Herbal medicines and supplements can be beneficial. But, taken incorrectly, or in conjunction with other products, some can also have negative effects.

The Utah Poison Control Center says some herbs are more likely to produce toxic effects than others. Here is a list of "suspect" herbs, from the poison control center:

Could Cause Liver Damage:
- Borage
- Germander
- Chaparral
- Coltsfoot
- Life Root
- Comfrey

Could Increase Blood Pressure:
- Ephedra (Ma Huang) (see section on Ma Huang)
- Licorice

Could Cause Cancer:
- Calamus (non-North American)
- Sassafras

Could be Toxic to Gastrointestinal System:
- Pokeroot

Other Possible Reactions

In the publication, Medical Herbalism: A Journal for the Herbal Practitioner, Paul Bergner writes of three recent reports of possible drug-herb interactions:

Kava and Xanax: Kava is a recently-popular herb that has a relaxing effect, and is used as a treatment for anxiety. However, a recent report shows, "a patient apparently lapsed into a 'semicomatous state' due to an interaction between kava and the drug alprazolam (Xanax)." Therefore, Bergner suggests caution before using Kava with benzodiazepine drugs.

Gingko and blood thinners: Bergner writes, "Interactions between blood-thinning herbs and pharmaceutical medications with the same action present perhaps the greatest risk of drug-herb interactions in modern practice." That, he says, is due to the seriousness of the underlying condition that required the blood-thinner in the first place, and to the sensitive dose range, and serious side effects of the pharmaceutical blood-thinners. He says the risk is probably greatest with heparin, warfarin, and coumarin derivatives, but aspirin may pose a threat, as well. He cites a recent report in the New England Journal of Medicine about a case in which a patient who had been taking aspirin to prevent heart attack, reported spontaneous bleeding into the eye from the iris about a week after beginning daily doses of Gingko biloba. Two practitioners also reported to Bergner of patients with retinal hemorrhage after taking Gingko without other drugs.

Chinese Red Sage: Bergner cites a report of a rheumatic heart disease patient taking warfarin and the herb dan-shen, and suffering "dangerous abnormalities of clotting" as a probable result of the interaction. (Find the text of and references for Mr. Bergner's article at www.medherb.com)