Homeopathy/PreviousVersion

Homeopathy or homoeopathy—from the Greek hómoios (similar) and páthos (suffering)—is a system of alternative medicine based on the idea that substances known to cause particular combinations of symptoms in healthy people can also, in low and specially prepared doses, help to cure people whose disease has similar symptoms.

Homeopathy is used worldwide both by some medical doctors who use it as an alternative or a complement to conventional medical treatment for both acute and chronic ailments, by homeopathic practitioners in jurisdictions that require no medical training and by consumers who use it to treat common non-life-threatening acute conditions. Homeopathic medicines are widely recognized, often by custom rather than demonstrated efficacy, by individual governments and are usually sold without the need of a doctor's prescription even though homeopaths recommend that what they consider more potent not be used by Many health insurance companies provide coverage for homeopathic treatment as long as it is provided by a licensed medical doctor, although many refuse coverage of treatments they judge ineffective even when prescribed by a physician.

That said, the consensus of medical and scientific judgment is that homeopathy is unfounded. Although there are numerous studies that show the efficacy of homeopathic medicines, there has been little replication of these studies to truly verify efficacy beyond that of a placebo. Neither of the main homeopathic principles — similars and infinitisimals — makes sense to the critical scientific mind. The "principle of similars" appears to be merely an appeal to sympathetic magic, or at best an over-generalisation of a principle that actually applies in only a few cases. The "principle of infinitisimals" contradicts both common sense and scientific results; there is no proven mechanism to explain how the remedies might work, given that many of them are so dilute that they contain not a single molecule of the active ingredient. Homeopaths have rejoinders to each of these arguments and consider such statements to be evidence of medical arrogance; medical doctors consider homeopaths equally arrogant and there is little reason to believe that the two views will reconcile.

Principles of homeopathy, and their historical origins

There have been national and international homeopathic associations since the 19th century.

Homeopathic remedies are intended to stimulate the body's natural healing processes and invoke the "wisdom of the body". By selecting a medicine that has been found to cause in overdose in healthy people the similar symptoms the sick person is experiencing, this medicine is thought to mimic and augment the body's own defenses. Hygiene, diet, and various other natural therapies are also used by homeopaths in conjunction with the use of homeopathic medicines.

Two basic ideas in homeopathy are the principle of similars, sometimes stated as "like cures like", and the principle of infinitisimals, the idea that remedies become more potent if they undergo a specific pharmacological process called potentization. Potentization consists of repeated dilutions (1:10, 1:100, or 1:50,000) with vigorous shaking in-between each dilution, called succusion.

Individualization of treatment is also essential to the practice of classical homeopathy, whereby a medicine is chosen based on the person's oveall body-mind syndrome of symptoms, not just a generic disease diagnosis.

History

The early Greek physician Hippocrates of Cos (c. 450 BCE - 380 BCE), who is considered to be the "father of medicine", is also claimed by homeopaths as a pioneer in their own tradition — because he taught that "Natural forces within us are the true healers of disease," and because he thought that some diseases could be cured by the same things that caused them.

The principles of homeopathy were first methodically set out by a German physician, Samuel Hahnemann (1755–1843), who observed that a medicine sometimes evoked symptoms similar to those of the illness for which it was prescribed. In homeopathic theory, every person has a "vital force", with the power to promote healing and/or maintain good health. In this theory, the signs and symptoms of a disease reflect efforts of the body to defend itself against infection, environmental assault, or various stresses. Homeopathic treatment attempts to strengthen the "vital force" with remedies chosen for their ability (in large doses) to provoke the similar symptoms that the remedy is intended to heal.

In the early 18th century, the conventional medicine of the day was referred to as heroic medicine because its physicians often used large doses of toxic compounds in a seemingly valiant effort to save lives. Invasive procedures such as bloodletting and leeching were used indiscriminately, though, ironically, doctors who did not use these practices regularly were considered "quacks" and "charlatans." In 1783, disillusioned with "heroic" medicine, Hahnemann gave up his medical practice and devoted himself to translating medical books. Among them was the Treatise on Materia Medica by William Cullen, the leading physician of the 18th century. Cullen had written that cinchona bark (which contains quinine) was effective in treating malaria because of its bitter and astringent properties. Hahnemann questioned this, because he knew that other substances were as bitter and astringent, but had no therapeutic value in this disease.

Hahnemann observed that the effects he experienced from ingesting cinchona bark were similar to the symptoms of malaria. He observed similar results with other substances, and so conceived of the law of similars, or "let like be cured by like" (Latin: similia similibus curentur). This is the assertion that a disease can be cured by remedies that (in macroscopic, milligram doses) produce the same symptoms as those of the disease, and is a guiding principle in homeopathy. Hahnemann believed that, by inducing symptoms similar to the disease, the natural healing processes of the body would be stimulated enough to neutralise the disease. From these ideas, he developed a new system of health care, which he named "homoeopathy" (meaning "like disease") - and coined the term "allopathy" ("different than disease") to refer to the conventional medicine of the day (heroic medicine).

For the first two decades, Hahnemann used "crude" doses of medicinal substances ("crude", in homeopathic use, means doses that still contain some of the original ingredient). He strove to find the lowest doses at which his remedies would still be effective, and he concluded that his remedies worked better the more he diluted them as long as he “potentized” them, i.e. serial dilution followed by vigorous shaking (succussion). Homeopathy thus became inextricably linked with ultradilution—repeated dilution of substances - followed by succussion. Hahnemann had no clear explanation as to how or why these potentized remedies might have benefits; he distrusted theoretical explanations and argued that all that mattered was whether a treatment was therapeutically effective.. By the late 18th century, Hahnemann had coupled his theory with a method of "provings" to determine what symptoms a substance causes and thereby what a particular medicine might cure (see below).

The first homeopathic school in the U.S.A. opened 1835, and in 1844, the first U.S. national medical association - the American Institute of Homeopathy - was established. By the end of the 19th century, 8% of American medical practitioners were homeopaths, and there were 20 homeopathic colleges and more than 100 homeopathic hospitals in the U.S.A. One reason for the growing popularity of homeopathy was its relative success in combatting the epidemics that raged at the time. Cholera, scarlet fever, typhoid fever, and yellow fever killed many people, but death rates in hospitals that used heroic medicine were typically two- to eight-fold higher than in homeopathic hospitals.

In the early 20th century, the "Flexner Report" triggered major changes in American medical education. Many medical schools and colleges, including those teaching homeopathy were closed down, while others became devoted to a new vision of a biochemical understanding of medicine that replaced the discredited heroic medicine. Nevertheless, in the 1960's, the popularity of homeopathy began to revive in the U.S.A, and a 1999 survey reported that over 6 million Americans had used homeopathy in the previous 12 months.

Conflict with conventional medicine

The theory underlying homeopathy is not considered plausible by most academic scientists in Europe and the U.S.A., and the treatment advice offered by homeopaths is in disagreement with conventional medicine. Their view is that homeopathy exploits the placebo effect - i.e. that the only benefits are those induced by the power of suggestion, by arousing hope, and by alleviating anxiety. Placebos have played a large part in conventional medicine since their first deliberate use by William Cullen in the 18th century.

"...we all recognise the strong placebo effect in, probably, all aspects of medical treatment, whether they are conventional or not" - Professor Tom Mead

Cullen used regular drugs as placebos, but at much lower doses than he expected to be effective, and "to comfort and please the patient" rather than with any hope of a specific effect.. Many modern physicians consider it unethical to mislead their patients; while homeopaths who invoke the Hippocratic tradition assert that it is unethical to not use safer therapies first in the treatment of sick people, except in medical emergencies.

Homeopaths believe that the fundamental causes of disease are internal and constitutional and that infectious disease is not just the result of infection but also of susceptibility. This respect for host resistance leads them to avoid conventional treatments that suppress symptoms. Physicians consider that most diseases are caused by a combination of external causes (such as viruses, bacteria, toxins, dietary deficiency, physical injury) and physiological dysfunction (including genetic defects and mutations such as those which trigger cancers). The main goal of conventional medicine is to eliminate these causes, although physicians often also use drugs to suppress the symptoms of a disease (to alleviate the pain, injury, and distress that they cause).

Whereas homeopaths emphasize that they provide remedies tailored to the individual patient, conventional medicine focuses on treatments that have been demonstrated (in randomised clinical trials)to be effective when given in a standard form to many patients with a given disease. Clinical trials also seek to identify subgroups of patients (identifiable by age, gender, comorbidities etc.) that are "responders" or "non responders" to a treatment, to provide a rational basis for individualization of treatments. Physicians have access to a very large repertoire of prescription drugs for this purpose (11,706 in the U.S. Food and Drug Administration Approved Drug Products with Therapeutic Equivalence Evaluations 26th Edition Electronic Orange Book (EOB)4 ) , a repertoire that is constantly changing as less effective drugs are replaced by better drugs.

Homeopathic response

Homeopaths claim that the overall body of evidence drawing from clinical trials, basic science studies, outcome trials, cost-effectiveness studies, epidemiological reviews, and case studies of people with extreme illness show biological action and clinical efficacy from homeopathic medicines. Homeopaths also claim that many of the studies in which homeopathy appears no more effective than a placebo are methodologically flawed — they either did not follow proper homeopathic procedure in the selection of remedies to sick subjects or they did not utilize adequate repetition of the medicine.

Homeopaths point to a long safety record for their medicines and even those skeptical of their claims do not doubt the safety of those remedies – an inert substance is not going to harm anyone. The concern is that people who use homeopathy as an alternative to medical care take additional risk when they forego conventional treatment for serious illness such as anti-inflammatories and bronchodilators for asthma, or do not receive established preventive treatments, such as vaccines or anti-malarial drugs. Homeopaths assert that patients face much greater risk in using conventional drugs as a first method of treatment and seek to remind patients and physicians of the wise words of Hippocrates who proclaimed, "First, do no harm."

Prophylactic use of homeopathy

Some homeopaths believe that their treatments can prevent disease, a notion known as "'homeoprophylaxis". Homeoprophylaxis has not received support from repeated trials and has no place in conventional medicine.

Homeopathic organizations including the UK's Faculty for Homeopathy have condemned use of homeopathic remedies in place of conventional travel vaccinations and anti-malarial drugs. Despite this, an undercover investigation by BBC Newsnight uncovered a large number of high street homeopaths willing to prescribe homeopathy instead of anti-malarials.

In 2010, the Cuban government sponsored a very large study of 2.4 million Cubans that showed a substantial benefit in preventing leptospirosis. A critic of the paper has stated it has methodological flaws, namely unsuitable control.

Homeopathic "provings"

Homeopathic practitioners determine the therapeutic indications for their remedies from provings, in which volunteers are given repeated doses of substances (usually in single-blind or double-blind protocols), and keep a diary of any apparent symptoms. The effects are recorded in textbooks, called Materia Medica and Repertory, or nowadays in expert system software. Homeopathic provings provide the basis to determine what a substance causes in overdose and thereby what it is thought to cure. The symptom complexes that these substances cause are used to compare with a patient's symptoms in order to select, as the appropriate most similar remedy, the substance whose effects are closest to the patient's symptoms—called the "simillimum". Homeopaths prescribe a remedy (in potentized doses) when a sick person has a syndrome of symptoms that resembles the syndrome of symptoms that it causes in drug proving.

In 2006, the U.K.’s licensing body, the Medicine and Healthcare Products Regulatory Agency, altered their regulations to permit homeopathic remedies to be advertised using provings to support their claims (justifying phrasing such as “For the relief of...”. This elicited protests from scientists, who called it a departure from the principle that such claims should be justified by evidence of efficacy.

Homeopathic remedies

In the U.S.A., the Homœopathic Pharmacopœia of the United States is a handbook that describes how to manufacture homeopathic remedies, and which is approved by the Food and Drug Administration (FDA), the governmental agency that regulates drugs. Remedies listed in the HPUS are defined as "homeopathic drugs", which grants them a different standard of regulation than conventional drugs. Manufacturers of homeopathic remedies do not have to submit new drug applications to the FDA, and their products are exempt from good manufacturing practice requirements related to expiration dating, and from finished product testing for identity and strength. Remedies in solid oral dosage form must have an imprint that identifies the manufacturer and which indicates that it is homeopathic.

In 1938, the federal Food, Drug, and Cosmetic Act, sponsored by New York Senator Royal Copeland, a former homeopathic medical school dean, gave the FDA the power to regulate drugs and granted legal recognition to the HPUS. Conventional medicines for which a New Drug Application is required must be accompanied by approved evidence of safety and efficacy. In contrast, any substance can become a homeopathic remedy if "provings" are first conducted to determine what it causes in overdose and therefore, according to homeopathic theory, what it can cure in potentized doses. Today, homeopaths use about 3,000 remedies, made from plants, trees, and fungi and from a wide variety of mineral and animal sources. Even some unusual substances, called imponderables, are made into remedies, including electricity, X-ray, and magnetic north and south poles. By convention, the first letter of the Latin-derived name of a remedy is capitalized. When the source is well-defined, the traditional name rather than chemical, International Nonproprietary Name or biological nomenclature, is preferred, such as Natrum muriaticum rather than sodium chloride.

Remedies are available in several forms (single medicine, homeopathic formula or complex medicines, and some for external application). Remedies for internal consumption come either in pill form or as liquid. Most do not require a doctor's prescription, unless the dosage is in a non-potentized or low potency dose and if the original substance is potentially toxic (in Europe, a substance must be diluted at least 1:1000 to be deemed homeopathic). In the U.S.A., if a remedy is claimed to treat a serious disease such as cancer, it can be sold only by prescription. Only remedies for “self-limiting conditions”—colds, coughs, fever, headaches, and other minor health problems that are expected to go away on their own—can be sold without a prescription.

The most characteristic principle of homeopathy is that the efficacy of a remedy can be enhanced by "dynamization" or "potentization". In this process, liquids are diluted (with water or ethanol) and shaken by ten hard strikes against an elastic body ("succussion"), to get the next, higher, potency. When insoluble solids such as oyster shell are used for remedies, they are diluted by grinding them with lactose ("trituration"). The original dilutions by Hahnemann used a 1 part in 100 (centesimal; "C" potencies), or 1 part in 50,000 (quintamillesimal; "LM" or "L" potencies). Dr Constantine Hering later introduced the Decimal potencies ("D" or "X" potencies). The dilution factor at each stage is 1:100 ("C" potencies), 1:50,000 ("LM" potencies) or 1:10 ("D" or "X" potencies); Hahnemann advocated $30C$ dilutions for most purposes (i.e. dilution by a factor of 100³⁰ = 10⁶⁰). It is extremely unlikely that even one molecule of the original substance would be present in a $30C$ dilution. Thus, liquid remedies of a high "potency"' contain just water, but according to homeopaths, the structure of the water has been altered (see memory of water); remedies in pill form contain just sugar.

Many homeopathic remedies sold in health food stores and pharmacies are "low potencies," that is, doses that are 3X, 3C, 6X, 6C, 12X, and 12C, all of which, except the last dose, have material doses of the original substances in the medicine.

Homeopathy in practice

Many famous people over the past 200 years have been users and advocates of homeopathy, and it is an important thread in the history of medicine. Its growth in the 19th century influenced how conventional medicine organised and how it came to formulate its present vision of evidence-based medicine, in contrast to practice based on individual clinical experience. Homeopathic remedies are used throughout the world, and homeopathy generally scores highly in "patient satisfaction" surveys. In the U.K., a survey cited by the British Homeopathic Association found that 15% of the public "trust" homeopathy. It found even more trust in homeopathy in other countries: 58% Brazil, 53% Chile, 49% Saudi Arabia, 40% France, 28% Russia, 27% Germany, and 18% USA. That said, patient satisfaction and strength of public support for a treatment does not count as scientific evidence—just because a lot of people believe something to work does not make it work (see argumentum ad populum).

In some countries, homeopathic remedies are sold over-the-counter in both pharmacies and health food or other retail outlets for self-treatment of common self-limiting ailments and injuries; the global self-medication market is estimated at 48.2 billion dollars (13.4% of the world pharmaceuticals market), of which sales of homeopathic remedies account for 0.3%. . Some medical doctors in Europe, also occasionally prescribe homeopathic remedies for a variety of mainly self-limiting conditions. In India, homeopathy has more than 200,000 registered practitioners and is recognised as one of the Indian "National Systems of Medicine" under the Department of AYUSH (Ayurveda, Yoga and Naturopathy, Unani, Siddha and Homeopathy). About 10% of the Indian population depends solely on homeopathy for their health care needs. In India, it is illegal to practice as a homeopath without a license and professional qualifications.

Some countries allow homeopaths to describe themselves in equivalent ways to doctors, with a system of qualification and oversight, but there are no universal standards for homeopathic education. In some countries, all (or virtually all) professionals that prescribe homeopathic remedies are MDs (such as France, Spain, Argentina, Colombia). Some countries have exclusively homeopathic medical schools (India, Pakistan, Mexico etc.), some have naturopathic medicine colleges in which students are taught homeopathy as part of their curriculum (Germany has its "heilpraktica"/health practitioners; the U.S.A., Canada, and Australia have naturopathic medicine schools that include homeopathy), and some countries certify "professional homeopaths" who have attended homeopathic schools and who then pass independent examinations that grant "certification" as homeopaths. In the U.S.A., there is also a separate certification process available only to MDs and DOs (there are similar choices of certification available in the U.K. for medical doctors, who've done at least MBBS). Also in the U.S.A., naturopathic physicians have their own homeopathic certifying agency. The American Homeopathic Pharmaceutical Association, estimated the 1995 retail sales of homeopathic remedies in the U.S.A. at $201 million and growing at 20% per year; the number of homeopathic practitioners in the U.S.A. increased from fewer than 200 in the 1970's to about 3,000 in 1996.

In Europe, homeopathic remedies are occasionally prescribed by MDs (often as placebos), including by 30-40% of French and 20% of German doctors. Some of this s covered by public funds; in France, 35% of the costs of homeopathic remedies prescribed by an MD are reimbursed from health insurance. In the U.K., five homeopathic hospitals are funded by the National Health Service (NHS) and homeopathic remedies are sold over the counter. In 2007, the over-the-counter market in homeopathy was around £40million in the U.K. ; the total over-the-counter market was £1.2 billion in 1994. Family doctors in the U.K. issued 796 million prescriptions in 2007, of which 49,300 were for homeopathic remedies, down from 83,000 in 2005. In 2008, it was reported that the NHS was progressively withdrawing funding for homeopathic treatments because of doubts about their efficacy . Of 248,000 registered practitioners of medicine in the U.K., about 400 are members of the Faculty of Homeopathy. However, in the U.K., anyone can declare themselves to be a homeopath and practice without any qualification ("common law" that allows freedom of choice in medical care in England has a long history)

In France and Denmark, licenses are required to diagnose any illness or to dispense any product whose purpose is to treat illness. In many countries, there are no specific legal regulations concerning homeopathy. In Austria, the public health service generally requires proof of effectiveness to reimburse medical treatments, but makes an exception for homeopathy. Almost 70% of all over-the-counter homeopathic remedies are sold in Western Europe. France is the largest market for homeopathic remedies in the world, worth over 300 million euros in 2003 (in a total over-the-counter drug market of over 770 billion euros), followed by Germany (200 million euros).

A typical homeopathic visit

Homeopaths view illness as a systemic condition, a disturbance in the overall homeostasis of the total being and accordingly, consider that almost any sick person, may benefit from proper homeopathic treatment.

"homeopathy is designed to treat the whole person and can therefore be considered in almost any situation where a person's health is depleted."

As the American Institute of Homeopathy puts it in their "Standards of Practice": "The physician must remember that he is treating a patient who has some disorder; he is not prescribing for a disease entity." .

Patients often come to homeopaths with chronic problems that have not responded to conventional treatment. Some common ailments for which patients seek homeopathic care are eczema, chronic fatigue syndrome, asthma, migraine, irritable bowel syndrome, allergic disorders, arthritis, fibromyalgia, hypertension, Crohn's disease, premenstrual syndrome, rhinitis, anxiety and depression, but they also treat patients with serious diseases, including multiple sclerosis, chronic obstructive pulmonary disease, and cancer. and AIDS For gangrene, for example, homeopathic remedies are prescribed in the belief that they will strengthen a person's defenses and to initiate healing; a very different approach than medical therapy. Some of many homeopathic remedies for gangrene include Arsenicum Album, Secale (from rye/ergot), and Carbo vegetabilis (from charcoal).

When a homeopath is conducting an interview to characterise a patient's syndrome of symptoms, some "categories of change" are identified as important: (1) emotion (2) mentation (3) specific physical functioning (4) general physical changes (5) perception of self (6) relationships (7) spirituality (8) lifestyle (9) energy (10) dream content and tone (11) well-being (12) perceptions by others (13) life relationships (14) a sense of freedom or feeling less "stuck" (15) sleep (16) coping (17) ability to adapt (18) creativity (19) recall of past experiences

In "Classical homeopathy" or "Hahnemannian homeopathy", a single remedy is chosen according to the physical, emotional, and mental symptoms that the sick individual is experiencing rather than only the diagnosis of a disease. ("Commercial" or "user-friendly" homeopathy refers to the use of a mixture of remedies in a formula containing individual ingredients chosen by the manufacturer for treating specific ailments.) When deciding which remedy to prescribe, classical homeopaths place emphasis on the patient's unique symptoms and their psychological state. They gather this information from an interview, typically lasting from 15 minutes to two hours, with one or more follow-up consultations of 15 to 45 minutes. They assess how the patient experiences their disease—i.e. they give priority to the overall syndrome of symptoms and the unique and idiosyncratic symptoms, in contract to the conventional medical approach of trying to identify the causes of the disease. Their goal is to determine factors that might predispose the patient to disease, and find a treatment that will strengthen that patient's "overall constitution". After the interview, the homeopath consults the references described in the table on the right. Some homeopaths make quick prescriptions based on "keynotes"—the highlights of the best known characteristics of a remedy. The real challenge of homeopathic practice, though, is to find the remedy that best matches the patient's syndrome of physical and/or psychological symptoms—the "similimum". Homeopathy rejects the conventional medical concept of treatments that target mechanisms of disease, and instead uses remedies that target syndromes of symptoms. Some homeopathic protocols look like the following:

1. A physician qualified in both homeopathy and conventional medicine, after diagnosing a chronic condition that does not indicate the need for medical urgency, might prescribe a homeopathic remedy rather than a conventional drug which he feels may be ineffective and/or likely to have side effects. Most physicians, however, are not homeopathically trained, and most homeopaths are not medically qualified.
2. Homeopaths recognize that trauma might require conventional medical attention but may complement the conventional treatment with homeopathy.
3. Homeopaths disagree with conventional medicine about the role of immunization and chemoprophylaxis for infectious diseases and prefer to prescribe remedies that they believe will strengthen a person's immune and defense system.
4. For some disease conditions, such as asthma and acute bronchitis, homeopathic remedies are often prescribed not only to alleviate chronic symptoms, but also to treat acute attacks. Remedies might also be used after an asthmatic episode with the intent to prevent recurrences.

The homeopathic treatment of acute problems does not need the same depth or breadth of interview as chronic conditions. According to homeopaths, because the symptoms of a common cold or a headache or an allergy vary from person to person, each may need a different remedy. However, they believe that people who experience an injury generally have similar symptoms, so they think that some homeopathic remedies might be routinely useful in such cases.

Homeopaths who practice "classical homeopathy" prescribe one remedy at a time—a remedy that best fits the overall syndrome of the patient. The same remedy might thus be prescribed for patients with very different diseases; conversely, patients suffering from the same disease may be prescribed different remedies. For example, hay fever would be treated with any of several remedies, usually based on the specific symptoms, but sometimes on the etiology of the allergy. Some common remedies are: Allium cepa (onion, which causes tears to flow and a clear burning nasal discharge that irritates the nostrils), Euphrasia (eyebright, which causes a clear and bland nasal discharge along with tears that burn and irritate), Ambrosia (ragweed) and Solidago (goldenrod); ragweed and goldenrod are herbs whose pollen is aggravating to some hay fever sufferers. These remedies are commonly given during the acute symptoms of hay fever. At other times, a homeopath might treat these patients with a constitutional remedy based on the patient’s family history, health history, and overall physical and/or psychological state.

Attempts to provide a scientific foundation for homeopathy

Homeopathy arose when important concepts of modern chemistry and biology, such as molecules and germs, were understood poorly, if at all. In Hahnemann's day, many chemists believed that matter was infinitely divisible, so that it was meaningful to talk about dilution to any degree. The size of atoms was not calculated until 1865 (by Josef Loschmidt), but we now know that, for example, a teaspoon of seawater (roughly 5 ml) contains about 160 mg of NaCl. The molecular weight of NaCl is 58.4, and by Avogadro's number, , 58.4 g of NaCl (one mole) contains 6.02×10²³ molecules, so our teaspoon contains about 2×10²¹ molecules of NaCl. A 12C dilution of seawater will have about one molecule of NaCl per litre. Thus remedies diluted to more than about 12C are virtually certain to contain not a single molecule of the initial substance. This is recognized by advocates of homeopathy, who assert that the healing power is not in the action of molecules, but perhaps in some way that the water itself has been changed - the presumed "memory of water".

Widely differing (and mutually inconsistent) explanations are proposed for this alleged memory. For instance, homeopaths point out that water is not simply a collection of molecules of H₂O, but contain isotopologues (molecules with different isotopic compositions such as HDO, D₂O and H₂¹⁸O). Mass spectroscopy can detect these different isotopologues, but the concentration ratios can only be changed by nuclear reactions - they are not affected by homeopathic treatment, so their presence cannot explain its "memory". The fact that the molecules H₂O appear in two proton-spin forms (ortho and para) has also been suggested as a possible source of memory of water. These two spin forms, which appear in a ratio 3:1, are chemically non-distinguishable and are very difficult to separate or to convert into each other, so it is highly unlikely that a homeopathic treatment could change this ratio. Even if homeopathic tinctures could give somehow rise to ortho:para ratios other than 3:1, it requires a massive leap of imagination to envisage how changes in these ratios could result in different, specific healing qualities.

Some homeopaths believe that successive shaking might lead to "clustering" of water molecules. This contradicts current scientific understanding that motions in liquid water are on the picosecond (10⁻¹² second) timescale and that such clusters could not live longer than a few picoseconds. Another suggestion is that double-distilled and deionized water contains trace amounts of contaminating ions: water, after vigorous shaking, might include dissolved atmospheric gases in the form of nanobubbles, molecular ions produced from water reacting with airborne contaminants, and silicates—tiny glass "chips"; it's easy to see that such contamination is very likely to occur, but hard to see how it could have specific therapeutic value In 2009, Luc Montagnier, the Nobel Laureate virologist, claimed that the DNA of pathogenic bacteria and viruses massively dissolved in water emit radio waves. This, he claimed, can also be used to detect the medicine in a homeopathic remedy. The claim has been received with deep skepticism by the scientific community..

Homeopaths contend that the "principle of similars" is analagous to the cocept of hormesis and is the basis for vaccination and allergy desensitation, two methods in modern medicine that augment immune response to either prevent or treat disease, while physicians assert that these treatments are not based on any homeopathic principle but on specific immunological and allergy research. Scientists and medical doctors today do not think that this law is generally true or useful, and they explain the efficacy of vaccination without referring to it. Although homeopathic remedies and vaccinations both use low doses of ingedients, the doses in remedies are very much lower than those in vaccines. Vaccines produce a measurable immune response (e.g., immunoglobulin production); homeopathic remedies do not. Thus conventional treatments involve measurable doses of substances, at levels known to activate a cellular response. In contrast, homeopathic remedies above the $24X$ ($12C$) potencies do not contain enough molecules to activate any known metabolic or signalling pathway.

In brief, for homeopathy to receive serious scientific consideration, there must be plausible explanations for the following:

• how the process of manufacturing a homeopathic remedy could yield a biologically active substance
• why the principle of similars might apply in the case of homeopathic remedies
• how a biological mechanism could have evolved to recognize the specific nature of homeopathic remedies

There also needs to be compelling evidence for the efficacy of homeopathic remedies, evidence that cannot be explained by placebo effects. These stringent demands are often summarised by the maxim "Extraordinary claims require extraordinary proof".

Homeopaths complain that they are up against a double standard in medicine and science. They point out that there is a long history of conventional medical treatments that have been used long before any knowledge of their mechanism of action. Only relatively recently, for instance, has it been understood how aspirin works, but medical standards of evidence grow more strict. It is much less likely that a clinical trial will be approved, of a new medical drug, unless there is substantial knowledge of a plausible mechanism. In the U.S., homeopathic remedies are exempt from the clinical trial requirement.

Safety and efficacy

In conventional medicine (see New Drug Application), the basic phases of evaluating a drug determine: if it causes dangerous effects in healthy volunteers; if it is adequately present in the body to achieve an effect; and if it is more effective than established treatments. Randomized controlled trials use statistical analysis of large groups of patients to determine whether a treatment given in a standardised form to one subgroup is safer and more effective than a different standardised treatment given to another. This conflicts with an approach that believes that treatments must be individually tailored to each patient. Clinical trial specialists have proposed protocols to test "low responding" or individualized therapies in statistically valid clinical trials. For homeopathy, by having a group of people who identify as ill and asking a qualified homeopath to diagnose them - then having a remedy given to a subset of them, and medicines that share the same physical properties but are homeopathically inert (for instance, by using ordinary water rather than homeopathically diluted water in preparing the substance). This method thus tests the standard diagnostic method as the experimental treatment, rather than the specific medications. There have not been, however, many homeopathic trials using this method.

Clinical trials

Homeopaths assert that trials of efficacy, basic sciences research, historical usage of homeopathic medicines in the treatment of people in various infectious disease epidemics and cost-effectiveness studies provide reasonable evidence for the benefits of homeopathy. Generally, natural scientists and medical doctors doubt that homeopathic treatments have any efficacy. They regard the evidence in support of efficacy as extremely weak, and point out that the claims made regarding homeopathy's underlying mechanism require an extraordinary level of proof to overcome their inherent impplausibility.

The "balance of evidence" as to whether homeopathy has any effects other than placebo effects depends on who is balancing the evidence. Homeopaths favour the evidence of their own experience in treating patients, supported by the satisfaction reported by their patients in surveys; they also state that most published trials have shown some beneficial effects, including for postoperative ileus , allergic rhinitis , and for individualised treatment of childhood diarrhoea Other meta-analyses suggest that homeopathic remedies are no different to placebos The Cochrane Collaboration publishes meta-analyses of trial results, and none of their analyses of homeopathy indicate any significant benefit.

A 1991 global meta-analysis in the British Medical Journal of 105 homeopathic trials, 81 with positive outcomes, concluded that "At the moment the evidence of clinical trials is positive but not sufficient to draw definitive conclusions because most trials are of low methodological quality and because of the unknown role of publication bias."; they stated that "we would be ready to accept that homoeopathy can be efficacious, if only the mechanism of action were more plausible A 1997 meta-analysis in the Lancet similarly concluded that the results "were not compatible with the hypothesis that the effects of homoeopathy are completely due to placebo." However, larger high-quality trials have tended to show little or no significant effects, as later concluded by the authors of theLancet study In the U.K., the NHS recognizes that there have been about 200 randomised controlled trials evaluating homeopathy; some show efficacy and some don't. They conclude, "Despite the available research, it has proven difficult to produce clear clinical evidence that homeopathy works". Homeopaths believe that such attitudes reflect bias, and that because homeopathy does not lend itself to controlled trials, those with a negative outcome may be false negatives.

According to critics, trials of homeopathy have been mostly small and flawed in design and/or reporting, with poor measuring techniques and difficulties in replicating results. Why small trials should have more strongly positive outcomes than large trials is generally attributed to "publication bias" – the tendency of trials to be reported only if the outcome is positive; many small trials with negative or inconclusive outcomes go unreported because they are thought to be uninteresting. Conversely, homeopaths argue that most of the larger high-quality trials tested a single homeopathic remedy, without the appropriate individualization of treatment.

In 1999, the Government of Switzerland, for 5 years, allowed costs for treatment with homeopathy and four other CAM modalities to be reimbursed under the country’s health insurance scheme, and set out to evaluate their cost-effectiveness (the Complementary Medicine Evaluation Programme (Programm Evaluation Komplementärmedizin, PEK). A team of scientists and practitioners, including a homeopath, conducted a meta-analysis that became the single most cited study of homeopathy, arousing considerable media attention and a storm of protest from homeopaths. The study, published in the Lancet by Shang et al. took a novel approach; whereas traditional meta-analyses combine studies of a single, given condition, this was a "global" meta-analysis testing the hypothesis that all effects of homeopathy are placebo effects. If so, the authors reasoned, then the predominance of positive homeopathy trial reports reflects publication bias, and hence the magnitude of effects should diminish with sample size and study quality. They analyzed 110 placebo-controlled homoeopathy trials and 110 matched conventional-medicine trials. In both, effect size declined with improved study quality; however, some effect was still present in the largest and best conventional medicine trials, but not in the largest and best homeopathy trials. The authors concluded that homeopathy was no better than placebo, and suggested that no further research on homeopathy is necessary. The article was accompanied by an unsigned editorial titled “The end of homeopathy”" and another, signed, editorial . The Lancet subsequently published critical correspondence, and received an open letter from the Swiss Association of Homoeopathic Physicians (SVHA). which declared:

“The meta-analysis may be statistically correct. But its validity and practical significance can be seen at a glance: not one single qualified homoeopath would ever treat one single patient in clinical practice as presented in any of the 110 analysed trials! The study cannot give the slightest evidence against homoeopathy because it does not measure real individual (classical) homoeopathy. It confounds real homoeopathic practice with distorted study forms violating even basic homeopathic rules.”

Critics of the Shang et al. analysis noted that several studies defined as "high quality" by Linde et al. (1997) were not defined by high quality by Shang et al.,and most of these showed a positive effect of homeopathic treatment. The Shang et al. analysis also excluded a relatively large study of chronic polyarthritis (N=176) because no matching trial could be found. An article in the Journal of Clinical Epidemiology stated "This result can be interpreted differently. Following Shang's perspective it can be explained by small study bias (which includes publication bias). In contrast, one may hypothesize that Shang's result is falsely negative." The authors noted that four of the 21 best trials selected by Shang et al. dealt with preventing or treating muscle soreness; these found no benefits to homeopathy, but the remaining 17 trials show an overall significant effect, mainly determined by two trials on influenza-like diseases. Thus, they argue, it is possible that homeopathy might be effective for some conditions and not others.

Safety

The highest ideal of cure is the speedy, gentle, and enduring restoration of health by the most trustworthy and least harmful way (Samuel Hahnemann)

In the U.S.A., the Food and Drug Administration determines what dose is safe for over-the-counter sale, and its view is that there is no real concern about the safety of homeopathic remedies because of the extremely small dosages, and that the vast majority are over-the-counter drugs that do not need a doctor's prescription. In the U.S.A., homeopathic remedies must have at least one indication for usage for a disease or condition that is self-limiting and that does not require medical diagnosis or medical monitoring. The European Union allows homeopathic medicinal products, if they are at least 3X, that is, they may not contain either more than one part per 10,000 of the mother tincture or more than 1/100th of the smallest dose of an active substance. No specific therapeutic indication may be given on the label of the product. Some physicians, however, maintain that homeopathic treatment is relatively unsafe, because it might delay other treatment/s, if it fails to work. Homeopaths respond by claiming that using homeopathic remedies can delay or reduce the use of conventional medicines that are ineffective and dangerous.

Probably every modern pharmacologist would agree with Hahnemann that most drugs of the 19th century were at best ineffective and often dangerous. However, some homeopaths question whether modern drugs are safe and effective, and recommend homeopathic remedies instead. A 2006 survey by the U.K. charity Sense About Science revealed that homeopaths were advising travelers against taking conventional antimalarial drugs, instead recommending a homeopathic remedy. Even the director of the the Royal London Homeopathic Hospital condemned this:

I'm very angry about it because people are going to get malaria - there is absolutely no reason to think that homeopathy works to prevent malaria and you won't find that in any textbook or journal of homeopathy so people will get malaria, people may even die of malaria if they follow this advice.

Another concern is that many homeopaths think that vaccination for common diseases, such as measles and chicken-pox, is unnecessary, and even that vaccines can be damaging to health, because of the mercury and aluminum in them, because the bacterium or virus in the vaccine may neither be dead nor weak enough, and/or because some childhood infectious diseases may strengthen immune responsiveness. Such advice is considered irresponsible by public health professionals, who assess the benefits of vaccination as vastly outweighing the risks. Measles is not a major killer in the western world, where most children are vaccinated at about two years old. However, in 1999 there were 875,000 deaths from measles worldwide, mostly in Africa. In 2001, a "Measles Initiative" was initiated involving the American Red Cross, UNICEF and the World Health Organization, By 2005 more than 360 million children had been vaccinated, and the death toll had dropped to 345,000. Adult herpes zoster infection is a reactivation of childhood chickenpox, affects 1 in 3 adults, and can cause chronic, severe nerve pain (postherpetic neuralgia} in 10-18% of cases, and eye involvement in 10-25%. Chickenpox immunization prevents this; a herpes zoster vaccine is now recommended for all adults 60 years and older.

Homeopaths discourage the public from using homeopathic high potency remedies (the 200th potency and higher) unless the person is adequately trained in homeopathy. They advise that repeated doses of high potency remedies can lead the person to experience a "drug proving," a situation in which the person experiences symptoms akin to an overdose (the apparent symptoms are said to resolve themselves shortly after the person stops taking the remedy).

Government and institutional assessments

In the United Kingdom, the House of Commons Science and Technology Committee produced a report in 2010 on the evidence for homeopathy with reference to its use in the NHS. It concluded that the principle of "like-cures-like" is "theoretically weak" and "fails to provide a credible physiological mode of action for homeopathic products. We note that this is the settled view of medical science." The report also expresses considerable doubt as to the effectiveness of ultra-dilution in homeopathy and describes it as "scientifically implausible". It found that there was no good evidence of effectiveness of homeopathy:

In our view, the systematic reviews and meta-analyses conclusively demonstrate that homeopathic products perform no better than placebos.

The report rejected evidence presented by the British Homeopathic Association on systematic reviews and accepted Professor Edzard Ernst's account of the failings in the systematic reviews and other evidence presented by the BHA. It stated that advocates of homeopathy had chosen "to rely on, and promulgate selective approaches to the evidence base". It also rejected calls for further research:

There has been enough testing of homeopathy and plenty of evidence showing that it is not efficacious. Competition for research funding is fierce and we cannot see how further research on the efficacy of homeopathy is justified in the face of competing priorities.

It recommended against the use of homeopathy on the NHS because of the ethical problems in prescribing a placebo (as they concluded homeopathy to be): in particular, for a placebo to be effective, the patient must not know it is a placebo, but medical ethics requires that a patient must be able to make an informed choice. It also advised that, if the NHS appears to endorse homeopathy, there is a danger that patients will neglect conventional medicine, with potentially serious health consequences. The report concludes that homeopathy should not be funded by the NHS, that funding of homeopathic hospitals should not continue and that NHS doctors should not refer patients to homeopaths.

The report conclusions have been supported by the British Medical Association. The Royal Pharmaceutical Society of Great Britain suggested that patients ought to be "made aware of the fact that there is no scientific basis for the use of homeopathy", and that unless homeopathy can be shown to be efficacious "using appropriate methodology (as for conventional medicines)" any "claims of efficacy should be removed from the label". It also concluded that "homeopathic remedies should be reviewed by NICE if they are to be used within the NHS to ensure that they give value for money" – historically, homeopathy has not been subject to review by NICE. The British Government has decided to continue funding homeopathy (at a very low level) on the NHS.

Medical organizations' attitudes

The American Medical Association (AMA) was founded in 1847, and from the 1860s to the early 20th century, its ethical code forbade its members to consult with MDs who practiced homeopathy. Today, the AMA is not overtly antagonistic to homeopathy, but their current policy states: "There is little evidence to confirm the safety or efficacy of most alternative therapies. Much of the information currently known about these therapies makes it clear that many have not been shown to be efficacious."

To join the previously cited American Institute of Homeopathy today, one must have a mainstream medical license (MD, DO, DDS), and, in addition, homeopathic training.

In the U.K., some homeopathic treatment is available on the NHS. The NHS funds homeopathic hospitals in Glasgow, Liverpool, Bristol and London and there are several NHS homeopathic clinics in Scotland, treating approximately 55,000 patients per year by some 600 doctors. In 2010 the British Medical Association voted in favour of stopping any use of NHS funds for homeopathy, and proposed that pharmacists should remove homeopathic remedies from their shelves to prevent them from being confused with medicines. However, the British health minister declared that doctors should be free to decide whatever treatment they think appropriate in individual cases, and so homeopathic care remains a (very small) part of the NHS.

In the U.S.A.,The National Center for Complementary and Alternative Medicine (NCCAM) administers public-funded research into alternative medicine . Their 2003 report on homeopathy (here) asks: "Are there scientific controversies associated with homeopathy?", and replies: "Yes. Homeopathy is an area of complementary and alternative medicine (CAM) that has seen high levels of controversy and debate, largely because a number of its key concepts do not follow the laws of science (particularly chemistry and physics). It is debated how something that causes illness might also cure it. It has been questioned whether a remedy with a very tiny amount (perhaps not even one molecule) of active ingredient could have a biological effect, beneficial or otherwise. There have been some research studies published on the use of ultra-high dilutions (UHDs) of substances, diluted to levels compatible with those in homeopathy and shaken hard at each step of dilution. The results are claimed to involve phenomena at the molecular level and beyond, such as the structure of water, and waves and fields. Both laboratory research and clinical trials have been published. There have been mixed results in attempts to replicate them. Reviews have not found UHD results to be definitive or compelling. There have been some studies that found effects of UHDs on isolated organs, plants, and animals. There have been controversy and debate about these findings as well. Effects in homeopathy might be due to the placebo or other non-specific effect. There are key questions about homeopathy that are yet to be subjected to studies that are well-designed--such as whether it actually works for some of the diseases or medical conditions for which it is used, and if so, how it might work. There is a point of view that homeopathy does work, but that modern scientific methods have not yet explained why. The failure of science to provide full explanations for all treatments is not unique to homeopathy. Some people feel that if homeopathy appears to be helpful and safe, then scientifically valid explanations or proofs of this alternative system of medicine are not necessary."

In 2008, NCCAM's acting deputy director, Jack Killen, said, in a Newsweek article, "There is, to my knowledge, no condition for which homeopathy has been proven to be an effective treatment." .