The available evidence suggests that hazards from homeopathic products are modest in comparison with those of conventional medicine.¹ According to conventional toxicology, any toxic substances in a homeopathic medicinal product will be diluted well below hazardous levels. A theoretical hazard could be the failure to dilute sufficiently, but there is no record of this happening in any manufactured product. Manufacturers of homeopathic medicinal products are well aware of the potential for manufacturing errors and adhere to international guidelines for Good Manufacturing Practice (GMP) just as assiduously as other pharmaceutical manufacturers.

Although homeopathic medicines are typically too dilute to cause toxic effects, adverse effects have been reported in four experimental studies in animals.² A published systematic review of the safety of homeopathy included a search of the English language literature between 1970 and 1995, enquiries with regulatory agencies in the UK and the USA, and homeopathic pharmaceutical companies.³ The conclusions were: homeopathic medicines may provoke adverse effects, but these are generally mild and transient; adverse effects of homeopathy are under-reported; there are cases of ‘mistaken identity’ where herbal medicines have been described as homeopathic. In two studies, adverse reactions were observed in approximately 2.7% of the patients ^{4, 5}; in a third study, 7.8% of homeopathy patients (mainly paediatric cases with specific acute pathology) had adverse reactions, compared to 22.3% in the corresponding group receiving conventional treatment.⁶

These reports do not usually include those defined as ‘homeopathic aggravation’ in the true sense of the word, unless they were of such an intensity as to warrant reporting and require medical intervention (generally by antidoting the medicine). This is because the homeopathic aggravation is a temporary worsening of existing symptoms following the administration of a correctly chosen homeopathic prescription, which indicates that a favourable response to treatment is followed by an amelioration of the patient and disturbance being treated. While the existence of homeopathic aggravations is not disputed in homeopathy, little research has so far addressed this phenomenon. Endrizzi et al. observed these aggravations in 26.3% of their patients. However, a systematic review of placebo controlled RCTs failed to demonstrate that aggravations happen more frequently in the verum groups compared to the placebo groups.⁷ They concluded that: either the aggravation does not exist or the methods used to examine it are inadequate. Furthermore, it is not usual practice to document this effect and distinguish it from adverse effects. Interestingly the authors did find that collectively about three times more adverse effects were reported in the verum groups compared to the placebo groups.  Bearing in mind that all studies were double-blind, this fact implies firstly that homeopathic remedies are not totally devoid of adverse effects and secondly that homeopathic remedies are not clinically identical to placebos.

The main risks associated with homeopathy are probably indirect, relating to the prescriber rather than the medicine.⁸ These indirect risks may occur when homeopathic doctors/practitioners are not fully trained; when they do not follow the professional code of ethics; when they disregard possible interactions with conventional prescription drugs and contra-indications; when they do not make a comparative assessment as to the therapeutic possibilities of homeopathy versus any other interventions necessary, including biomedicine, or when the treatment is not adjusted or modified according to the condition or constitution of the patient.

It may be concluded that if homeopathic medicinal products completely satisfy quality control and GMP requirements, they can be regarded as generally safe.

Dr Ton Nicolai
President of European Committee for Homeopathy