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Homeopathy and adverse effects

Clinical bottom line:

Homeopathy remedies in high dilutions appear to be relatively safe. The mean incidence of adverse effects was higher with homeopathy than with placebo, but all were mild and transient. However, adverse event data is poorly and inconsistently, collected and reported so this conclusion should be interpreted with caution.

It is common belief that homeopathic remedies are safe due to the high dilution of the original substance. Adverse events of drugs in general are poorly reported in the medical literature.

Systematic review

Dantas F; Rampes H. Do homeopathic medicines provoke adverse effects? A systematic review. 2000. British Homeopathic Journal; 89 (1): S35-38

Date review completed: 1995

Number of trials included: 19 clinical trial reports, 19 case (or case series reports) and 15 homeopathic pathogenetic trials

Control group: active and placebo

Main outcomes: Treatment related adverse effects

Inclusion criteria were any published reports of adverse events following homeopathic treatment, any study architecture (case reports, trials etc.), published in English language. Experimental trials of homeopathy on healthy volunteers were also sought.

Reviewers conducted heroic searches including the main databases, specialist journals, manufacturers of homeopathic remedies, and drug regulatory agencies in the USA and UK, and experts in the field were contacted. Published reports were assessed for quality and a judgement made by the reviewers on the causation of the AE reported.


Clinical trials

The mean number of patients reporting at least one adverse effect with homeopathy was 9.40 and with placebo 6.17 in a total of 12 trials. The relative risk was 1.52 (no confidence intervals reported and no data presented to allow calculation of this). The adverse effects were mild and transient in nature. Perhaps more striking is the fact that 36 reports did not report on collection or incidence of adverse effects at all.

Case reports

Very few case reports described adverse effects. Those that were reported tended to be symptoms described as aggravation of the pre-existing symptoms.