Toxic effects of herbal teas.

At least 26 herbal teas contain toxic ingredients, many of which have caused serious gastrointestinal, hematologic, cardiac, and nervous system disease. The severity of illness following herbal tea use has ranged from contact dermatitis to fulminant hepatic failure and death. Most of these teas are available in health food stores and there is no requirement that their toxic potential be labeled for consumer protection. Patients on anticoagulant drugs should avoid herbal teas containing coumarin.