MUCH of the attraction of traditional medicines is that they are seen as natural and safe, in contrast to the powerful chemicals prescribed by ortho-dox doctors. Some herbs are gentle, harmless and safe; others are not. In particular, some Chinese herbal preparations may cause serious poisoning.

Late in 1994 a report appeared in the American journal Annals of Internal Medicine describing five cases in California of people who developed hepatitis after taking Jin Bu Huan, which has been used for more than 1,000 years to ease pain and help sleep. Two further cases were included from other parts of America. All had taken the herbal medicine in full dosage for several months before becoming ill. Symp-toms included loss of appetite, a sick feeling and loss of energy. Three of the seven were jaundiced. Tests showed the typical features of liver damage from drugs but no evidence of infection with hepatitis viruses .

Virtually conclusive evidence that the cause was the herbal product came when two patients, after recovering from their illness, took Jin Bu Huan again. Both quickly developed hepatitis once more.

Many drugs used in orthodox medicine may cause liver damage when taken in normal dosage: some tranquillisers, anaesthetics, antibiotics and oral contraceptives. Common drugs such as paracetamol cause liver damage when taken to excess. This report incriminating Jin Bu Huan is only the latest evidence that herbal preparations may also be hazardous: others that damage the liver include germander, chaparral, senna, mistletoe, skullcap, comfrey, and various herbal teas.

The final twist in the Jin Bu Huan cases was that analysis of the product showed the presence of a chemical found in the plants stephania and corydalis but not in polygala (the plant said to be the basis of the medicine in its packet). As the American journal noted: "the contents inside the Jin Bu Huan box were not Jin Bu Huan; the manufacturers either used the wrong plant or put wrong information on their package."

The fact that herbal medicines may cause unwanted side effects should not be surprising: effective remedies often do. Furthermore, many "chemical" drugs used today are based on herbal treatments. The pharmaceutical industry spends millions of pounds every year examining traditional remedies and attempting to extract the active ingredients in a chemically pure form, so that the substance concerned may be manufactured and marketed as a drug.

The reason the pharmaceutical industry prefers chemical drugs to traditional herbs is partly commercial (drugs can be patented) but mainly practical. It is very difficult for the herbalist to be certain of the strength of a traditional preparation. The amount of active chemical in seeds, pods or leaves is variable. Measuring the potency of herbal preparations requires chemical analysis or sometimes tests on animals, but these are not widely used.

Effective herbal preparations, like effective drugs, should be expected to be potentially dangerous. To believe otherwise is to believe in magic. But people who take traditional medicines should be able to expect standards of safety similar to those for prescription medicines. Herbalists often claim that their remedies have been proved safe for many years, but that does not guarantee the safety of an individual product bought in a high- street health food store.