'The idea that like cures like is fanciful thinking'

The increasing popularity of homoeopathy is not matched by an acceptance in the scientific mainstream. Most doctors remain unconvinced that it can do any good for patients and some believe it can be positively harmful.

The increasing popularity of homoeopathy is not matched by an acceptance in the scientific mainstream. Most doctors remain unconvinced that it can do any good for patients and some believe it can be positively harmful.

Several studies published in the peer-reviewed scientific literature have suggested that certain homoeopathic treatments may benefit illnesses ranging from asthma to flu. None of them has provided unequivocal proof that homoeopathy really works.

Several, relatively small-scale, trials are cited by homoeopathists as evidence that the unconventional treatment with a highly diluted "medicine" - which can be toxic at normal concentrations - results in a definite improvement in symptoms.

One, published in the Journal of Clinical Pharmacology in 1989, showed that a homoeopathic treatment called oscillococcinum helped patients recover from influenza within 48 hours. Although the results were statistically significant, with 17 per cent of the 237 patients who took the treatment showing an improvement, the effect was still small when the placebo effect was taken into account - one in 10 placebo takers said their symptoms improved.

Homoeopathy is said to have been discovered in the early 19th century by a German doctor, Samuel Hahnemann, who formulated the basic principles of homoeopathy. The first is that "like cures like" - a drug that produces the same symptoms as the disease could be used to treat that illness. The second idea is the "minimum effective dose", which suggests that diluting the drug so it is almost certainly no longer present in the solution, the greater the potential it has to be a cure. Homoeopathists believe that by successively diluting a substance, it can leave behind an "imprint" in the water, which can impart a medicinal benefit.

Attempts have been made to pull together several of the relatively small-scale homoe-opathic studies into larger "meta-analyses", where conclusions are made on the basis of a wider source of data. These have been published in respected journals such as The Lancet and the British Medical Journal. A meta-analysis of homoeopathic studies of asthma and hay fever, published in The Lancet in 1994, found treatments were consistentlybetter than a placebo at improving patients' symptoms.

Vincent Marks, emeritus professor of clinical biochemistry at the University of Surrey, is one of the manyresearchers who remain unconvinced of the conclusions. One meta-analysis, Professor Marks said, showed a clinical benefit for heart patients if they took magnesium chloride but, when a proper clinical trial was done, the benefit proved non-existent.

"There is no convincing, double-blind study of homoeopathic treatments using large numbers of people with well-defined clinical end points where true benefits can be assessed," he said.

Another problem is that homoeopathy goes against conventional scientific wisdom. Professor Marks said: "The idea that 'like cures like' is fanciful thinking. Homoeopathy is a way of making the patient think you're doing something. In fact it defies the laws of physics and chemistry."