A professor Roger Byard, University of Adelaide, has suggested that some well known herbal medicines can be dangerous, even lethal, contrary to the perception that they are a safe alternative to conventional medicine.

The forensic pathologist said, "There's a false perception that herbal remedies are safer than manufactured medicines, when in fact many contain potentially lethal concentrations of arsenic, mercury and lead. These substances may cause serious illnesses, exacerbate pre-existing health problems or result in death, particularly if taken in excess or injected rather than ingested".

Forensic pathologist Roger Byard has reviewed the dangers linked to herbal medicines in last month's edition of the Journal of Forensic Sciences.

In addition, the expert has also cautioned against the risks arising from the interaction between herbal medicines and prescription drugs that could lead serious health hazards as liver, renal and cardiac failure, strokes, movement disorders, muscle weakness and seizures.

Professor Byard posted that a recent study of 251 Asian herbal products sold in California had discovered arsenic in 36, mercury in 35 and lead in 24. There were numerous incidents of young children developing lead or arsenic poisoning from traditional remedies.

He revealed that his interest in the area was triggered by the death of a young South Australian man in 2006 who had injected chan su, a traditional Chinese herbal remedy that contains toxic toad venom.