Comfrey grows natively in Europe and western Asia, and the roots and leaves are used in medicinal preparations. You might use topical remedies containing comfrey root extract to treat sprains, bruises, wounds, broken bones and more. Comfrey root contains some toxic substances that pose serious health risks, however, so you should talk with your doctor before using any remedy containing this herb.
Historically, herbalists used oral and topical remedies containing comfrey root to promote the healing of bones, earning the herb the Latin name Symphytum, meaning “drawing together,” and the common names knitbone and boneset. Herbalists also used creams made from comfrey root to apply topically to wounds, sprains or strains, bruises and varicose veins, says the University of Pittsburgh Medical Center. People also took the root orally to treat lung problems, stomach ulcers and other gastrointestinal problems, and an eyewash made from comfrey was used to treat eye problems and irritations, notes the University of Michigan Health System.