There has been a reported case of poisoning by herbal remedy. This has been discussed on the Bad Science forum and was also reported in an online news article that featured on Ben Goldacre’s Miniblog. I can’t see a report of this case on the herbal remedies page at whats the harm yet, but hopefully it will soon be up there – I’ve just submitted it. I’ve looked before at dubious herbal remedies and linked to some systematic reviews – like this one for individualised herbal medicine. The review is by R Guo, P H Canter and E Ernst and includes the following quote (my emphasis) –
Individualised herbal medicine, as practised in European medical herbalism, Chinese herbal medicine and Ayurvedic herbal medicine, has a very sparse evidence base and there is no convincing evidence that it is effective in any indication. Because of the high potential for adverse events and negative herb–herb and herb–drug interactions, this lack of evidence for effectiveness means that its use cannot be recommended.
Not only is there insufficient evidence that individualised herbal medicine is effective, but there is also a chance that the medicine(s) you take will be dangerous. Is it worth the risk?
UPDATE: http://depletedcranium.com/?p=491 has covered this story as well.