Comfrey has been tied to at least seven cases of liver complications. Germander, touted by some herbalists as a weight loss aid, has been tied to 27 cases of liver inflammation and one death. Jin Bu Huan, an expensive Chinese patent medicine, has been tied to three cases of liver inflammation. Yohimbe, marketed as an aphrodisiac, has been tied to cases of kidney failure, seizure, and even death. A herbal preparation containing stephania and magnolia has been implicated in 48 cases of severe kidney injury.
Lobelia can suppress breathing, speed the heart, and possibly lead to coma or death.
It is highly advisable to look up all herbs in a modern Herbal guide, prior to use. Ma huang, used in products for weight control and enhanced energy, has been associated with memory loss, high blood pressure, and stroke. The FDA also warns that willow bark seems capable of producing adverse reactions, although to date none have been reported. Obviously if you are allergic to Aspirin, stay away from willow.