It can be frustrating, and sometimes even a little depressing, to be a skeptic. Promoting reason and science-based medicine often feels like a Sisyphean effort that garners lots of hostility and ad hominem attacks from proponents of pseudoscience and few concrete victories. But once in a while, something happens to give a little hope and inspiration.

In 2010, for example, the House of Commons Science and Technology Committee report on homeopathy came out, clearly unmasking homeopathy for the vitalist 18th century relic it is (though, sadly, politics is complicated and often unmoved by mere scientific truth, and the government didn’t eagerly embrace the findings or recommendations of the committee). About the same time, the British Medical Association called homeopathy “witchcraft,” and recommended it no longer be supported by the National Health Service. More recently, the Chief Medical Officer in Britain openly acknowledged homeopathy is “rubbish.” Perhaps there has been a shift in the winds? Maybe there is hope that the institutions of government and organized mainstream medicine here in the U.S. might be willing to start taking a stand against pseudoscience in the way they used to in the days before Wilk vs American Medical Association?

As a veterinarian, I was particularly delighted and inspired in March, 2012 when the Australian Veterinary Association (AVA) joined in this movement and took  a firm and public stand on unscientific therapies, in particular washing its hands of homeopathy:

Australian Veterinary Association (AVA) resources will not be used to promote therapies that, in the Board’s opinion, are not compatible with current understanding of physiology and pathophysiology and have been demonstrated to be ineffective by the current accumulated body of knowledge.

That the Board agreed that the veterinary therapies of homeopathy and homotoxicology are considered ineffective therapies in accordance with the AVA promotion of ineffective therapies Board resolution.

This echoed the policies of the British Veterinary Association, and other national veterinary groups in Sweden, Denmark, and elsewhere in Europe. The idea that the central player in organized veterinary medicine in the U.S., the American Veterinary Medical Association (AVMA), which has as members more than 80% of the licensed veterinarians in the country, could be moved to take a similar stand started to seem like a realistic possibility.

The existing AVMA policy on Complementary and Alternative Veterinary Medicine (CAVM) has some nice sentiments in it.

The AVMA believes that all veterinary medicine, including CAVM, should be held to the same standards. Claims for safety and effectiveness ultimately should be proven by the scientific method… Practices and philosophies that are ineffective or unsafe should be discarded…

However, in the roughly 11 years since that policy was adopted, not a single practice or philosophy actual has been discarded, or identified as inconsistent with the scientific method or established scientific knowledge. It has become merely institutional cover for veterinarians practicing alternative therapies to claim that these are recognized and compatible with scientific medicine despite the lack of meaningful supporting evidence.

So a group of veterinarians from the Connecticut Veterinary Medical Association (CVMA) and the Evidence-Based Veterinary Medicine Association (EBVMA; of which I am currently president), decided to submit a resolution to the AVMA governing body (the House of Delegates), re-affirming that veterinary medicine should be science based and finally identifying homeopathy as the pseudoscientific nonsense it is.

The full text of the resolution can be found here, but the core of it is in these statements:

RESOLVED, that the American Veterinary Medical Association (AVMA) affirms that—

  1. Safety and efficacy of veterinary therapies should be determined by scientific investigation.
  2. When sound and widely accepted scientific evidence demonstrates a given practice as ineffective or that it poses risks greater than its possible benefits, such ineffective or unsafe philosophies and therapies should be discarded.
  3. In keeping with AVMA policy on Complementary and Alternative Veterinary Medicine, AVMA discourages the use of therapies identified as unsafe or ineffective, and encourages the use of the therapies based upon sound, accepted principles of science and veterinary medicine.
  4. Homeopathy has been conclusively demonstrated to be ineffective.

There is nothing here that ought to be remotely controversial for the vast majority of veterinarians who practice conventional medicine. And while proponents of all pseudoscience like to pretend their practices are scientifically legitimate, the evidence that homeopathy is both inconsistent with established science (should not work) and demonstrably ineffective (does not work) is overwhelming. The CVMA and EBVMA accompanied the resolution with a white paper, The Case Against Homeopathy, which illustrated in detail the following points:

  • It is generally accepted in veterinary and human medicine that the safety and efficacy of medical therapies is best determined by scientific investigation and scientific evidence.
  • The principles of homeopathy are incompatible with well-established scientific knowledge.
  • There is abundant pre-clinical research showing most homeopathic remedies (those that are highly diluted) have no biological effects.
  • There is abundant clinical research in humans showing homeopathy to be no more effective than placebo.
  • The limited veterinary research available is consistent with the research done in humans in showing that homeopathy has only placebo effects, not specific therapeutic treatment effects.

The resolution had support among a wide range of veterinarians working in different fields. Official endorsements came from the American College of Veterinary Clinical Pharmacology, the American Academy of Veterinary Pharmacology and Therapeutics, and the American Society of Laboratory Animal Practitioners. A number of individual veterinarians also publically supported the measure.

A particularly compelling letter of support came from Dr. Narda Robinson at Colorado State University. Though supportive of some forms of complementary and alternative treatment, Dr. Robinson was concerned about both the evidence against any real benefit from homeopathy and the official policy of the Academy of Veterinary Homeopathy (AVH) to discourage conventional medical care. The presence of such allies added to the sense that the times were a-changing, and at last we might be able to do something about this ridiculous bit of vitalism.

There was also, however, a conspicuous silence from many organizations whose members aren’t usually practitioners of homeopathy but who, for various reasons, were unwilling to acknowledge publically that it is nonsense. There was hope, for example, that the American College of Veterinary Internal Medicine (ACVIM) would endorse the resolution. One of the most respected specialty colleges in veterinary medicine, this group could have significant influence on the acceptability of pseudoscience like homeopathy.

The ACVIM declined to endorse the resolution despite the fact that most of its members do not accept the scientific legitimacy of homeopathy. The reasoning and individual comments offered in their explanation of this decision exemplifies the flaws in the philosophy of evidence-based medicine that have led the group founding SBM to take on the cause of science-based medicine instead:

It should be stated outright that the BOR believes that evidenced-based medicine should be the foundation of the practice of veterinary medicine as much as possible. Realistically, however, we all recognize that many treatment and diagnostic decisions applied to veterinary patients, both by general practitioners and veterinary specialists are made in the absence of evidence…

If I tried to say that I believe all therapy must be based on scientific evidence and clinical trial data, I would be an absolute hypocrite, and I would be reduced to being able to treat a handful of diseases.

This is the argument that says, in essence, that EBM requires optimal evidence before a judgment can be made, and in the absence of near perfect, gold standard RCT evidence, everyone should be free to do whatever they like based on any theoretical reasoning or personal intuition or experience. This approach, which ignores the vast knowledge we have already accumulated which makes some hypothesis far more likely to be true than others, reduces EBM to an intellectual curiosity with no practical value. If we cannot distinguish between homeopathy and conventional medicine after 200 years of scientific research, then we might as well give up entirely on the notion that science is of any use in informing clinical decision making.

Fifty years ago, we had no clue that genes could be normal, but silenced. We had no mechanism for how non-mutating substances cause cancer. We now know they do. I cannot feel comfortable speaking with strong certainty that an entire form of medicine does not work when it is practiced in many parts of the world, journals describing it are indexed in Pubmed, and many are equally convinced of its efficacy.

This is the familiar fallacy that because unexpected or improbable things have turned out to be true in the past, and because our knowledge is inevitable flawed and incomplete, we must refrain from ever judging anything to be untrue, with dash of the argumentum ad populum fallacy for seasoning.

There are too many shades of grey surrounding what we each do on a day-to-day basis to comfortably single out a particular therapy for condemnation because of a lack of evidence. There are many forms of “unconventional” or “alternative” therapy with no more evidence of efficacy than homeopathy. And even when using “conventional” therapy in an empiric manner, problems with the resolution arise. Every patient empirically treated without a definitive diagnosis is, in essence (in my opinion), a violation of at least the spirit of the resolution (and with as much potential for harm from delayed diagnosis as any non-traditional therapy). Every time I reach for certain dangerous drugs (eg, chemotherapy drugs, glucocorticoids) because I have nothing else to offer, I violate the spirit of the resolution (and arguably in a more severe manner in that my non-evidenced-based therapy has a greater likelihood of causing harm than the homeopathic treatment). Where would/should the lines be drawn then?

Given the necessity in many cases to make decisions with only scant, poor quality or even conflicting evidence an alternative wording to the resolution that many BOR members seemed comfortable with is offered:

  1. Safety and efficacy of veterinary therapies should be determined whenever possible by scientific investigation.
  2. When sound and widely accepted scientific evidence demonstrates a given practice as ineffective, or that it poses risks greater than its benefits, such ineffective and unsafe philosophies and therapies should be discouraged.
  3. Veterinarians may legally employ any therapy not proscribed by applicable laws and regulations governing the practice of veterinary medicine. However, veterinarians have an ethical duty to society, and to their patients and clients, to ignore their biases and instead base their judgments and recommendations as often as possible on the best available scientific evidence.

This statement seems to me to be saying, “We believe science is the best way to validate medical therapies, but we aren’t willing to say that anything is ever invalidated unless nothing we do involves any evidentiary uncertainty.” To suggest that empirical use of chemotherapeutics is roughly equivalent to treating cancer with water is clearly ridiculous. Yet there is a component of humility and a sense of fairness that makes this sort of reasoning very appealing to the majority of veterinarians who don’t believe in homeopathy but are reluctant to criticize their colleagues who do.


While I applaud the recognition of our individual and collective ignorance and limitations, I believe it does no service to our patients and clients if we mistake post-modernism for humility. The evidence against therapeutic bloodletting was no better than that against homeopathy, and it was no less plausible. Should we revive that practice because we have not definitively demonstrated it is useless in all circumstances by extensive and perfect RCTs? Lines should, indeed, be drawn, and while they may not always be perfectly drawn and immutable, they can be based on a thoughtful and reasonable assessment of the available evidence.

As I see it, all conclusions in science are, of course, provisional and subject to revision as new evidence is developed. And our confidence in our conclusions should be proportional to the evidence available to support them. So it is possible evidence could be developed to validate homeopathy as a clinical intervention. Personally, I see this as about as likely as the emergence of evidence that the Earth does not, in fact, revolve around the Sun, but in some theoretical sense at least it is possible. And the evidence concerning homeopathy is not impervious to criticism, especially given the generally low level and poor quality of it. However, if we cannot draw conclusions about a therapy until near perfect evidence is available, then EBM is useless as a decision-making tool.

My own approach is that we must critically evaluate and rank the evidence according to EBM methods, then integrate this with other relevant information, such as biologic plausibility, and make a pragmatic decision based on the evidence that exists. Accepting the provisional nature of such decisions, we must be willing to re-evaluate them as necessary, but it does no good to simply refrain from making them at all if the evidence is less than ideal. We don’t entirely understand the mechanisms of gravity, but we refrain from leaping out of windows all the same.

In the case of homeopathy, the absence of evidence seems very much to be evidence of absence given the implausible foundations and the failure of numerous attempts to validate the method over two centuries. If even this is not sufficient to declare the therapy ineffective (with, of course, the very small caveat that allows for new evidence to someday emerge), then I cannot see how any therapy can ever be discarded or how EBM can provide effective guidance for clinicians in selecting interventions.

Less surprising and disappointing than the failure of support from the reasonable mainstream of veterinary medicine was the opposition from the expected sources. The AVH and the American Holistic Veterinary Medical Association (AHVMA) both opposed it. The AVH attempted to muddy the waters in the usual way by producing a white paper of their own, The Evidence for Homeopathy, which claims to show that homeopathy is based on legitimate, validated scientific principles and has abundant evidence of clinical benefit.

This paper illustrates exactly the points made and demonstrated in The Case Against Homeopathy. Low-quality studies with poor control for bias, confounding, and other sources of error are cited to justify claims that the evidence does not support. Sometimes, even studies which find no effect are cited to support claims of an effect. Bits of legitimate science are misinterpreted to generate the false impression that they validate the implausible theoretical foundations of homeopathy. Clear publication bias in support of homeopathy is ignored whereas negative evidence is dismissed on the basis of presumed individual bias regardless of the methodological controls used to account for this. This document was a transparent attempt to select and distort the evidence in favor of their pre-exiting beliefs.

Though tedious, I thought it might be useful to go through the AVH document point by point, including critically appraising each of the references cited. The result is The Evidence for Homeopathy-A Close Look, which deconstructs the bogus arguments of the AVH in exhaustive detail (for this, I want to specifically give my thanks to the other authors at SBM, to Orac of Respectful Insolence, and to the folks at Rational Veterinary Medicine, where I found invaluable information about some of the research cited in the AVH paper).

Apart from the AVH attempt to manufacture scientific legitimacy for their approach, there was the usual hue and cry of a less academic nature. The folks at offered some of the usual hysteria and hyperbole about “health freedom” and the right to peddle and procure whatever medical interventions anyone wants, regardless of evidence concerning safety or efficacy. And one leading opponent of the resolution, a homeopath involved in the AVH and often seen lecturing on homeopathy at mainstream veterinary continuing education meetings, went so far as to compare this resolution to the Holocaust: “She felt that this was her personal Kristallnacht, that the walls came down around her and that she was being marginalized from within her own AVMA.” The AVH submitted a letter full of smoke and mirrors and outright error commenting on specific statements in The Case Against Homeopathy, which I have responded to point by point. And apparently, individual veterinarians worried about losing their freedom to employ imaginary therapies contacted the AVMA to protest the shocking and outrageous idea of admitting homeopathy doesn’t work. About 700 emails and 250 phone calls were apparently received by the AVMA condemning the resolution. It goes almost without saying that the AVMA did not hear from nearly as many skeptics willing to openly speak against homeopathy.

So with pseudoscience and outrage pitted against a mountain of scientific evidence, any guesses as to the outcome?

Well, technically it wasn’t a defeat. The House of Delegates voted by about 3:1 not to vote on the content of the resolution but to refer it for evaluation to the committee that wrote the current CAVM policy quoted above. The same policy which made reasonable noises about the importance of science 11 years ago and has been rather quiet since in the face of apparently growing infiltration of homeopathy and other pseudoscientific practices into the mainstream. I’m not directly involved in the politics or the process, but my guess is the resolution will die quietly in committee, or perhaps be replaced by more vague noises about science and research without any clear statements about the validity of any specific intervention.

So are we slipping into a medical Age of Endarkenment in the U.S.? We still pay lip service to science evidence and reason, but even the best educated and trained among us accept shoddy science and postmodernist rationalizations as reasons to refrain from declaring even such egregious nonsense as homeopathy as out of bounds. It’s true, there are only about 130 members in the AVH, so homeopaths are a tiny minority within the veterinary profession. But with the complicity of the majority, unwilling to criticize anything our colleagues do, this minority can continue to sell pseudoscience and placebos to their clients.

And the AHVMA, which represents CAVM in general, is much larger and more influential than the AVH. They have recently raised about $400,000 to promote “integrative medicine” at mainstream veterinary schools, with an ultimate goal of $20 million and multiple academic centers promoting alternative therapies, positioning themselves as the Bravewell Collaboration of veterinary medicine. And despite their claims to respect science and support rigorous research, they have thrown their lot in decisively with the magic water that is homeopathy. What can skeptics use to combat those resources, other than mere facts and evidence, which seem less persuasive to our otherwise mainstream colleagues than we might hope?

The passionate few who are believers cannot, of course, make homeopathy anything other than a marginal practice, in most cases just added on to real medicine in true “integrative” fashion. After all, it doesn’t actually work. But the hope that we might actually see the death of it alltogether seems distant indeed. Like the proponents of intelligent design, homeopaths seem to be having some success generating a maufacturoversy, suggesting there is some legitimate scientific dispute concerning the plausibility and efficacy of homeopathy. And few of my colleagues in veterinary medicine seem inclined to look at the evidence critically and in depth themselves to see that there is, in fact, no real doubt or legitimate dispute. Money, popularity, and the voice of the passionate minority of believers seem unlikely to yield to mere reason and evidence, especially when shielded by the apathy or post-modern neutrality of the majority. Perhaps “Age of Endarkenment” is going a bit far, but some days the victories of the Age of Enlightenment seem evanescent, and it is clear we shall have to keep rolling the same old boulders up that hill for the forseeable future.



Posted by Brennen McKenzie

Dr. McKenzie has always pursued a wide range of interests both within and outside of veterinary medicine. After completing a bachelor’s degree with majors in English Literature and Biology at the University of California at Santa Cruz, he followed the dream of becoming a primatologist. He obtained a Master’s in Physiology and Animal Behavior and worked for several years in environmental and behavioral enrichment for captive primates. Switching gears, Dr. McKenzie then attended the School of Veterinary Medicine at the University of Pennsylvania and began working as a small animal general practice veterinarian. In the course of trying to improve his knowledge and better educate his clients, he discovered evidence-based veterinary medicine, and he has served as President of the Evidence-Based Veterinary Medicine Association. This has led to numerous opportunities for speaking to veterinarians and the general public about evidence-based veterinary medicine and some of its ideological competitors. Dr. McKenzie has also reached out to the public through SkeptVet Blog, his contributions to the Science-Based Medicine Blog, and media interviews on veterinary medical topics. While working as a practitioner, speaking, and writing, Dr. McKenzie has continued to pursue post-graduate training and completed his MSc in Epidemiology at the London School of Hygiene and Tropical Medicine in 2015. In his sparse free time, Dr. McKenzie enjoys reading, hiking, playing his mandolin, travelling with his family, and sitting on the couch with his dogs watching the hummingbirds and woodpeckers outside his living room window.