A recent peer reviewed article authored by Professor Peter Lees, Emeritus Professor in Pharmacology at the Royal Veterinary College (RVC), definitively explains why homeopathy in veterinary care can appear to be effective because of perceptual mistakes, when in fact these products are fundamentally non-effective.
This ground-breaking study also has significant implications for the use of homeopathic treatments in people.
The article, ‘Comparison of veterinary drugs and veterinary homeopathy’ (part 1 and 2) has been published by Veterinary Record, will be of particular interest to vets, doctors and scientists, as well as anyone who has used homeopathic products for themselves or their animals.
The article shows how many phenomena perceived in laboratories and clinical environments are not the result of understood causes, but rather simple coincidence. This can mean, for example, that health improvements can be erroneously linked to an ineffective product – such as a homeopathic ‘remedy’.
The article shows that there are many psychological biases that can mislead physicians in judging the effectiveness of treatments. Because of the inherent uncertainties in assessing the body’s response to treatments, cognitive bias can prevent a vet or medical doctor from recognising that it was not their intervention that caused a patient to get better.
This misperception of what happened, what caused something to happen, and the body’s own capacity to heal, has created the space in which ineffective treatments become regarded as having efficacy. This has happened in both human and veterinary medicine, with debates about the efficacy of homeopathy raging for decades.
Homeopathy is most frequently used to treat chronic conditions with fluctuating signs, or acute, self-limiting conditions. These are precisely those conditions for which assessment of treatment responses is most difficult and prone to error because of the natural history of the disease and subjective biases.
Clinical trials are also the subject of numerous biases, in particular confirmation bias, ascertainment bias, selection bias and publication bias which all apply with randomised clinical trials (RCTs). The ideals of bias-free standards are not always achieved in human RCTs of conventional medicines. This study shows that they are very rarely achieved with veterinary RCTs of homeopathic treatments.
By better understanding processes that can lead to misperceptions about clinical and healing phenomena, veterinary and medical practitioners can have a clearer idea about which clinical interventions are more effective and which agents can be discounted as coincidental to healing. The article is aims to provide a first step in that process for the veterinary and medical community.
The Royal College of Veterinary Surgeons Standards Committee and Council are currently formally reviewing their position and guidance regarding complementary and alternative medicines, including homeopathy, making this article’s findings even more timely. Both papers highlight ethical concerns regarding veterinary surgeons treating animals with an ineffective, implausible and irrational therapy.
Use of Homeopathy in veterinary care
For many years after its invention, around 1796, homeopathy was widely used in humans and later in other animals. Over the intervening period, pharmacology emerged as a science and the mainstay of veterinary and medical therapy. However, there remains a small but significant use of homeopathy by vets.
Homeopathic products are sometimes administered when conventional drug-based therapies have not succeeded. However, they are also sometimes used as alternatives to licensed pharmaceutical products with proven mechanisms of action. Therefore, animals with conditions that could be treated by an approved veterinary medicine are going without effective treatments in favour of ineffective homeopathic products. Furthermore, not all homeopathic products are neutral in their effect and are sometimes administered in highly concentrated forms that can potentially harm patients.
Although homeopaths report that their remedies are effective when used in their practice, efficacy beyond placebo is not apparent in well-controlled clinical trials that eliminate biases and other non-specific effects.
Factors that should be considered when assessing the efficacy of any product include: specific effects of the treatment, placebo effect, bias in observers’ assessment of patients’ response to treatment, the natural course of the disease, and the effects of concurrent management of the illness. Without this process, after the use of drug-products and homeopathic ‘remedies’ alike, there is a risk that ultimate significance is wrongly given to the product administered.
The article acknowledges that there may be value in the counselling or psychotherapeutic aspects of human homeopathic consultations. However, they emphasise that the placebo effects generated by homeopathic products in patients who believe in such treatments would be lacking in veterinary medicine, as animals are not able to ‘believe’ in certain treatments.

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