The leaves, blossoms, and roots are ingredients in a large number of proprietary tea mixtures that are marketed in Europe for treating these conditions. Although coltsfoot contains mucilage, it can no longer be considered appropriate therapy for throat irritation. Pyrrolizidine alkaloids occur in the leaves and flowers, which render them carcinogenic. Neither the flowers, the leaves, nor the roots can safely be used for medicinal purposes. A hardy perennial with coarse, hairy leaves and variously colored bell-shaped flowers that bloom in late spring.
Common comfrey is native to Europe and grows in damp, grassy places.
In North America, it can be found in waste places from Newfoundland to Minnesota and South to Maryland. Comfrey is used in folk medicine in the form of an externally applied poultice for healing wounds. It is also taken internally as a tea or blended plant extract to heal stomach ulcers and to act as a ''blood purifier.'' Less-restrained advocates preach its virtues in treating cuts and wounds, burns, respiratory ailments of the lungs and bronchial passages, and ulcers of the bowels, stomach, liver, and gallbladder. Although comfrey was once enormously popular, its toxicity has been well-documented in recent years. The internal use of any species of comfrey should be avoided.