To the Editor: We wish to comment on the article by Whiting and colleagues1 on the proposed causal relationship between herbal remedies and severe acute hepatitis.

Investigators have found that reported adverse effects of herbal medicines are not, in fact, caused by herbs alleged to be in the product, but result from substitution or contamination of the declared ingredients, intentionally or by accident, with a more toxic herb, a poisonous metal or even a pharmaceutical compound.2,3

In reports of adverse effects, there is often no effort to establish a positive identification of the herb involved or any adulterants. The attribution of toxicity to the wrong plant leads to inaccurate information being provided to patients, practitioners and regulators.4

A significant problem is the use of common names. As mentioned by Whiting and colleagues,1 Cimicifuga racemosa (black cohosh) has at least 20 different common names, which can be very confusing. The most tragic example of such confusion is the fatal substitution of Stephania tetrandra by the toxic herb Aristolochia fangchi owing to the similarity of the common names of the two herbs.5

In recording and responding to adverse events involving herbs, certain key questions need to be asked by those reporting the event and, more crucially, by those subsequently citing the report. No details regarding verification of the herbal products taken by the individual patients were supplied by Whiting and colleagues.1 Because of this failure to authenticate the plant compounds in the preparations, one cannot establish that the herbs were the cause of the hepatotoxicity. No information about plant parts used, solvent, concentration, manufacturing process or chemical analysis was supplied.

Although Whiting et al exclude other causes for hepatitis, external factors may have contributed to the reported liver reactions. Hepatitis for which no cause can be identified is not uncommon.6 In addition, absence of hepatitis B surface antigen does not exclude the possibility of hepatitis B virus infection.7

The correlation of the liver diseases with preparations of Cimicifuga racemosa is speculative, as viral causes were not definitively ruled out. Without further pathophysiological or biochemical investigation, no conclusion can be made as to the exact mechanism.

In a review of eight human studies on the effectiveness of an extract of black cohosh for alleviating menopausal symptoms, the authors concluded that black cohosh appears to be a safe, effective alternative to oestrogen replacement therapy for patients in whom oestrogen replacement therapy is refused or contraindicated.8