Comfrey, an old companion of gardens and damp woodland edges in Europe, owes its very name to its ancestral reputation for "knitting" bruised tissue back together. Since the Middle Ages, herbalists and countryfolk have used it as a poultice to support healing from bumps, sprains, and fractures, earning it the nickname "knitbone." Its mucilaginous root and broad, hairy leaves are still linked, in folk memory, to the care of the bruised body.
Comfrey was traditionally applied as a poultice on sprains, strains, and bruises, to accompany rest and recovery of the affected area.
For external use only, the leaves and root were said to help calm the appearance of minor superficial wounds and irritated skin.
Its folk name "knitbone" recalls its old use as a poultice for fractures, as a complement to — never a replacement for — proper medical care.
Herbalists of the past used compresses of root decoction on sore or swollen areas of the body.
External use only: comfrey contains pyrrolizidine alkaloids potentially toxic to the liver if ingested or applied to broken skin over a prolonged period. Internal use, and use on broken skin, is to be avoided entirely for pregnant or breastfeeding women and for young children. Never apply to a deep open wound or to a fracture not set by a healthcare professional. Consult a healthcare professional or a qualified herbalist before any use, particularly if taking other medication.
Partner herbalists — available with the detailed notebook.
PFAF, Wikipedia