Comfrey is a time-honored herb with a history of use that spans at least
2,000 years in southeast Asia. The plant was also widely used and
cultivated by Europeans, who introduced comfrey to the New World in the
17th century. Today, the herb is now distributed throughout much of
North America in pastures and wooded areas. It is also often grown as an
ornamental garden plant.
Although comfrey was used to produce teas and infusions for hundreds of
years, the presence of more than half a dozen pyrrolizidine alkaloids in
the leaf and root pose a risk of liver toxicity to animals and people.
The root, in fact, contains up to 16 times more pyrrolizidine alkaloids
than the leaf.
The traditional use of comfrey in topical formulations, however, is
supported by various tannins, rosmarinic acid and, most notably, a
compound called allantoin. The latter is used in the manufacture of
toothpaste, shampoo, sun screen lotions and other cosmetic and
pharmaceutical products.
