In 2012, we published a systematic review of adverse effects of homeopathy. Here is its abstract:

Aim: The aim of this systematic review was to critically evaluate the evidence regarding the adverse effects (AEs) of homeopathy.

Method: Five electronic databases were searched to identify all relevant case reports and case series.

Results: In total, 38 primary reports met our inclusion criteria. Of those, 30 pertained to direct AEs of homeopathic remedies; and eight were related to AEs caused by the substitution of conventional medicine with homeopathy. The total number of patients who experienced AEs of homeopathy amounted to 1159. Overall, AEs ranged from mild-to-severe and included four fatalities. The most common AEs were allergic reactions and intoxications. Rhus toxidendron was the most frequently implicated homeopathic remedy.

Conclusion: Homeopathy has the potential to harm patients and consumers in both direct and indirect ways. Clinicians should be aware of its risks and advise their patients accordingly.

The paper prompted a number of angry reactions from proponents of homeopathy who claimed, for instance, that homeopathic remedies are highly diluted and thus safe. We responded that homeopaths can nevertheless be dangerous to patients through neglect and bad advice by homeopaths, and that not all homeopathic remedies are highly diluted, and that some might be toxic because of poor quality control of the manufacturing process.

Now, a different group of researchers have looked at the problem from a slightly different angle and with different methodologies. This systematic review and meta-analysis by researchers from NAFKAM focused on observational studies, as a substantial amount of the research base for homeopathy are observational.

Eight electronic databases, central webpages and journals were searched for eligible studies, and a total of 1,169 studies were identified, 41 were included in this review. Eighteen studies were included in a meta-analysis that made an overall comparison between homeopathy and control (conventional medicine and herbs).

Eighty-seven percent (n = 35) of the studies reported adverse effects. They were graded as CTCAE 1, 2 or 3 and equally distributed between the intervention and control groups. Homeopathic aggravations (homeopaths believe that, when the optimal remedy is given, patients will experience an aggravation of their presenting symptoms) were reported in 22,5% (n = 9) of the studies and graded as CTCAE 1 or 2. The frequency of adverse effects for control versus homeopathy was statistically significant (P < 0.0001). Analysis of sub-groups indicated that, compared to homeopathy, the number of adverse effects was significantly higher for conventional medicine (P = 0.0001), as well as other complementary therapies (P = 0.05).

The authors concluded that adverse effects of homeopathic remedies are consistently reported in observational studies, while homeopathic aggravations are less documented. This meta-analysis revealed that the proportion of patients experiencing adverse effects was significantly higher when receiving conventional medicine and herbs, compared to patients receiving homeopathy. Nonetheless, the development and implementation of a standardized reporting system of adverse effects in homeopathic studies is warranted in order to facilitate future risk assessments.

While these results are interesting, they have to be taken with a pinch of salt and beg a number of questions:

  • Is there proof that aggravations exist at all?
  • How can one differentiate them from adverse effects?
  • As even placebos are known to cause adverse effects (nocebo effects), how can one be sure that the adverse effects of homeopathy are not nocebo effects?
  • Is it a good reason to focus on largely inconclusive observational studies, because a substantial amount of the research base for homeopathy are observational?
  • Can one produce conclusive results by meta-analysing inconclusive studies?

For me, the most impressive findings of this review is that in total 86 studies had to be excluded by the authors because they reported no adverse effects or aggravations. I think this renders the interpretation of the evidence from the 41 studies they did include even more flimsy. In fact, I don’t see how any meaningful conclusion can be drawn at all – except of course that many researchers of homeopathy violate the rules of research ethics by not reporting adverse effects in their studies.

As to aggravations, we clearly need to rely on placebo controlled studies, if we want to find out whether they exist at all. This we have done in our 2003 paper:

Homeopathic aggravations have often been described anecdotally. However, few attempts have been made to scientifically verify their existence. This systematic review aimed at comparing the frequency of homeopathic aggravations in the placebo and verum groups of double-blind, randomised clinical trials. Eight independent literature searches were carried out to identify all such trials mentioning either adverse effects or aggravations. All studies thus found were validated and data were extracted by both authors. Twenty-four trials could be included. The average number of aggravations was low. In total, 50 aggravations were attributed to patients treated with placebo and 63 to patients treated with homoeopathically diluted remedies. We conclude that this systematic review does not provide clear evidence that the phenomenon of homeopathic aggravations exists.

What is interesting, from my perspective, is the fact that the NAFKAM authors chose to ignore our 2012 paper completely (even though it is highly relevant to their paper and was not published in an obscure journal) and elected to completely misinterpret the findings of our 2003 paper (stating this about it: Grabia and Ernst reported a total of 103 cases of homeopathic aggravations in 3437 participants (3%), while, in fact, our paper demonstrated that aggravations are a homeopathic figment of imagination).

I wonder why.

In the past, NAFKAM did not have the reputation of doing research that was overtly biased towards homeopathy. Recently, the head of the team retired and was replaced by Miek C. Jong who is a co-author of the present review (plus head of CAMcancer, an organisation of which I am a founding member and which did, I think, some good work in the past). She happens to have a long history as a homeopath or homeopathic researcher and is co-author of many papers in this area. Here are three of her conclusions:

Could it be that, within NAFKAM, the attitude towards homeopathy has changed?

18 Responses to Adverse effects of homeopathy and aggravations at NAFKAM

  • Edzard, every time you write about homeopathy you reveal how little you know about it. I would think in your field you would want to know something about homeopathy if you are going to write about it.

    “Is there proof that aggravations exist at all?”
    “How can one differentiate them from adverse effects?”

    An aggravation precedes a cure or at least a significant improvement in their health. If there was no amelioration or cure then there was no aggravation. If there was a worsening of symptoms following the remedy then it was the wrong remedy, it had no effect and the disease has progressed. Well documented in homeopathic literature, but I guess you havent read any of it so wouldnt know.

    • so, a sypmtom [say headache] that is noted before a cure is an aggravation. if there was no cure and the symptom disappeared due to the natural history of the condition, it is an adverse effect. how do you tell the difference?
      I think your comment shows that you have not understood a lot of things.

      • An aggravation is actually a misnomer. An aggravation is really a proving of the remedy; it is causing or aggravating the symptoms that it will cure because the remedy was given in too strong a potency.
        An existing symptom that worsens after taking the remedy and before the cure, indicates an aggravation.
        A new symptom that develops after taking the remedy and before the cure, possibly indicates an aggravation.
        If the new symptom is known from the materia medica of the remedy, it is likely an aggravation.

        If a single symptom disappeared spontaneously without curing the balance of symptoms, how is that an adverse effect? As you say, its probably just the natural history of the condition or it could be palliation because the remedy was not similar enough to cure. How does that reflect negatively on the remedy at all? A homeopath would look for another remedy lacking significant improvement due to the previous one.

        • “If the new symptom is known from the materia medica of the remedy, it is likely an aggravation.”
          as there no symptom exists that is not in the MM, all side-effects can be aggravations [as long as they occur BEFORE the perceived ‘cure’]
          WHAT BS!!!

          • Roger’s contributions to this blog do give a fascinating insight into the warped mindset of homeopaths and the levels of self-deception they have to employ to convince themselves that their sugar pills and shaken water are actually doing something.

          • Where do you get the idea “there no symptom exists that is not in the MM”?
            Have you read any MM? Every remedy has a very unique characteristic set of symptoms.
            Every remedy doesnt have every symptom!!
            Again, I have to wonder how much you know about homeopathy.

            In homeopathy a symptom in the MM is characterized as thoroughly as possible. A well specified symptom is characterized by as many as possible of the following: side of the body, time of occurrence, modalities (what makes it better or worse), extensions, location of the sensation annd quality of the sensation. If somebody develops “a headache” after taking a remedy you wouldnt just assume it was an aggravation unless the specific symptoms of it matched the characteristics of headaches that the remedy is known to cause.

            That being said, MM is never complete especially for little known remedies so its possible that it is still an aggravation because that particular type of headache was previously unknown for that remedy.

          • Either you understand homeopathy and therefore don’t use it
            You use it and therefore don’t understand it.


    • Next up – the “healing crisis”?

      From Hanhemann onwards, there is a long literature of finding excuses for the lack of efficacy of homeopathy.

    • Roger: Please stop this nonsense.
      You don’t need to get presents left at the foot of your bed to know perfectly well there is no ‘Santa Claus’.
      Or to find a coin under your pillow to know there is no tooth fairy.

      If you believe ‘aggregations’ have any material effect in the immanent world, I’m afraid you’re going to have to give better evidence that recite your, or your patients’, beliefs.
      Good luck with that – and try to move on. Please.

      • Richard, why dont you learn something about the subject of homeopathy first hand instead of regurgitating ignorance absorbed from others.

        Are you aware that the mechanistic paradigm cant explain life or consciousness?

        • So many [citations required].

          • @ Roger

            the only thing one needs to know about homoeopathy is that it is complete and utter batshit crazy nonsense.
            What is hilarious is seeing its proponents twisting themselves into pretzels trying to justify its ridiculous contradictions and inherent impossibilities.

            Hahnemann must have been high on something when he dreamed up this magik alchemy – or perhaps it was a practical joke but people took him seriously? It is counter-intuitive, illogical and anti-science – and repeatedly fails when tested empirically.
            Notions such as the hilariously mis-named “provings” are so ludicrously antithetical to their stated purpose and to common sense and any scientific purpose as to make them more like some form of children’s game or a pasttime for drunken misfits.

            And what to make of “succussing?” The notion that somehow thumping liquid on a leather surface a magical number of times will miraculously endow it with a supernatural quality? Surely this belongs more in a religious realm rather than in any pretence of science? I am only surprised that some incantation is missing.

            And of course there is no doubt that the desperate need of homeopaths to believe in their creed with religious zeal in spite of the lack of evidence and in the face of all the evidence to the contrary gives even more credence to the notion that it has much more in common with a religion than a scientific endeavour?

            Before moving on to metaphysics I suggest you ask yourself why homeopathy can’t explain itself?

          • Hahnemann must have been high on something when he dreamed up this magik alchemy – or perhaps it was a practical joke but people took him seriously? It is counter-intuitive, illogical and anti-science – and repeatedly fails when tested empirically.

            No, Hahnemman was onto something. At the time, the standard of care was purging and bloodletting, which was actively harmful, sending as many to their graves as the diseases themselves. Hahnemman’s treatment proved effective at distracting the quack long enough for nature to heal the patient.

            In other words, bed-rest and hydration works better than half-murdering your patient just to make yourself feel useful. Normally I’d ask “Who knew?”; but since the Galenites demonstrably didn’t, and were far too up themselves even to ask themselves “But what if we’re wrong?”, that doesn’t really work as a rhetorical flourish.

            Hahnemman’s error was in blindly assuming the improved health of his patients was the product of his ritualistic religious practices, as opposed to the real reason: keeping them the hell away from those murderous Galenite loons. It worked, and it flattered Hahnemman’s ego and wallet, and that was good enough for him.

            It wasn’t until Redi, Semmelweis, Snow, and Pasteur finally put the nails in Galen’s coffin, that Hahnemman’s “treatment” was proved to be no more than fanciful placebo, and real medicine that actually works—and can prove that it works—began to be developed.


            So I’m not going to be as hard on Hahnemman himself as his own mistake was an all-too-human one, and he was born in an age when nobody knew how disease worked and everyone was still fumbling in the dark; and being completely wrong about everything was ubiquitous and normal. Nobody back then had your benefit of two hundred years’ hindsight, so you should not judge them on that.

            But to his children—the excetable Ullmans, Hümmers, Dendras, RGs, and Rogers, who have no such excuse to hide behind now—you’re delusional disgraces, pathological liars to yourselves as well as others, and evangelically active dangers to life and limb, absolutely no better than those ghastly Galenites that Hahnemman himself once battled.

          • @ john travis
            You are using the same “infallible” logic about the homeopathic proving that doctors used when Semmelwies suggested that it might be a good idea for doctors to wash their hands. “I dont need to wash my hands. I _know_ they wont infect the next patient because my phlogistic paradigm tells me so.”

            “A homeopathic proving wont cause any effect; I _know_ because my mechanistic paradigm tells me so.” Please dont bother to challenge your flawed limited understanding of the universe with direct experience.

            Let me know when you have developed a thorough explanation for consciousness based on the mechanistic paradigm.

          • I know provings don’t work for me because I have done several.

          • If doctors “know how disease works” why cant they cure more than a few Chronic diseases?

            Probably because they dont know how health works, either.

  • Prof Ernst: “I know provings don’t work for me because I have done several.”

    More importantly, what does proving that you can perform a proving actually prove? I mean, I can follow the recipe for tattie scones but that doesn’t make me believe in the King of the Potato People.

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