To begin with, the blog post must be acknowledged as being a mere snapshot of a very vast field. I apologize for the incompleteness, but an tire book would be required for a full understanding, and I do suspect that it would be quickly out of date.
As some background, Homeopathy has a long history of clinical trials, and testing in humans. These trials have always generated a great deal of contention, and it has always been disputed that the effect of Homeopathic interventions is due to the effect of the remedies. Other factors, such as the counseling, other lifestyle interventions recommended, and even the poor social skills of allopathic doctors in comparison have been suggested as the factors responsible. The most popular explanation has been the placebo effect, in short, the phenomena of patients healing despite a treatment which is not expected to effect them. Homeopaths have responded to these criticisms with record of the treatment of children and animals, presumably not subject to placebo effect, and experiments on model organisms, plants, cell cultures in test tubes or other biological systems, which most definitely are not placebo susceptible.
Homeopathy has a very long history of evaluation in model organisms. While the primary data of Homeopathy have always been gathered in provings of substances on healthy individuals, many researchers have experimented with homeopathically prepared substances, and their effects on living organisms. The most interesting example of this work in the 19th century is that of Charles Darwin, (Many thanks to Dana Ullman for his excellent work on this subject, which is my primary source). Charles, having yet to write his famous book on evolution, was extremely ill, having failed to gain relief from convention treatment, sought care from Dr James Gully, a medically trained homeopath, whom also used hydrotherapy a great deal (in a therapeutic style that is suspiciously similar to modern Naturopathic medicine).
Darwin was not a great believer in Homeopathy, and was confounded by this recover for the rest of his life. He conducted one of the earlier series of experiments using model organisms, in his case the Drosera plant ( itself also a homeopathic remedy). In his experiments, Darwin was able to show a response by the Drosera plants to 1/20 millions of a grain of an ammonia salt. Darwin was enormously reticent to publish this information, fearing it would detract from the reception of his already contentious evolutionary theory.
Since this rather historically fascinating example, a large number of studies have been conducted. As a May 2018 review of the literature concluded, there were about 183 publications on the subject. Publications averaged about 2 per year from the 1970s-200s with a jump to about 5.5 per year afterwards. Furthermore quality of publications has markedly increased with 13% of publications high quality before 2000 compared to 44% afterwards.
One specific aspect of this research, is Homeopathic research on plant models. One review in 2015 found 157 studies, but that only 48 included adequate information to evaluate them. A second study done in 2018 found similar results. Several studies were replications, on successful, but 4 unsuccessful, with several possible variables identified.In general standardized procedures were recommended, including negative controls, and better control and identification of interference factors.
Research on abiotically stressed plants ( plants stressed by environmental conditions, instead of pathology) have also been accomplished, with reproducible and significant effects found, including effects beyond Avogadro’s number, although interestingly, one replication occurred generating opposite results. Again the authors stressed the need for replication and standardized procedures. A similar study on diseased plants as well was done in 2009. The authors as well found significant and reproducible effects of Homeopathic preparations on plant models, again beyond Avogadro’s number, though again standardized procedures are required, as is more replication.
Another fascinating body of work is the examination oh Homeopathic remedies through the medium of NMR. This method has, interestingly, been shown by several studies, to be able to detect differences between different Homeopathic potencies. In one recent study, changes in the emission from water was determined to be altered by both crude and ultramolecular homeopathic preparations in water. In another fascinating study, differing triturations of the same remedy at a different potency also displayed differing emission spectra. Another study examined triturated potencies of zincum metallicum in terms of their physical properties. Many properties were not altered, but did find that thermogravimetric and differential scanning calorimetry differed between homeopathically prepared and control samples.
The final say in this matter should perhaps be towards the greatest study on the subject, a 2015 literature review solely on replications in in vitro research in Homeopathy. This paper focused solely on experiments involving potencies diluted beyond Avogadro’s number, with no possible confounding by particles being present.Trials were classified as yielding either compatible results, no results, or opposite results. The null hypothesis of this trial was that no results was the default states, indicating no physiological effect. Of 126 studies found 98% were found to be replications, with 70.4% achieving comparable results, 20.4% obtaining opposite results, and 9.2% no results. With these results, the null hypothesis can be firmly rejected. In terms of raw numbers 28 experimental models were replicated, 24 with comparable results, 12 with no effect, and 6 with opposite effect. Five models were externally and independently replicated with comparable results.
Within this paper we can clearly see definite progress in the in vitro science of Homeopathy. A previous publication in 2007 found similar ( though lower numbers) of results, with a notation that both high quality trials do show effects and that no model was universally reproducible yet.
The issue of methodology looms large in this field of research. To understand this we will follow the ongoing and fascinating saga of one research model’s development, the Basophil model.
The Basophil model of research in Homeopathy began by accident, when a laboratory assistant of Jacque Benviniste, used a wrong (diluted) preparation of Immunoglobulin E, which caused a reaction ( degranulation) in the basophils it was administered to. Beneviniste noticed this phenomena, and began experimenting with it. He discovered that agitated dilutions performed better than simple dilutions, and this drew a strong parallel with Homeopathy, which was much more salient in French medicine than in North America. Beneviniste shared his research with 4 labs throughout the world, which managed to replicate the results.
Beneviniste published his paper in Nature, and it was accompanied by an unprecedented editorial, urging a suspension of judgement over the results, and distancing the editorial team from the research. Subsequently, the magician James Randi (who is not, despite his pretensions, a scientist), and John Maddox and fraud expert Walter Stuart. They, lacking expertise in the technique, in a very small number of attempts, failed to replicate the experiment, and concluded it was a fluke caused by sloppy methods or some other error, ignoring replication having already been done by several skilled teams throughout the world.
Several other teams attempted to replicate the findings, with mixed results. According to a lacture by Dr Peter Fischer, the experiments were replicated about 30% of the time. This was largely to do with the methodology. In Beneviniste’s methods, homeopathic style preparations of Immunoglobulin E were prepared and administered to cultures of basophils. When basophils come into contact with Immunoglobulin E, degranulation is the result. At differing dilutions of Immunoglobulin E, differing rates of degranulation were observed in some cultures, including those beyond avogadro’s number. Numerous factors appeared to be involved in whether basophils degranulated, resulting in the lower 30% reproduction rate.
Not that none of this subtlety in research methodology has ever been reported in the conventional media. Nor has the many replications been mentioned. Beneviniste is still cited as a fraud by many on the basis of a single experiment by non scientists, despite repeated ( though low) replication by other skilled scientists. As I have repeatedly shown (here and here) many organizations opposed to Naturopathic medicine and Homeopathy will use a number of fake news tactics to discredit therapies, despite often very good science in support of them.
Benevinistes model was later modified. As in actual clinical practice, where only people in certain pathological states were found to respond to a remedy, it was found that basophils responded to Homeopathic preparations when in a certain pathological state. Basophils here hence sensitized to pathological stimuli, then exposed to homeopathic dilutions of histamine, and then exposed to an antigen. The percentage of basophils that degranulated was measured, and found to be lesser in the group treated with Homeopathic histamine. This response did vary with the homeopathic potency of histamine administered, with a bell curve style peak from 15-17C. The main paper with this updated model was published in the journal Homeopathy in 2009.
The advantage of this more complex procedure using presensitization was a procedure which was much more consistent in terms of replication. This model has been replicated repeatedly, one such published replication can be found here. The procedure was, in 2009, replicated by 4 independent laboratories. This number has likely increased considerably in the 9 years since. According to a lecture by Dr. Fisher, this model was about 60% replicable, having far fewer variables influencing results.
The latest methods in this field are achieving consistent and reproducible effects using sensitized organisms, a phenomena that parallels clinical observation in Homeopathy. Interestingly this body of research has confirmed one clinical observation of Homeopathy seen for decades, that of a bell curve. Organisms tend to respond to only a certain range of potentiates, and both higher and lower potencies than their range will produce no results.
This is in strong contrast to the conventional model of pharmacology, which has found S shaped curves far more typically when observing physiological responses to drugs. Drugs, when administered to a responsive system, typically have a threshold below which they have no activity, followed by a phase in 
which small increases or decreases in concentrations of a drug cause massive changes in activity, followed by a plateau in which the effects of a drug do not increase very much, compared with the rapid phase. These two curves are displayed in the figure to the right. S curves are shown in blue, and bell curves in red.
This contrast has fascinating ramifications. The first being that Homeopathic medicines do not act like crude drugs, that there is a fundamental activity, profoundly based on the amount of potentisation and triturations, that exerts a physiological effect on the body, independent of chemical constituents. This implies a number of factors playing into biology that have very little understanding within modern biology. A number of profound biological and medical discoveries await for those brave enough to explore the implications of these data.
In the face of this large amount of research, arguments that Homeopathy has no effect are not sustainable. Those who make such arguments are either ignorant, or are deliberately being deceptive.
To summarize, an available research presentation on the latest Homeopathy research is given below.
Thank you for reading!
Image Credit: https://commons.wikimedia.org/wiki/File:Funci%C3%B3n_sigmoide_02.svg
