The most controversial aspect for critics is that the remedies are made using extremely high dilutions of homeopathic substances. Conventional science indicates that most homeopathic remedies are so dilute that none of the original substance can possibly be present. However, remedies are made by a process of dilution and vigorous shaking (known as succession) and this combination seems to change the properties of the diluted liquid.
Research over the last few years has led scientists to acknowledge that the structure of water is not as simple as once believed and that vigorously shaken, ultra high dilutions have physical and chemical properties very different from pure water. Researchers like Rustum Roy and Iris Bell have carried out important research in this area.
This site gives a good overview of one aspect of this debate
http://www.livescience.com/environment/041201_water_bonds.html
A good starting point for those interested in learning more on this topic is:
http://www.vhan.nl/documents/ScientificReportECHNov04.pdf
The effect of high dilutions
In an experimental study of ultra-high dilutions of litihum chloride and sodium chloride which had been vigorously stirred between dilutions, researchers found emission of light even in dilutions beyond Avogadro’s number (10-30 g cm-3). The solutions were irradiated by x- and gamma-rays at 77 K, then progressively rewarmed to room temperature. Thermoluminescence was studied during the process.
Rey L. Thermoluminescence of ultra-high dilutions of lithium chloride and sodium chloride. Physica A 323 (2003) 67–74.
Full article available at
http://www.vhan.nl/documents/Rey.thermoluminescence.pdf
In another study of extremely diluted and succussed solutions (<>-5 mol kg-1, chemically identical to distilled water) researchers found that the diluted and succussed solution resulted in exothermic excess of heat (heat resulting from chemical reactions), higher electrical conductivity and pH compared to an untreated substance. The authors conclude that they show that successive dilutions and succussions can permanently alter the physico-chemical properties of the water solvent. The authors are unable to explain the phenomena.
Elia V, Niccoli M. New physico-chemical properties of extremely diluted aqueous solutions. Journal of Thermal Analysis and Calorimetry, Vol. 75 (2004) 815–836.
Abstract available at
http://grande.nal.usda.gov/ibids/index.php?mode2=detail&origin=ibids_references&therow=752081
Not really anything about research but a lovely example of homeopathy in action in a crisis.
http://pearlofhealth.blogspot.com/2007/06/dishwashing-liquid-youre-soaking-in-it.html