Tussilago farfara, commonly known as coltsfoot, is a plant in the family Asteraceae that has traditionally had medicinal uses. However, the discovery of toxic pyrrolizidine alkaloids in the plant has resulted in liver health concerns. T. farfara is the only species in the genus Tussilago. The name "tussilago" is derived from the Latin tussis, meaning cough, and ago, meaning to cast or to act on.
Coltsfoot is a perennial herbaceous plant that spreads by seeds and rhizomes. Tussilago is often found in colonies of dozens of plants. The flowers, which superficially resemble dandelions, appear in early spring before dandelions appear. The leaves, which resemble a colt's foot in cross section, do not appear usually until after the seeds are set. Thus, the flowers appear on stems with no apparent leaves, and the later appearing leaves then wither and die during the season without seeming to set flowers. The plant is typically 10–30 cm in height. The leaves have angular teeth on their margins.
Coltsfoot is native to several locations in Europe and Asia. It is also a common plant in North America and South America where it has been introduced, most likely by settlers as a medicinal item. The plant is often found in waste and disturbed places and along roadsides and paths. In some areas it is considered an invasive species.
In North America it occurs in the northeastern United States, the northwestern US state of Washington, southeastern Canada, the southwestern Canadian province of British Columbia, and the French overseas collectivity of Saint Pierre and Miquelon. The USDA Plants database indicates its presence in the US states of CT, DC, DE, IL, IN, KY, MA, MD, ME, MI, MN, NC, NH, NJ, NY, OH, PA, RI, TN, VA, VT, WA, WI, and WV, the Canadian provinces of BC, NB, NF, NS, ON, PE, and QC.
Other common names include tash plant, ass's foot, bull's foot, butterbur, coughwort (Old English), farfara, foal's foot, foalswort, horse foot and winter heliotrope. Sometimes it is confused with Petasites frigidus, or western coltsfoot.
Coltsfoot has been used in herbal medicine and has been consumed as a food product with some confectionery products, such as Coltsfoot Rock. Tussilago farfara leaves have been used in the traditional Austrian medicine internally (as tea or syrup) or externally (directly applied) for treatment of disorders of the respiratory tract, skin, locomotor system, viral infections, flu, colds, fever, rheumatism and gout.
Tussilago farfara contains tumorigenic pyrrolizidine alkaloids. Senecionine and senkirkine, present in coltsfoot, have the highest mutagenetic activity of any pyrrolozidine alkaloid, tested using Drosophila melanogaster to produce a comparative genotoxicity test. There are documented cases of coltsfoot tea causing severe liver problems in an infant, and in another case, an infant developed liver disease and died because the mother drank tea containing coltsfoot during her pregnancy. In response the German government banned the sale of coltsfoot. Clonal plants of colstfoot free of pyrrolizidine alkaloids were then developed in Austria and Germany. This has resulted in the development of the registered variety Tussilago farfara 'Wien' which has no detectable levels of these alkaloids.
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