The dilutions and the memory of water theory
The aspect of homeopathy that is implausible for many people is that the medicines are often ? though by no means always ? diluted to the point where there may be no molecules of original substance left. One of the leading current proposals for how such 'ultramolecular' dilutions work is that water is capable of storing information relating to substances with which it has previously been in contact.
The structure of water
Recent research on hydrogen bonds in water provides some support for this 'memory' theory. The Swiss chemist, Louis Rey, found that the structure of hydrogen bonds in homeopathic dilutions of salt solutions is very different from that in pure water.2 He reached the conclusion that the phenomenon results from the vigorous shaking of solutions that takes place during homeopathic 'succussion'. Moreover, using the laboratory technique called spectroscopy, other researchers have found that different homeopathic medicines and different dilutions of the same medicine can be distinguished from each other, even though all should contain nothing but water.
An alternative mechanism is suggested by the results of research from South Korea. Studies on molecular clustering in water solutions showed that as a solution is made more and more dilute, very stable and larger ?clumps? of material develop in dilute solutions rather than in more concentrated solutions.4 This means that residual molecular clusters of the original substance might just be present in homeopathic dilutions. Succussion might also be responsible for creating very tiny bubbles (nanobubbles) that could contain gaseous inclusions of oxygen, nitrogen, carbon dioxide and possibly the homeopathic source material.
Highly diluted substances exert an effect
However they work, there is increasing evidence that homeopathic dilutions have a demonstrable effect on living organisms examined under laboratory conditions. Researchers in Germany have observed an inhibitory effect of an ultra-diluted chemical on the bacterium Vibrio fischeri.5 And there is important work from a consortium of European laboratories showing that very high dilutions of histamine may exert a biologically significant effect on the white blood cells that take part in the immune response.
Positive outcomes in 75% of studies
Viewing the evidence overall, there is some experimental support for the idea that ultra-molecular homeopathic dilutions may possess unique physical properties and can exert physiological effects. A systematic review evaluated 67 in-vitro experiments in 75 publications of research on homeopathic dilutions.7 A majority of papers reported measurable effects from highly diluted substances. Positive findings were obtained in nearly three-quarters of all replicated studies, but no positive result was stable enough to be reproduced by all investigators.