Homeopathy
Homeopathy (also homopathy or homoeopathy; from the Greek , homoios, "similar" + , pathos, "suffering" or "disease") is a form of alternative medicine first defined by Samuel Hahnemann in the 18th century. Homeopathic practitioners contend that an ill person can be treated using a substance that can produce, in a healthy person, symptoms similar to those of the illness.  According to homeopaths, serial dilution, with shaking between each dilution, removes the toxic effects of the remedy while the qualities of the substance are retained by the diluent (water, sugar, or alcohol). The end product is often so diluted that materially it is indistinguishable from pure water, sugar or alcohol. Practitioners select treatments according to a patient consultation that explores the physical and psychological state of the patient, both of which are considered important to selecting the remedy.
Claims for efficacy of homeopathic treatment beyond the placebo effect are unsupported by scientific and clinical studies, although meta-analyses of homeopathy, which compare the results of many studies, face difficulty in controlling for the combination of publication bias and the fact that most of these studies suffer from serious shortcomings in their methods. The ideas behind homeopathy are scientifically implausible and "diametrically opposed to modern pharmaceutical knowledge". The lack of convincing scientific evidence supporting its efficacy, and its contradiction of basic scientific principles, have caused homeopathy to be regarded as pseudoscience, or, in the words of a 1998 medical review, as "placebo therapy at best and quackery at worst".
Current usage around the world varies from two percent of people in Britain and the United States using homeopathy in any one year, to 15 percent in India, where homeopathy is now considered part of Indian traditional medicine. Homeopathic remedies are generally considered safe, with rare exceptions; however, homeopaths have been criticised for putting patients at risk by advising them to avoid conventional medicine, such as vaccinations, anti-malarial drugs and antibiotics.  In many countries, the laws that govern regulation and testing of conventional drugs often do not apply to homeopathic remedies.

# History

## 18th-century medicine
At the time of the inception of homeopathy, the late 1700s, mainstream medicine employed such measures as bloodletting and purging, the use of laxatives and enemas, and the administration of complex mixtures, such as theriac, which was made from 64 substances including opium, myrrh, and viper's flesh. Such measures often worsened symptoms and sometimes proved fatal. While the virtues of these treatments had been extolled for centuries, Hahnemann rejected such methods as irrational and unadvisable. Instead, he favored the use of single drugs at lower doses and promoted an immaterial, vitalistic view of how living organisms function, believing that diseases have spiritual, as well as physical causes. (At the time, vitalism was part of mainstream science; in the twentieth century, however, medicine discarded vitalism, with the development of microbiology, the germ theory of disease, and advances in chemistry.) Hahnemann also advocated various lifestyle improvements to his patients, including exercise, diet, and cleanliness.

## Hahnemann's concept
Samuel Hahnemann conceived of homeopathy while translating a medical treatise by Scottish physician and chemist William Cullen into German. Being sceptical of Cullens theory concerning cinchonas action in malaria, Hahnemann ingested some of the bark specifically to see if it cured fever "by virtue of its effect of strengthening the stomach".
 Upon ingesting the bark, he noticed few stomach symptoms, but did experience fever, shivering and joint pain, symptoms similar to some of the early symptoms of malaria, the disease that the bark was ordinarily used to treat. From this, Hahnemann came to believe that all effective drugs produce symptoms in healthy individuals similar to those of the diseases that they can treat. This later became known as the "law of similars", the most important concept of homeopathy. The term "homeopathy" was coined by Hahnemann and first appeared in print in 1807, although he began outlining his theories of "medical similars" in a series of articles and monographs in 1796.
Hahnemann began to test what effects substances produced in humans, a procedure which would later become known as "proving". These time-consuming tests required subjects to clearly record all of their symptoms as well as the ancillary conditions under which they appeared. Hahnemann saw this data as a way of identifying substances suitable for the treatment of particular diseases. The first collection of provings was published in 1805 and a second collection of 65 remedies appeared in his book, Materia Medica Pura, in 1810. Hahnemann believed that large doses of drugs that caused similar symptoms would only aggravate illness, and so he advocated extreme dilutions of the substances; he devised a technique for making dilutions that he believed would preserve a substance's therapeutic properties while removing its harmful effects, proposing that this process aroused and enhanced "spirit-like medicinal powers held within a drug". He gathered and published a complete overview of his new medical system in his 1810 book, The Organon of the Healing Art, whose 6th edition, published in 1921, is still used by homeopaths today.

## Rise to popularity and early criticism
During the 19th century homeopathy grew in popularity. In 1830, the first homeopathic schools opened, and throughout the 19th century dozens of homeopathic institutions appeared in Europe and the United States. Because of mainstream medicine's reliance on blood-letting and untested, often dangerous medicines, patients of homeopaths often had better outcomes than those of mainstream doctors. Homeopathic treatments, even if ineffective, would almost surely cause no harm, making the users of homeopathic medicine less likely to be killed by the medicine that was supposed to be helping them. The relative success of homeopathy in the 18th century may have led to the abandonment of the ineffective and harmful treatments of bloodletting and purging and to have begun the move towards more effective, scientific medicine.
In the early 19th century, homeopathy began to be criticised. Sir John Forbes, physician to Queen Victoria, said the extremely small doses of homeopathy were regularly derided as useless, laughably ridiculous and "an outrage to human reason". Professor Sir James Young Simpson said of the highly diluted drugs: "No poison, however strong or powerful, the billionth or decillionth of which would in the least degree affect a man or harm a fly." Nineteenth century American physician and author Oliver Wendell Holmes, Sr. was also a vocal critic of homeopathy and published an essay in 1842 entitled Homopathy, and its Kindred Delusions. The last school in the U.S. exclusively teaching homeopathy closed in 1920.

# General philosophy
Homeopathy is a vitalist philosophy in that it regards diseases and sickness to be caused by disturbances in a hypothetical vital force or life force in humans and that these disturbances manifest themselves as unique symptoms. Homeopathy contends that the vital force has the ability to react and adapt to internal and external causes, which homeopaths refer to as the "law of susceptibility". The law of susceptibility states that a negative state of mind can attract hypothetical disease entities called "miasms" to invade the body and produce symptoms of diseases. However, Hahnemann rejected the notion of a disease as a separate thing or invading entity and insisted that it was always part of the "living whole".

## Law of similars
Hahnemann observed from his experiments with cinchona bark, used as a treatment for malaria, that the effects he experienced from ingesting the bark were similar to the symptoms of malaria. He therefore reasoned that cure proceeds through similarity, and that treatments must be able to produce symptoms in healthy individuals similar to those of the disease being treated. Through further experiments with other substances, Hahnemann conceived of the "law of similars", otherwise known as "like cures like" (Template:Lang-la) as a fundamental healing principle. He believed that by inducing a disease through use of drugs, the artificial symptoms empowered the vital force to neutralise and expel the original disease and that this artificial disturbance would naturally subside when the dosing ceased.

## Miasms and disease
Hahnemann found as early as 1816 that the patients he treated through homeopathy still suffered from chronic diseases that he was unable to cure. In 1828, he introduced the concept of miasms, which he regarded as underlying causes for many known diseases. A miasm is often defined by homeopaths as an imputed "peculiar morbid derangement of our vital force". Hahnemann associated each miasm with specific diseases, with each miasm seen as the root cause of several diseases. According to Hahnemann, initial exposure to miasms causes local symptoms, such as skin or venereal diseases, but if these symptoms are suppressed by medication, the cause goes deeper and begins to manifest itself as diseases of the internal organs. Homeopathy contends that treating diseases by directly opposing their symptoms, as is sometimes done in conventional medicine, is not so effective because all "disease can generally be traced to some latent, deep-seated, underlying chronic, or inherited tendency". The underlying imputed miasm still remains, and deep-seated ailments can only be corrected by removing the deeper disturbance of the vital force.
Hahnemann's miasm theory remains disputed and controversial within homeopathy even in modern times. In 1978, Anthony Campbell, then a consultant physician at The Royal London Homeopathic Hospital, criticised statements by George Vithoulkas claiming that syphilis, when treated with antibiotics, would develop into secondary and tertiary syphilis with involvement of the central nervous system. This conflicts with scientific studies, which indicate that penicillin treatment produces a complete cure of syphilis in more than 90% of cases. Campbell described this as "a thoroughly irresponsible statement which could mislead an unfortunate layman into refusing orthodox treatment".
Originally Hahnemann presented only three miasms, of which the most important was "psora" (Greek for itch), described as being related to any itching diseases of the skin, supposed to be derived from suppressed scabies, and claimed to be the foundation of many further disease conditions. Hahnemann claimed psora to be the cause of such diseases as epilepsy, cancer, jaundice, deafness, and cataracts. Since Hahnemann's time, other miasms have been proposed, some replacing one or more of psora's proposed functions, including tubercular miasms and cancer miasms.

# Preparation of remedies

## Dilution and succussion
In producing treatments for diseases, homeopaths use a process called "dynamisation" or "potentisation" whereby the remedy is diluted with alcohol or water and then vigorously shaken by ten hard strikes against an elastic body in a process called "succussion". Hahnemann thought that the use of remedies which present symptoms similar to those of disease in healthy individuals would only intensify the symptoms and exacerbate the condition, so he advocated the dilution of the remedies. During the process of potentisation, homeopaths believe that the vital energy of the diluted substance is activated and its energy released by vigorous shaking of the substance. For this purpose, Hahnemann had a saddle maker construct a special wooden striking board covered in leather on one side and stuffed with horsehair.  Insoluble solids, such as quartz and oyster shell, are diluted by grinding them with lactose (trituration).
Three potency scales are in regular use in homeopathy. Hahnemann pioneered and always favoured the centesimal or "C scale", diluting a substance 1 part in a hundred of diluent at each stage. A 2C dilution requires a substance to be diluted to one part in one hundred, then some of that diluted solution is diluted by one part in one hundred. This works out to one part of the original solution to ten thousand parts (100x100) of diluent. A 6C dilution repeats the process six times, ending up with one part in 1,000,000,000,000. (100  100  100  100  100  100, or 1006) Other dilutions follow the same pattern. In homeopathy, a solution is described as higher potency the more dilute it is. Higher potencies - that is more dilute substances - are considered to be stronger deep-acting remedies.
Hahnemann advocated carrying out provings of remedies using 30C dilutions and a common homeopathic treatment for the flu is a 200C dilution of duck liver, called Oscillococcinum in homeopathy. Comparing these levels of dilution to the number of molecules present in the initial solution, 50 mL of a 12C solution of Natrum muriaticum (sodium chloride) contains on average only about one molecule of the original substance. The chances of a single molecule of the original substance remaining in a 15C dilution would be roughly 1 in 2 million, and less than one in a billion billion billion billion (1036) for a 30C solution. For a perspective on these numbers, there are on the order of 1032 molecules of water in an Olympic-size swimming pool and if such a pool were filled with a 15C homeopathic remedy, to have a 63% chance of consuming at least one molecule from the original substance, one would need to swallow 1% of the volume of such a pool, or roughly 25 metric tons of water.
For more perspective, 1 ml of a solution which has gone through a 30C dilution would have been diluted into a volume of water equal to that of a cube of 1,000,000,000,000,000,000 metres per side, or about 106 light years. Thus, homeopathic remedies of standard dilutions contain, with overwhelming probability, only water (or alcohol). Practitioners of homeopathy believe that this water retains some "essential property" of the original substance, due to the shaking after each dilution. Hahnemann believed that the dynamisation or shaking of the solution caused a "spirit-like" healing force to be released from within the substance. He thought that even after every molecule of the previous substance has been removed from the water, the spiritual healing force still remained.
Some homeopaths developed a decimal scale (D or X), diluting the substance to ten times its original volume each stage. The D or X scale dilution is therefore half that of the same value of the C scale; for example, "12X" is the same level of dilution as "6C". Hahnemann never used this scale but it was very popular throughout the 19th century and still is in Europe. This potency scale appears to have been introduced in the 1830s by the American homeopath, Dr. Constantine Hering. In the last ten years of his life, Hahnemann also developed a quintamillesimal (Q) or LM scale diluting the drug 1 part in 50,000 parts of diluent. A Q scale dilution is 2.35 times that of a C scale one, for example "20Q" is the same potency as "47C".
Not all homeopaths advocate extremely high dilutions. Many of the early homeopaths were originally doctors and generally tended to use lower dilutions such as "3X" or "6X", rarely going beyond "12X". The split between lower and higher dilutions followed ideological lines with the former stressing pathology and a strong link to conventional medicine, while the latter emphasised vital force, miasms and a spiritual interpretation of disease.

### Coverage in the mainstream press
The BBC's Horizon and ABC's 20/20 broadcast programs described scientific testing of homeopathic dilutions that were unable to differentiate these dilutions from water.

## Provings
In order to determine which specific remedies could be used to treat which diseases, Hahnemann experimented on himself and others for several years, before using remedies on patients. His experiments did not initially consist of giving remedies to the sick, because he thought that the most similar remedy, by virtue of its ability to induce symptoms similar to the disease itself, would make it impossible to determine which symptoms came from the remedy and which from the disease itself. Therefore, sick people were excluded from the provings. The method used for determining which remedies were suitable for specific diseases was called "proving". A homeopathic proving is the method by which the profile of a homeopathic remedy is determined. The word "proving" derives from the German word "Prufung" meaning "test".
During the process of proving, Hahnemann used healthy volunteers who were given remedies, often in molecular doses, although he later advocated proving with remedies at a 30C dilution, and the resulting symptoms were compiled by observers into a "Drug Picture". During the process the volunteers were observed for months at a time and were made to keep extensive journals detailing all of their symptoms at specific times during the day. During the tests volunteers were forbidden from consuming coffee, tea, spices, or wine. They were also not allowed to play chess, because Hahnemann considered it to be "too exciting", though they were allowed to drink beer and were encouraged to moderately exercise. After the experiments were over, Hahnemann made the volunteers offer their hands and take an oath swearing that what they reported in their journals was the truth, at which time he would interrogate them extensively concerning their symptoms.
Provings have been described as important in the development of the clinical trial, due to their early use of simple control groups, systematic and quantitative procedures, and some of the first application of statistics in medicine. The lengthy records of self-experimentation by homeopaths have occasionally proven useful in the development of modern drugs: For example,  evidence nitroglycerin might be useful as a treatment for angina was discovered by looking through homeopathic provings, though homeopaths themselves never used it for that purpose at that time.
The first recorded provings were published by Hahnemann in his 1796 Essay on a New Principle. His Fragmenta de viribus (1805) contained the results of 27 provings, and his 1810 Materia Medica Pura contained 65. 217 remedies underwent provings for James Tyler Kent's 1905 Lectures on Homoeopathic Materia Medica, and newer substances are continually added to contemporary versions.

## Repertory
A compilation of reports of many homeopathic provings is known as a homeopathic materia medica. In practice the usefulness of such a compilation is limited because a practitioner does not need to look up the symptoms for a particular remedy, but rather to explore the remedies for a particular symptom. This need is filled by the homeopathic repertory, which is an index of symptoms, listing after each symptom those remedies that are associated with it. Repertories are often very extensive and may include data from clinical experience in addition to provings. There is often lively debate among the compilers of a repertory and interested practitioners over the veracity of a particular inclusion. The first symptomatic index of the homeopathic materia medica was arranged by Hahnemann. Soon after, one of his students Clemens von Bonninghausen, created the Therapautic Pocket Book, another homeopathic repertory. The first such Homeopathic Repertory was Dr. George Jahr's Repertory, published in 1835 in German and then again in 1838 in English and edited by Dr. Constantine Hering. This version was less focused on disease categories and would be the forerunner to Kent's later works. It consisted of three large volumes. Such repertories increased in size and detail as time progressed.

# Treatments
Homeopathic treatments generally begin with a detailed examinations of their patients' histories, including questions regarding their physical, mental and emotional states, their one's life circumstances and any physical/emotional illnesses. The homeopath then translates this information into a complex formula of mental and physical symptoms, including likes, dislikes, innate predispositions and even body type. The goal is to develop a comprehensive representation of each individual's overall health. This information can then be compared with similar established data in the drug provings found in the homeopathic materia medica. Assisted by further dialogues with the patient, the homeopath then aims to find the one drug most closely matching the "symptom totality" of the patient. There are many methods for determining the most-similar remedy (the simillimum), and homeopaths sometimes disagree. This is partly due to the complexity of the "totality of symptoms" concept. That is, homeopaths do not use all symptoms, but decide which are the most characteristic. This subjective evaluation of case analysis relies on knowledge and experience of the homeopath doing the diagnosis.
Some diversity in approaches to treatments exists among homeopaths. So called "classical" homeopathy generally involves detailed examinations of a patient's history and infrequent doses of a single remedy as the patient is monitored for improvements in symptoms. While "clinical" homeopathy involves combinations of remedies to address the various symptoms of an illness.

## Remedies
"Remedy" is a technical term used in homeopathy to refer to a substance prepared with a particular procedure and intended for treating patients. Homeopathic practitioners rely on two types of reference when prescribing remedies. The Homeopathic Materia Medicae which is comprised of alphabetical indexes of "drug pictures" organised by remedy and describe the symptom patterns associated with individual remedies. They also rely on homeopathic repertories which consist of indexes of symptoms of diseases and listing remedies associated with specific symptoms.
Homeopathy uses many animal, plant, mineral, and synthetic substances in its remedies. Examples include Natrum muriaticum (sodium chloride or table salt), Lachesis muta (the venom of the bushmaster snake), Opium, and Thyroidinum (thyroid hormone). Homeopaths also use treatments called nosodes (from the Greek nosos, disease) made from diseased or pathological products such as fecal, urinary, and respiratory discharges, blood, and tissue. Homeopathic remedies prepared from healthy specimens are called Sarcodes.
Some modern homeopaths have considered more esoteric substances, known as "imponderables" because they do not originate from a material but from electromagnetic energy presumed to have been "captured" by alcohol or lactose. Examples include X-rays, sunlight, and electricity. Recent ventures by homeopaths into even more esoteric substances include thunderstorms (prepared from collected rainwater). Today there are about 3,000 different remedies commonly used in homeopathy. Some homeopaths also use techniques that are regarded by other practitioners as controversial. These include paper remedies, where the substance and dilution are written on a piece of paper and either pinned to the patient's clothing, put in their pocket, or placed under a glass of water that is then given to the patient, as well as the use of radionics to prepare remedies. Such practices have been strongly criticised by classical homeopaths as unfounded, speculative and verging upon magic and superstition.

## Isopathy
Isopathy is a therapy derived from homeopathy and was invented by Johann Joseph Wilhelm Lux in the 1830s. Isopathy differs from homeopathy in general in that the remedies are made up either from things that cause the disease, or from products of the disease, such as pus. Many so-called "homeopathic vaccines" are a form of isopathy.

## Tautopathy
Tautopathy is a practice of alternative medicine that is similar to homeopathy in that it uses very diluted substances to treat illness. However, tautopathy does not rely on the "law of similars", as homeopathy does. According to practitioners of Tautopathy, dilute solutions of lead and arsenic can cause the body to secrete excess amounts of these toxic metals.

## Flower remedies
Flower remedies are produced by placing flowers in water and exposing them to sunlight. The most famous of these are the Bach flower remedies, which were developed by the homeopath Edward Bach. The relationship between these remedies and homeopathy is controversial. On the one hand, the proponents of these remedies share homeopathy's vitalist world-view and the remedies are claimed to act through the same hypothetical "vital force". However, although many of the same plants are used as in homeopathy, the method of preparation is somewhat different, with Bach flower therapies supposedly being prepared in "gentler" ways, such as placing flowers in bowls of sunlit water, and so on. There is no convincing scientific or clinical evidence for flower remedies being effective.

## Veterinary use
The idea of using homeopathy as a treatment for other animals, termed veterinary homeopathy, dates back to the inception of homeopathy as Hahnemann himself wrote and spoke of the use of homeopathy in animals other than humans. In the USA veterinary homeopathy is used by veterinarian members of the Academy for Veterinary Homeopathy and/or the American Holistic Veterinary Medical Association. The FDA has not approved homeopathic products as veterinary medicine in the US. In the UK, veterinary surgeons who use homeopathy belong to the Faculty of Homeopathy and/or to the British Association of Homeopathic Veterinary Surgeons. Animals may only be treated by qualified veterinary surgeons in the UK and some other countries. Internationally, the body that supports and represents homeopathic veterinarians is the International Association for Veterinary Homeopathy. The use of homeopathy in veterinary medicine is controversial, as there has been little scientific investigation and current research in the field is not of a high enough standard to provide reliable data. Other studies have also found that giving animals placebos can play active roles in influencing pet owners to believe in the effectiveness of the treatment when none exists.

# Medical and scientific analysis
Homeopathy is unsupported by modern scientific research. The extreme dilutions used in homeopathic preparations usually leave none of the active ingredient (atoms, ions or molecules) in the final product. The idea that any biological effects could be produced by these preparations is inconsistent with the observed dose-response relationships of conventional drugs. The proposed rationale for these extreme dilutions - that the water contains the "memory" or "vibration" from the diluted ingredient - is also counter to the laws of chemistry and physics. Thus critics contend that any positive results obtained from homeopathic remedies are purely due to the placebo effect. Critics cite the lack of viable scientific studies for the effectiveness of homeopathic remedies as evidence that they are not effective and that any positive effects are due to the placebo effect. Critics also contend that homeopathy is inherently dangerous, because homeopaths offer a false hope that may discourage or delay proper treatment.

## High dilutions
The extremely high dilutions in homeopathy have been a main point of criticism. Homeopaths believe that the methodical dilution of a substance, beginning with a 10% or lower solution and working downwards, with shaking after each dilution, produces a therapeutically active "remedy", in contrast to therapeutically inert water. However, homeopathic remedies are usually diluted to the point where there are no molecules from the original solution left in a dose of the final remedy. Since even the longest-lived noncovalent structures in liquid water at room temperature are only stable for a few picoseconds, critics have concluded that any effect that might have been present from the original substance can no longer exist. Furthermore, since water will have been in contact with millions of different substances throughout its history, critics point out that any glass of water is therefore an extreme dilution of almost any conceivable substance, and so by drinking water one would, according to homeopathic principles, receive treatment for every imaginable condition. Proponents of homeopathy, including Rustum Roy, maintain that water has a memory effect beyond the presence of individual molecules of the dissolved substance, but this is unsupported by experimental evidence.
Homeopathy contends that higher dilutions (fewer potential molecules in each dose) result in stronger medicinal effects. This idea is inconsistent with the observed dose-response relationships of conventional drugs, where the effects are dependent on the concentration of the active ingredient in the body. This dose-response relationship has been confirmed in thousands of experiments on organisms as diverse as nematodes, rats, and humans.
Physicist Robert L. Park, former executive director of the American Physical Society, has noted that "since the least amount of a substance in a solution is one molecule, a 30C solution would have to have at least one molecule of the original substance dissolved in a minimum of 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 molecules of water. This would require a container more than 30,000,000,000 times the size of the Earth." Park has also noted that "to expect to get even one molecule of the 'medicinal' substance allegedly present in 30X pills, it would be necessary to take some two billion of them, which would total about a thousand tons of lactose plus whatever impurities the lactose contained". The laws of chemistry state that there is a limit to the dilution that can be made without losing the original substance altogether. This limit, which is related to Avogadro's number, corresponds to homeopathic potencies of 12C or 24X (1 part in 1024).Template:Ref label

## Research on medical effectiveness
The medical effectiveness of homeopathy has been a point of contention since its inception, and researchers have subjected the system to close scrutiny. One of the earliest studies concerning homeopathic medicine was sponsored by the British government during World War II in which volunteers tested the effectiveness of homeopathic remedies against diluted mustard gas burns. More recent controlled clinical trials on homeopathy have shown poor results, showing slight-to-no differences between homeopathic remedies and placebo.
Meta-analyses, which analyse large groups of studies and draw conclusions based on the results as a whole, have been used to evaluate the effectiveness of homeopathy. Early meta-analyses investigating homeopathic remedies showed slightly positive results among the studies examined, but such studies have warned that it was impossible to draw conclusions due to low methodological quality and difficulty in controlling for publication bias in the studies reviewed. One of the positive meta-analyses, by Linde, et al, was later corrected by the authors, who wrote:
A recent meta-analysis of clinical trials on the effectiveness of homeopathy has shown that earlier clinical trials showed signs of major weakness in methodology and reporting, and that homeopathy trials were less randomized and reported less on dropouts than other types of trials.
In 2005 The Lancet medical journal published a meta-analysis of 110 placebo-controlled homeopathy trials and 110 matched conventional-medicine trials based upon the Swiss government's Program for Evaluating Complementary Medicine, or PEK. The study concluded that its findings were compatible with the notion that the clinical effects of homeopathy are nothing more than placebo effects. However, this last study has been criticised "for being methodologically flawed on many levels." "Of particular concern, the researchers eliminated 102 of 110 homeopathic trials and based their conclusions on only the 8 largest high-quality trials without clearly identifying the criteria by which these trials were selected or the identity of these trials. Odds ratios calculated before the exclusions (on all 110 trials) do not support their ultimate conclusion that homeopathic interventions are no better than placebo"
A 2006 meta-analysis of six trials evaluating homeopathic treatments to reduce cancer therapy side effects following radiotherapy and chemotherapy found "encouraging but not convincing" evidence in support of homeopathic treatment. However, variability in the methodological quality of the six studies provided "insufficient evidence to support clinical efficacy of homeopathic therapy in cancer care".
Since homeopathic remedies at dilutions higher than about D23 (10-23) contain no ingredients apart from the diluent (water, alcohol or sugar), there is no chemical basis for them to have any medicinal action. Newer randomized, double-blind, placebo-controlled trials using highly-diluted homeopathic preparations also fail to find clinical effects of the substances.
The Cochrane Library found insufficient clinical evidence to evaluate the efficacy of homeopathic treatments for asthma or dementia, or for the use of homeopathy in induction of labor. Other researchers found no evidence that homeopathy is beneficial for osteoarthritis, migraines or delayed-onset muscle soreness.
Health organisations such as UK's National Health Service, the American Medical Association, and the FASEB have issued statements of their conclusion that there is no convincing scientific evidence to support the use of homeopathic treatments in medicine.
Clinical studies of the medical efficacy of homeopathy have been criticised by some homeopaths as being irrelevant because they do not test "classical homeopathy". There have, however, been a number of clinical trials that have tested individualized homeopathy. A 1998 review
found 32 trials that met their inclusion criteria, 19 of which were placebo-controlled and provided enough data for meta-analysis. These 19 studies showed a pooled odds ratio of 1.17 to 2.23 in favor of individualized homeopathy over the placebo, but no difference was seen when the analysis was restricted to the methodologically best trials. The authors concluded "that the results of the available randomized trials suggest that individualized homeopathy has an effect over placebo. The evidence, however, is not convincing because of methodological shortcomings and inconsistencies."
Dr. Jack Killen, acting deputy director of the National Center for Complementary and Alternative Medicine, says homeopathy "goes beyond current understanding of chemistry and physics". He adds, "There is, to my knowledge, no condition for which homeopathy has been proven to be an effective treatment."

# Research on effects in other biological systems
While some articles have suggested that homeopathic solutions of high dilution can have statistically significant effects on organic processes including the growth of grain, histamine release by leukocytes, and enzyme reactions, such evidence is disputed since attempts to replicate them have failed.
In 1987, French immunologist Jacques Benveniste submitted a paper to the journal Nature while working at INSERM. The paper purported to have discovered that basophils released histamine when exposed to a homeopathic dilution of anti-immunoglobulin E, a type of white blood cell. The journal editors, sceptical of the results, requested that the study be replicated in a separate laboratory. Upon replication in four separate laboratories the study was published. Still sceptical of the findings, Nature assembled an independent investigative team to determine the accuracy of the research, consisting of Nature editor and physicist Sir John Maddox, American scientific fraud investigator and chemist Walter Stewart, and sceptic and magician James Randi. After investigating the findings and methodology of the experiment, the team found that the experiments were "statistically ill-controlled", "interpretation has been clouded by the exclusion of measurements in conflict with the claim", and concluded, "We believe that experimental data have been uncritically assessed and their imperfections inadequately reported." James Randi stated that he doubted that there had been any conscious fraud, but that the researchers had allowed "wishful thinking" to influence their interpretation of the data.

## Ethical and safety issues
As homeopathic remedies usually contain only water and/or alcohol, they are thought to be generally safe. Only in rare cases are the original ingredients present at detectable levels. In one such case, an unusually undiluted (1:100 or "2X") solution of zinc gluconate, marketed as Zicam Nasal Spray, allegedly caused a small percentage of users to lose their sense of smell. There were 340 cases settled out of court for 12 million U.S. dollars.
Critics of homeopathy have cited other concerns over homeopathic remedies, most seriously, cases of patients of homeopathy failing to receive proper treatment for diseases that it is claimed could have been diagnosed or cured with conventional medicine. Several surveys demonstrate that some (particularly non-physician) homoeopaths advise their patients against immunisation. Some homeopaths suggest that vaccines be replaced with homeopathically diluted "nosodes", created from dilutions of biological agents - including material such as vomit, feces or infected human tissues. While Hahnemann was opposed to such preparations, modern homeopaths often use them and there is no evidence to indicate they have any beneficial effects. Cases of homeopaths advising against the use of anti-malarial drugs have been identified. This puts visitors to the tropics who take this advice in severe danger, since homeopathic remedies are completely ineffective against the malaria parasite. Also, in one case in 2004, a homeopath instructed one of his patients to stop taking conventional medication for a heart condition, writing in his advice, "She just cannot take ANY drugs  I have suggested some homeopathic remedies. I feel confident that if she follows the advice she will regain her health." The patient suffered a fatal heart attack four months later, caused by this stoppage of her medication.
In 1978, Anthony Campbell, then a consultant physician at The Royal London Homeopathic Hospital, criticised statements made by George Vithoulkas to promote his homeopathic treatments. Vithoulkas stated that syphilis, when treated with antibiotics, would develop into secondary and tertiary syphilis with involvement of the central nervous system. Campbell described this as a thoroughly irresponsible statement which could mislead an unfortunate layman into refusing conventional medical treatment. This claim echoes the idea that treating a disease with external medication used to treat the symptoms would only drive it deeper into the body and conflicts with scientific studies, which indicate that penicillin treatment produces a complete cure of syphilis in more than 90% of cases.
A 2006 review by W. Steven Pray of the College of Pharmacy at Southwestern Oklahoma State University recommends that pharmacy colleges include a required course in unproven medications and therapies, that ethical dilemmas inherent in recommending products lacking proven safety and efficacy data be discussed, and that students should be taught where unproven systems such as homeopathy depart from evidence-based medicine.

# Prevalence and legal trends
Homeopathic medicine is fairly common in some countries while being uncommon in others; is highly regulated in some countries and mostly unregulated in others. Regulations vary in Europe depending on the country. In some countries, there are no specific legal regulations concerning the use of homeopathy, while in others, licenses or degrees in conventional medicine from accredited universities are required. In Austria and Germany, no specific regulations exist, while France and Denmark mandate licenses to diagnose any illness or dispense of any product whose purpose is to treat any illness. Some homeopathic treatment is covered by the national insurance coverage of several European countries, including France, the United Kingdom, Denmark, and Luxembourg. In other countries, such as Belgium, homeopathy is not covered. In Austria, public insurance requires scientific proof of effectiveness in order to reimburse medical treatments, but exceptions are made for homeopathy. Two countries which formerly offered homeopathy under their public health insurance schemes have withdrawn this privilege. At the start of 2004, homeopathic medications, with some exceptions, were no longer covered by German public health insurance, and in June 2005, the Swiss Government, after a 5-year trial, withdrew insurance coverage for homeopathy and four other complementary treatments, stating that they did not meet efficacy and cost-effectiveness criteria, though additional insurance can be bought to cover such treatments provided by a medical doctor.

## Outline of past prevalence in Great Britain
In Britain homeopathy was first established by Dr. Frederick Quin around 1827, although two Italian homeopathic doctors (Drs Romani and Roberta) had been employed two years previously by the Earl of Shrewsbury based at Alton Towers in North Staffordshire. Homeopathy in Britain quickly became the preferred medical treatment of the upper classes, as well as the aristocracy and retained an elite clientele, including members of the royal family.
At its peak in the 1870s, Britain had numerous homeopathic dispensaries and small hospitals as well as large busy hospitals in Liverpool, Birmingham, Glasgow, London and Bristol.

## Contemporary prevalence

### United Kingdom
The NHS currently operates five homeopathic hospitals. The largest organisation of homeopaths in the United Kingdom, the Society of Homeopaths, was founded in 1978. The London-based Faculty of Homeopathy has over 1,400 members and was incorporated by an Act of Parliament in 1950. According to a 2006 study, forty nine percent of Scottish medical practices prescribed homeopathic remedies. During the study period, 0.22% of patients were prescribed at least one homeopathic remedy; of that number, 16 percent were children. The study concluded that critical review of Homeopathy's role in the Scottish branch of the national health care system was needed.

### Australia
According to one study, about 4.4% of Australian adults have used homeopathic remedies at least once in their lives, including 1.2% that sought treatment exclusively from homeopathic practitioners.

### Canada
In Canada, a study detailing the use of alternative medicines by children in Quebec found that 11% of the sampled 1911 children used alternative medicines, and 25% of those who did use alternative medicines used homeopathy. The study also pointed out that homeopathy is more commonly used in children in Canada than in adults, of whom only 19% of alternative medicine users used homeopathy. Homeopathy is not officially recognised by Federal Food and Drugs Act in Canada and physicians who choose to use alternative medicines such as homeopathy must follow guidelines set by their province's College of Physicians and Surgeons. Provincial health care generally does not cover homeopathy.

### South America
Some countries in South America, such as Argentina, allow only professional doctors who are qualified and have graduated from a recognised medical school to practice homeopathy. Homeopathy has been regulated in other South American countries, such as Colombia, since the beginning of the 20th century. In Brazil, homeopathy is included in the national health system, and since 1991, physicians who want to practice homeopathy must complete 2,300 hours of education prior to receiving the proper licenses.

### Mexico
In Mexico, homeopathy is currently integrated into the national health care system. In 1985, a presidential decree established the first homeopathic school as well as regulations specifying training requirements for homeopathic doctors. Of those individuals who use complementary alternative medicines, over 26% use homeopathy.

### United States
In the United States, homeopathy is much less common, where the percentage of people seeking homeopathic treatment declined from 3.4% in 1997 to 1.7% in 2002. Homeopathy was first established in the United States by Dr. Hans Burch Gram in 1825 and rapidly gained popularity, partly because conventional medicine of the time was inherently risky. The height of its influence was the end of the 19th century where hardly any city with over 50,000 people was without a homeopathic hospital. In 1890, there were 93 regular schools, 14 of them were fully homeopathic and 8 of them were eclectic. In 1900, there were 121 regular schools, with 22 of them being homeopathic and 10 eclectic. The use of homeopathy in the United States among adults is about 0.3%. According to one study, in 1990, 0.7% of individuals used homeopathy in the year prior to being questioned; in 1997, 3.4% had used homeopathy at least once in the previous year. According to the same study, of those who used homeopathy, 31.7% had seen a homeopathic practitioner in the past year in 1990 and the number dropped to 16.5 by 1997.
In the United States, homeopathic remedies, like all health-care products, are regulated by the Food and Drug Administration. However, the FDA treats homeopathic remedies very differently from conventional medicines. Homeopathic products do not need FDA approval before sale; they do have to be proven safe per the Dietary Supplement Health and Education Act of 1994, but they do not have to prove efficacy. Homeopathic remedies do not have to be labeled with an expiration date, and they do not have to undergo finished product testing to verify contents and strength. All of these are voluntary actions done by the manufacturer. The manufacturer is required to have all ingredients on the label; however, it might not specify which ones are active. In the USA, only homeopathic medicines that claim to treat self-limiting conditions may be sold over-the-counter; homeopathic medicines that claim to treat a serious disease can be sold only by prescription. A memorandum, written in 1985 by attorneys for the American Association of Homeopathic Manufacturers, describes a meeting between the AAHP attorneys and high-ranking FDA officials to discuss whether homeopathic products must be proven effective to remain legally marketable. Such negotiations led to the issuance in 1988 (revised in 1995) of an FDA Compliance Policy Guide that permits homeopathic products "intended solely for self-limiting disease conditions amenable to self-diagnosis (of symptoms) and treatment" to be marketed as nonprescription drugs. In 2001, the FDA published a comprehensive review of mercury compounds in homeopathic drugs. This report indicated that nearly all examined compounds derived from the use of mercury. However, due to the extreme dilution of materials, the presence of mercury in the finished product would be minimal. At present the FDA Health Fraud Division only pursues claims which may cause direct harm to consumers through their use. Homeopathic drugs, largely regarded as equivalent to placebos, are not considered under these guidelines. Due to the significant dilution of the products, the agents become practically immeasurable: the harmful effects of homeopathic drugs is more likely to be that patients avoid conventional treatments.

### Asia
In Asia, the use of homeopathic treatments is increasing, especially in India. Homeopathy arrived in India with Dr John Martin Honigberger in Lahore, in 18291830. India has the largest homeopathic infrastructure in the world, with low estimates at about 64,000, but going as high as 300,000 practising homeopaths. In addition, there are 180 colleges teaching courses, and 7500 government clinics and 307 hospitals which dispense homeopathic remedies. In Malaysia, homeopathy was introduced during World War II and was brought by Indians via the British army.

### Africa
In South Africa, homeopathy is regulated by the Associated Health Service Professions Act of 1982, which was set up to provide a registration and licensing framework for health professions. During the 1960s, all homeopathic colleges were closed by the South African Medical Council. However, conventional medical doctors retained the right to use homeopathic treatments.