homeopathic drug manufacturer. An attempt by Benveniste to reproduce his own results, carefully scrutinized by a team from Nature, was unsuccessful, ultimately leading to the suspension of Benveniste. Later studies by a consortium of four independant laboratories, led by professor Madelene Ennis, supported his findings. In turn, BBC's Horizon failed to reproduce Ennis's results with four experts from reputable laboratories executing the experiment under the supervision of James Randi.  Benveniste later used a robot to prepare his samples and found that the results varied depending on who was operating the robot. His supporters see this result as suggesting that the experimenter may have an effect on the water sample, which could explain why some experimenters are able to reproduce his findings and some are not. The vast majority of scientists see such claims as typical of pseudoscience.
In 2003 the British Journal of Clinical Pharmacology (Vol. 56, pp. 562-568) published a well-controlled trial  into the proving effects of Belladonna 30C. The trial concluded that no such effects existed.
In the same year Thorax (Vol. 58, pp. 317-231) published a study  into the treatment of asthma. The study was randomized, double-blind and placebo-controlled and, to address one criticism of conventional scientific methods, allowed for individualisation of the remedies. No evidence was found that remedies prescribed by experienced homeopathic practitioners were superior to a placebo. Other researchers criticized the study as being by its nature relatively insensitive.  Specifically, because of the ethical objections to denying medication to high-risk patients, only subjects with mild or moderate asthma were chosen for the study, making any improvement difficult to identify.
Later in 2003, the journal Physica A (Vol. 323, pp. 67-74) published a paper  by Swiss chemist Louis Rey, in which the author claimed to observe that salt solutions diluted to homeopathic levels retained the ability to suppress a phenomenon known as thermoluminescence. This has been taken by some as a proof of the ability of water to retain a "memory" of sorts, even if all other molecules have been diluted out of the solution. Rey's experiments have not been independently replicated to date, and the paper does not give any details on the tests of reproducibility made by the author. Furthermore, the measurements were not done blind and the effects could conceivably be due to contamination. 
Misconceptions about homeopathy
Substances used in the preparation of homeopathic remedies
Many producers of homeopathic remedies also produce other types of alternative remedies, under the same brand name, which leaves the general public often confused about what homeopathy really is. A common misconception is that homeopathic remedies use only (natural and thus presumed by some to be safe) herbal components, but that is herbology. While herbs are used in homeopathy, there is also use of non-biological substances (such as salts) and components of animal origin, such as duck liver in the popular remedy oscillococcinum. Homeopathy also uses substances of human origin, which are called nosodes. Another difference is that though both do use herbs, in herbology measurable amounts of the herb(s) are in the remedy, while in homeopathy it gets diluted beyond measurable quantities.
Some people have the opposite misconception, that homeopathic remedies are only based on toxic substances like snake venom or mercury.
Claims of homeopathy for marketing purposes
Since the term homeopathy is well known and has good marketing value, the public can be further confused by people who misuse the term, such as homeopathic dentists, homeopathic electro-acupuncturists etc. Classical homeopaths claim only remedies prepared in accordance with the laws and rules of Dr. Hahnemann can be called homeopathic.
The practice of mainstream medicine that most closely resembles homeopathy is vaccination. The vaccine must be closely related to the disease against which it is to protect and must be given in a very small dose to be effective. These characteristics are reminiscent of the law of similars and the law of infinitesimals. In fact Hahnemann himself interpreted the introduction of vaccination by Edward Jenner in 1798 as a confirmation of the law of similars. Modern homeopaths view vaccination and homeopathy as fundamentally different.
Although Hahnemann originally introduced low dosages in order to reduce side effects, he later believed, as do most homeopaths today, that remedies are most effective if they have been dynamized to such a degree that they have no direct chemical effect. From this point of view, the need to keep the dosage of vaccine low is simply the standard requirement to avoid consuming an excessive amount of any conventional drug. The dosage of a vaccine is still much higher than typical homeopathic dosage, and the vaccine has been diluted but not dynamized.
Homeopathic critics of vaccination also consider the resemblence to the law of similars to be superficial. In most cases a vaccine is not intended to cure a disease at all, but rather to prevent it by preparing the immune system of a healthy organism to meet an attack by a pathogen in the future. Furthermore, the vaccine is usually a bacterium or virus whose capability to produce symptoms has deliberately been weakened while still providing enough information to the immune system. The "similarity" of the vaccine and the disease in terms of symptoms is thus reduced.
The difference between homeopathy and vaccination is best illustrated by a comparison with nosodes, which are made from active (not deactivated) pathogens, are applied after the onset of a disease to cure it (not before to prevent it), and are administered at zero (not merely low) dosage in a chemical sense.
- A recent and rather fair article on homeopathy testing from the Annals of Internal Medicine
- BBC's Horizon on homeopathy (transcripts, discussion, etc.)
- Homeopathy In Perspective — critical online book, covering the history and present state of homeopathy
- FDA's view of homeopathy
- Homéopathe International — The English language version of Homéopathe International, is the best academic web site on Homeopathy on the Internet.
- Introduction and Information on Homeopathy
- North American Society of Homeopaths
- Extensive Homeopathy Links from The Holistic Medicine Resource Center
- Information and Discussion Forum
- Complementary Medicine - Therapies: Homeopathy BBC's "Complementary Medicine" article on Homeopathy
- Referrals to Certified Classical Homeopaths
- Alliance of Registered Homeopaths
- A skeptic's view of homeopathy
- Magical Thinking in Complementary and Alternative Medicine
- Quackwatch on homeopathy
- HomeoWatch — A Skeptical Guide to Homeopathic History, Theories, and Current Practices, operated by Stephen Barrett, M.D. (founder of Quackwatch)
- H2G2 entry on homeopathy.
- The Skeptics Dictionary
- "The Scientific Evidence on Homeopathy" - American Council on Science and Health
- A close look at homeopathy
- Dilution or Delusion?
- National Council Against Health Fraud Position Paper on Homeopathy