The herb coltsfoot has a long history of use in the herbal medicine of Europe and Asia as a treatment for coughs and sore throats. It does not appear that traditional herbalists recognized that this treatment, which they often recommended for use by children, may cause liver damage.
Germany’s Commission E , the scientific body assigned to approving the use of herbal treatments in Germany, once approved coltsfoot for the treatment of sore throat. 1 However, coltsfoot was subsequently banned due to its content of potentially liver-toxic substances called pyrrolizidine alkaloids (see Safety Issues ). 2
Safety aside, there is no meaningful evidence that coltsfoot has any medicinal effects. Only double-blind, placebo-controlled trials can prove a treatment effective, and none have been reported for coltsfoot. (For information on why this type of study is essential, see Why Does This Database Rely on Double-blind Studies? ) Interestingly, much the same situation prevails for conventional cough syrups, none of which have been proven effective. 3 However, they at least appear to be safe.
Horticulturists have developed a form of coltsfoot that does not carry toxic pyrrolizidine alkaloids. 2 Products of this type, when available, should be safer. Nonetheless, since we don’t know whether coltsfoot offers any benefit, it’s not possible to state an effective dosage.
The pyrrolizidine alkaloids found in coltsfoot are known to have potential liver-toxic and cancer-promoting effects. One case report indicates that use of a coltsfoot tea caused severe liver problems in an infant that gradually disappeared when the tea was stopped. 4 In another case, an infant developed liver disease and died because the mother drank tea containing coltsfoot during her pregnancy. 5 Similar pyrrolizidine alkaloids are found in the herb comfrey, which has been associated with additional cases of liver injury. 6,7
Supporters of herbal therapy have defended the use of coltsfoot on the grounds that it was used for many thousands of years without harm. Unfortunately, there is a flaw in this reasoning. Traditional herbalists would be expected to notice immediate, dramatic reactions to herbal formulas, and one can assume with some confidence that treatments used for thousands of years are unlikely to cause such immediate problems in very many people who take them. However, certain types of harm could be expected to elude the detection of traditional herbalists. These include safety problems that are delayed, occur relatively rarely, or are difficult to detect without scientific instruments. How would a traditional herbalist ever know, for example, if a treatment caused liver failure in 1 out of 100,000 people who used it, especially if such failure took 2 or more years to develop? If such a death did occur in the herbalist’s patient population, it would probably be attributed to hepatitis or some other common cause. These factors may explain why traditional Chinese herbal medicine uses treatments that are now recognized as dangerous, such as mercury, arsenic, lead, and the kidney toxic herbs in the Aristolochia family.
Coltsfoot appears to fall into the same category. Most people can probably take coltsfoot for a short time and suffer no injury. A few people (especially infants), however, may have greater sensitivity and suffer harm. Many more people may experience harm if they use coltsfoot for a prolonged period of time.
For all these reasons, we strongly recommend against using coltsfoot.
1. Blumenthal M, Busse WR, Goldberg A, et al. (eds). The Complete German Commission E Monographs:Therapeutic Guide to Herbal Medicines . Austin: American Botanical Council and Boston: Integrative Medicine Communications; 1998:114–5.
2. Wawrosch C, Kopp B, Wiederfield H. Permanent monitoring of pyrrolizidine alkaloid content in micropropagated Tussilago farfara : a tool to fulfill statutory demands for the quality of coltsfoot in Austria and Germany. Acta Hort (ISHS). 2000;530:469–472.
Last reviewed September 2014 by EBSCO CAM Review Board
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