homeopathy, system of medicine whose fundamental principle is the law of similars—that like is cured by like. It was first given practical application by Samuel Hahnemann of Leipzig, Germany, in the early 19th cent. and was designated homeopathy to distinguish it from the established school of medicine which he called allopathy. The American Institute of Homeopathy was founded in 1844, and the practice of homeopathy was popularized in the United States by the physician and senator Royal S. Copeland (1868-1938). It had been observed that quinine given to a healthy person causes the same symptoms that malaria does in a person suffering from that disease; therefore quinine became the preferred treatment in malaria. When a drug was found to produce the same symptoms as did a certain disease, it was then used in very small doses in the treatment of that disease. U.S. medical schools do not presently emphasize the homeopathic approach, although it has become popular among some physicians in European and Asian nations and is widely used by the public in over-the-counter medications.

System of therapeutics founded in 1796 by Samuel Hahnemann on the principle that “like cures like.” That is, substances that in healthy persons would produce the symptoms from which the patient suffers are used to treat the patient. Hahnemann further stated that the potency of a curative agent increases as the substance is diluted. When it was introduced, homeopathy was a mild, welcome alternative to heavy-handed therapies such as bleeding, but it has since been criticized for focusing on symptoms rather than causes. With the rise of alternative medicine, it has seen a resurgence.

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Homeopathy (also homœopathy or homoeopathy; from the Greek ὅμοιος, hómoios, "similar" + πάθος, páthos, "suffering" or "disease") is a form of alternative medicine first defined by Samuel Hahnemann in the 18th century. A central thesis of homeopathy is that an ill person can be treated using a substance that can produce, in a healthy person, symptoms similar to those of the illness. 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. According to homeopaths, serial dilution, with shaking between each dilution, removes the toxic effects of the substance, while the essential qualities are retained by the diluent (water, sugar, or alcohol).

Claims to the efficacy of homeopathic treatment beyond the placebo effect are unsupported by the collective weight of scientific and clinical evidence. Common homeopathic preparations are often indistinguishable from the pure diluent because the purported medicinal compound is diluted beyond the point where there is any likelihood that molecules from the original solution are present in the final product; the claim that these treatments still have any pharmacological effect is thus scientifically implausible and violates fundamental principles of science, including the law of mass action. Critics also object that the number of high-quality studies that support homeopathy is small, the conclusions are not definitive, and duplication of the results, a key test of scientific validity, has proven problematic at best. The lack of convincing scientific evidence supporting its efficacy and its use of remedies without active ingredients have caused homeopathy to be regarded as pseudoscience or quackery.

Homeopathic remedies are generally considered safe, with rare exceptions, although homeopaths have been criticized for putting patients at risk by advising them to avoid conventional medicine, such as vaccinations, anti-malarial drugs and antibiotics. Regardless of whether homeopathic preparations are effective, they may make people feel better via the placebo effect. Thus, like any placebo, such remedies may improve symptoms subject to psychological or behavioral influences such as chronic pain, fatigue, anxiety or depression. In many countries, the laws that govern the regulation and testing of conventional drugs do not apply to homeopathic remedies. Current usage around the world varies from two percent of people in the United Kingdom and the United States using homeopathy in any one year to 15 percent in India, where it is considered part of Indian traditional medicine. In the UK, the National Health Service runs five homeopathic hospitals, and in the 1990s, between 5.9 and 7.5 percent of English family doctors are reported to have prescribed homeopathic remedies, a figure rising to at least 12 percent in Scotland. However, the number of homeopathic remedies prescribed by GPs in England dropped by over 40% between 2005 and 2007, with homeopathy accounting for only 0.006% of the total prescribing budget. In 2005, around 100,000 physicians used homeopathy worldwide, making it one of the most popular and widely used complementary therapies.

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 Venice treacle, 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 Cullen’s theory concerning cinchona’s 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 "homeopathic 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 then-current medicine's reliance on unscientific blood-letting and other untested, often dangerous treatments, patients of homeopaths often had better outcomes than those of the doctors of the time. Homeopathic remedies, even if ineffective, would almost surely cause no harm, making the users of homeopathic remedies less likely to be killed by the treatment 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, science based 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". 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 Homœopathy, and its kindred delusions. The last school in the U.S. exclusively teaching homeopathy closed in 1920.

Revival in the late 20th Century

Attempts to outlaw alternative forms of medicine in the USA failed and the Food, Drug, and Cosmetic Act of 1938 recognized homeopathic remedies as drugs. By the 1950s there were only 75 pure homeopaths practising in the USA. However, in the mid to late 1970s, homeopathy made a significant comeback and sales of some homeopathic companies increased tenfold. Homeopathy was also revived worldwide; for example, Brazil in the 1970s and Germany in the 1980s. The medical profession started to integrate such ideas in the 1990s and big mainstream pharmacies started competing for this business.

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 maintains 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" (similia similibus curentur) 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 maintains 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 created the centesimal or "C scale", diluting a substance by a factor of 100 at each stage. The centesimal scale was favored by Hahnemann for most of his life. A 2C dilution requires a substance to be diluted to one part in one hundred, and then some of that diluted solution is diluted by a further factor of one hundred. This works out to one part of the original solution mixed into 9,999 parts (100 × 100 −1) of the diluent. A 6C dilution repeats this process six times, ending up with the original material diluted by a factor of 100^-6=10^-12. Higher dilutions follow the same pattern. In homeopathy, a solution that is more dilute is described as having a higher potency. More dilute substances are considered by homeopaths to be stronger and deeper-acting remedies. The end product is often so diluted that it is indistinguishable from the dilutant (pure water, sugar or alcohol).

X Scale	C Scale	Ratio	Note
1X	—	1:10	described as low potency
2X	1C	1:100	called higher potency than 1X by homeopaths
6X	3C	10-6
8X	4C	10-8	allowable concentration of arsenic in US drinking water
12X	6C	10-12
24X	12C	10-24	Has a 60% probability of containing one molecule of original material.
60X	30C	10-60	Dilution advocated by Hahnemann for most purposes: this would require two billion doses per second to six billion people for 4 billion years to deliver a single molecule of the original material.
400X	200C	10-400	Dilution of popular homeopathic flu remedy Oscillococcinum

Hahnemann advocated 30C dilutions for most purposes (that is, dilution by a factor of 10⁶⁰). A popular homeopathic treatment for the flu is a 200C dilution of duck liver, marketed under the name Oscillococcinum.

Commonly, critics of homeopathy, as well as homeopaths themselves, attempt to illustrate the dilutions involved in homeopathy with examples. Hahnemann is reported to have joked that a suitable procedure to deal with an epidemic would be to empty a bottle of poison into Lake Geneva, if it could be succussed 60 times. Another example given by a critic of homeopathy states that a 12C solution is equivalent to a "pinch of salt in both the North and South Atlantic Oceans", which is approximately correct. One third of a drop of some original substance diluted into all the water on earth would produce a remedy with a concentration of about 13C. 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, 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 given dilution on the Q scale is roughly 2.35 times its designation on the C scale. For example a remedy described as "20Q" has about the same concentration as a "47C" remedy.

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 these experiments. The method used for determining which remedies were suitable for specific diseases was called "proving", after the original German word "Prüfung", meaning "test". A homeopathic proving is the method by which the profile of a homeopathic remedy is determined.

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. For James Tyler Kent's 1905 Lectures on Homoeopathic Materia Medica, 217 remedies underwent provings 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 Bönninghausen, created the Therapeutic 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

Homeopaths generally begin with detailed examinations of their patients' histories, including questions regarding their physical, mental and emotional states, their life circumstances and any physical/emotional illnesses. The homeopath then attempts to translate 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 lists 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 insurmountable complexity of the "totality of symptoms" concept. That is, homeopaths do not include all symptoms when determining which medicine is most appropriate, but decide for themselves which are the most characteristic. This subjective evaluation of case analysis relies on the knowledge and experience of the homeopath doing the diagnosis.

Some diversity in approaches to treatments exists among homeopaths. "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: Materia medicae and repertories. A homeopathic Materia medica is a collection of "drug pictures", organised alphabetically by remedy, that describes the symptom patterns associated with individual remedies. A homeopathic repertory is an index of disease symptoms that lists 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.

Flower remedies

Flower remedies can be 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; Hahnemann himself wrote and spoke of the use of homeopathy in animals other than humans. In the United States, 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. The lack of convincing scientific evidence supporting its efficacy and its use of remedies without active ingredients have caused homeopathy to be regarded as pseudoscience; quackery; or, in the words of a 1998 medical review, "placebo therapy at best and quackery at worst."

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.

Practitioners of homeopathy contend 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 multitudinous 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, is roughly equal to homeopathic potencies of 12C or 24X (1 part in 10²⁴).

Research on medical effectiveness

The 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 homeopathy 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 are not particularly convincing. For example NCCAM says: Positive results have been reported, but no single model has been sufficiently widely replicated, local models proposed are far from convincing, and the nonlocal models proposed would predict that it is impossible to nail down homeopathic effects with direct experimental testing. For example, while some reports presented data that suggested hoemopathic treatment of allergy was more effective than placebo, subsequent studies have questioned the conclusions.

Meta-analyses, in which large groups of studies are analysed and conclusions drawn 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 firm 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:

The evidence of bias [in homeopathic trials] weakens the findings of our original meta-analysis. Since we completed our literature search in 1995, a considerable number of new homeopathy trials have been published. The fact that a number of the new high-quality trials... have negative results, and a recent update of our review for the most “original” subtype of homeopathy (classical or individualized homeopathy), seem to confirm the finding that more rigorous trials have less-promising results. It seems, therefore, likely that our meta-analysis at least overestimated the effects of homeopathic treatments.

In 2001, a meta-analysis of clinical trials on the effectiveness of homeopathy concluded 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, a systematic review of publications suggested that mainstream journals had a publication bias against clinical trials showing positive results, and viceversa on the CAM journals, although it's probably an involuntary bias. A possible submission bias was also suggested, in which positive trials tend to be sent to CAM journals and negatives ones to mainstream journals. It also noted that the reviews on all journals approached the matter on an impartial manner, although most of the reviews on CAM journals avoided noting the lack of plausibility, unlike the ones on mainstream journals who almost always mentioned it.

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..

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. Their analysis concluded that there was "insufficient evidence to support clinical efficacy of homeopathic therapy in cancer care".

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."

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 .

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) homeopaths 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.

Regulation and prevalence

Homeopathy 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 public health service of several European countries, including France, the United Kingdom, Denmark, and Luxembourg. In other countries, such as Belgium, homeopathy is not covered. In Austria, the public health service 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 services have withdrawn this privilege. At the start of 2004, homeopathic medications, with some exceptions, were no longer covered by the German public health service, and in June 2005, the Swiss Government, after a 5-year trial, withdrew homeopathy and four other complementary treatments, stating that they did not meet efficacy and cost-effectiveness criteria, though insurance can be bought to cover such treatments provided by a medical doctor.

See also

• List of pseudosciences and pseudoscientific concepts
• List of homeopathic preparations
• Homeopathic dilutions

Notes and references

External links

Associations and regulatory bodies

• British Homeopathic Association (BHA)
• European Committee for Homeopathy (ECH)
• European Council for Classical Homeopathy (ECCH)
• National Center for Homeopathy (NCH)

Other links

• "UK Pharmacists urged to 'tell the truth' about homeopathic remedies". The Guardian, .
• Homeopathy: real medicine or empty promises?. US Food and Drug Administration. .
• Questions and answers about homeopathy. National Center for Complementary and Alternative Medicine (NCCAM). .National Institutes of Health Research Report
• Stephen Barrett HomeoWatch: Your skeptical guide to homeopathic history, theories, and current practices. .
• The scientific evidence on homeopathy. American Council on Science and Health. (2000). .
• Ameke Wilhelm, Drysdale AE (transl), Dudgeon RE (ed) (1885). History of homœopathy, with an appendix on the present state of University medicine. London: E. Gould & Son.
• James Randi Homeopathy Explained. . - Portion of 2001 Princeton lecture. (Complete 2 hr 10 min 43 sec lecture.)
• John Langone "Challenging the mainstream". Time Magazine, .
• Fisher Peter, Goldacre Ben Does homeopathy work?. . A debate on the evidence on both sides with Peter Fisher, Clinical Director of the Royal London Homeopathic Hospital and Ben Goldacre, medical writer and broadcaster.