The root contains much higher levels than do the leaves or the flowers. Animal studies using amounts of coltsfoot hundreds of times higher than those used as medicine have shown these alkaloids can cause cancer in animals, but this is not applicable to the usual amounts of coltsfoot used as medicine. A single case of an infant who developed liver disease and died after the mother drank tea containing coltsfoot during pregnancy has been reported. This eventually led to the banning of coltsfoot in Germany in 1992. Leaf and flower preparations should not be taken for more than one month consecutively and root products should not be used internally.
Products guaranteed to be pyrrolizidine-free are preferable.
Coltsfoot should not be taken during pregnancy or lactation. Otherwise, coltsfoot is generally safe. Western coltsfoot should only be taken on the advice of a doctor knowledgeable in the use of botanical medicines. At the time of writing, there were no well-known drug interactions with coltsfoot. For the convenience of the reader, the information in the table listing the supplements for particular conditions is also categorized.