Basic science research

Homeopathic dilutions

Although the basic idea of homeopathy is similarity, its most controversial claim concerns the properties of ultra-molecular dilutions. Avogadro’s Constant, the number of particles (atoms or molecules) in a gram mole of a substance, is of the order of 1023. In homeopathic terminology, 1023 corresponds to a 23X or approximately 12C dilution. Homeopathic preparations in dilution less than those contain material traces of the original substance; those in high (ultra-molecular) dilution are unlikely to do so.

The ‘memory of water’ theory

The most widespread hypothesis to explain the mechanism of action of homeopathic dilutions refers to ‘memory of water’ effects: ‘Under appropriate circumstances, water retains information about substances with which it has previously been in contact and may then transmit that information to pre-sensitised biosystems’. Standard physico-chemical techniques,1-2 thermoluminescence,3-4 Raman and UV–VIS spectroscopy5-6 and other methods7have shown that water displays large changes in its physico-chemical properties as a function of its history. It remains to be proven whether such changes have the features to account for effects of homeopathic medicines in-vivo.8

Molecular clusters and other theories

An alternative mechanism is suggested by the results of research on molecular clustering in water solutions, which has shown 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.9  This means that residual molecular clusters of the original substance might 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.5

High-potency effects in biological experiments

A recent meta-analysis evaluated 67 in-vitro biological experiments in 75 research publications and found that high-potency effects were reported in nearly 75% of all replicated studies; however, no positive result was stable enough to be reproduced by all investigators.10 One example of a series of in-vitro experiments in homeopathy is the model of the allergic response to antibody using the human basophil degranulation test. The earliest study reported inhibition of degranulation with ultra-molecular dilutions of anti-IgE.11 These initial experiments did not prove to be reproducible.12, 13 Subsequent studies using a modified method, and using ultra-molecular dilutions of histamine, have shown positive results however. These findings have been reproduced in several independent laboratories,14, 15 as well as in a multi-centre series of experiments.16


1. Elia V, Niccoli M. Thermodynamics of extremely diluted aqueous solutions. Annals of the New York Academy of Sciences, 1999; 879: 241–248.

2. Elia V, Napoli E, Germano R. The “memory of water”: an almost deciphered enigma. Dissipative structures in extremely dilute aqueous solutions. Homeopathy, 2007; 96: 163–169.

3. Rey L. Thermoluminescence of ultra-high dilutions of lithium chloride and sodium chloride. Physica A, 2003; 323: 67–74.

4. Rey L. Can low temperature thermoluminescence cast light on the nature of ultra-high dilutions? Homeopathy, 2007; 96: 170–174.

5. Rao ML, Roy R, Bell IR, Hoover R. The defining role of structure (including epitaxy) in the plausibility of homeopathy. Homeopathy, 2007; 96: 175–182.

6. Roy R, Tiller WA, Bell IR, Hoover MR. The structure of liquid water; novel insights from materials research; potential relevance to homeopathy. Materials Research Innovations, 2005; 9-4: 577–608.

7. Vybíral B, Voráček P. Long term structural effects in water: Autothixotropy of water and its hysteresis. Homeopathy, 2007; 96: 183–188.

8. Chaplin M. The Memory of Water: an overview. Homeopathy, 2007; 96: 143–150.

9. Samal S, Geckeler KE. Unexpected solute aggregation in water on dilution. Chem Commun, 2001; 21: 2224–2225.

10. Witt CM, Bluth M, Albrecht H, et al. The in vitro evidence for an effect of high homeopathic potencies – A systematic review of the literature. Complementary Therapies in Medicine, 2007; 15: 128–138.

11. Davenas E, Beauvais F, Amara J, et al. Human basophil de-granulation triggered by very dilute antiserum against IgE, Nature, 1988; 333: 816–818.

12. Ovelgönne JH, Bol AW, Hop WC, van Wijk R. Mechanical agitation of very dilute antiserum against IgE has no effect on basophil staining properties. Experientia, 1992; 48: 504–508.

13. Hirst SJ, Hayes NA, Burridge J, et al. Human basophil degranulation is not triggered by very dilute antiserum against human IgE. Nature, 1993; 366: 525–527.

14. Belon P, Cumps J, Ennis M, et al. Inhibition of human basophil degranulation by successive histamine dilutions: results of a European multi-centre trial. Inflammation Research, 1999; 48 (Suppl 1): S17–S18.

15. Lorenz I, Schneider EM, Stolz P, et al. Sensitive flow cytometric method to test basophil activation influenced by homeopathic histamine dilution. Forschende Komplementärmedizin, 2003; 10: 316–324.

16. Belon P, Cumps J, Ennis M, et al. Histamine dilutions modulate basophil activation. Inflammation Research, 2004; 53: 181–188.