[1][5][6] Its early common names, knitbone or boneset, reflect its historical use by poultices of leaves and roots to treat sprains, bruises or bone fractures.

Above ground the plant is covered in long, downward-pointing, tapering hairs that are bristly on the stems and softer on the leaves.

The flowers are radially symmetrical with five equal petals that are fused into a tubular or narrowly bell-shaped corolla with pointed, recurved teeth that are 2 mm long.

[7] With Symphytum × uplandicum, leaf bases are not decurrent, stem internodes are not winged, and the surfaces of the seeds are brown, dull, and finely granular instead of shiny black.

[15] Comfrey is found in moist grasslands or along riverbanks and ditches in western Asia, Europe, and North America.

[1][5][16] In 2001, the US Food and Drug Administration and Federal Trade Commission banned the sale of comfrey products for internal use and use on open wounds due to its potential toxicities.

[17][18] A 2018 review on pyrrolizidine alkaloids present in comfrey indicated widespread potential toxicity to humans and livestock, and the opportunity for drug development from these compounds.

[20] In folklore, Symphytum officinale roots were used in traditional medicine internally (as a herbal tea or tincture) or externally (as ointment, compresses, or alcoholic extract) for treatment of various disorders.

[1][6][21] John Gerard, an English herbalist (1545–1612), mentions "the slimie substance of the roote made in a possett of ale" would help back pains.

[1] A 2013 review of clinical studies assessing the possible effect of comfrey on osteoarthritis found the research quality was too low to allow conclusions about its efficacy and safety.

[22] In Europe as of 2015, there were no comfrey products for oral use, and those for topical uses to treat bruises or joint pain were evaluated as having risk of liver toxicity.