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Herb library · Herb · Symphytum officinale

Comfrey

A hairy, broad-leaved plant nicknamed knitbone, rubbed on as an ointment for sprains, bruises and sore joints. Several trials of comfrey root ointment suggest it eases pain, but taken by mouth it can cause severe liver injury, and the FDA advised removing oral comfrey products from the market in 2001.

Serious warning

Taken by mouth, comfrey can cause severe liver injury. LiverTox reports cases of sinusoidal obstruction syndrome from comfrey tablets and large amounts of comfrey tea, caused by the pyrrolizidine alkaloids it contains; in 2001 the FDA advised dietary supplement manufacturers to remove comfrey products from the market.

Traditional use

Native to Europe and Asia and now found worldwide. Its roots and leaves have long been used for wounds, bruises, sprains, broken bones and the pain of arthritis; old herbals also gave the root by mouth for coughs and bleeding. LiverTox notes that oral comfrey is now banned or restricted in most countries, while ointments, creams and liniments are still sold for wounds, sprains and fractures. In the European Union, comfrey root ointments are registered as traditional herbal medicines for minor sprains and bruises, a status based on long-standing use.

Traditional energetics

What studies show

  • Limited

    Knee osteoarthritis: a 2013 Cochrane review found moderate-quality evidence from a single trial of 220 people that a comfrey extract gel probably eases pain, with side effects no more common than placebo. One trial is not enough to be sure.

  • Limited

    Sprains and back pain: placebo-controlled trials of a comfrey root ointment in 142 people with ankle sprains (2004) and 120 people with acute upper or lower back pain (2010) found less pain than with placebo. Each finding rests on one trial of one product.

  • Insufficient

    Taking comfrey by mouth for any use: not supported, and unsafe because of its liver toxicity.

Be careful of

Cautions

  • NoteDo not swallow comfrey in any form: tea, root powder, capsules or tablets. LiverTox says liver injury usually appears 1 to 2 months after starting, with pain under the right ribs, nausea, weight gain from fluid, and then jaundice.
  • ConditionLiverTox notes that infants appear to be especially sensitive to pyrrolizidine alkaloid injury, and the EMA does not recommend comfrey ointment for anyone under 18. Keep comfrey products away from children.
  • InteractionDrugs that speed up liver enzymes, such as phenobarbital, increase the toxicity of these alkaloids (LiverTox).
  • AmountThe amount of pyrrolizidine alkaloid varies with the part of the plant, its age and when it was harvested, so strength differs from product to product.
  • NoteOn the skin: the EMA says not to apply it to broken or irritated skin, to keep it away from the eyes and mouth, and not to use it for more than 10 days.
  • PregnancySafety in pregnancy and breastfeeding has not been established; its isolated alkaloids have caused reproductive toxicity in animals, and the EMA does not recommend it then, even on the skin.
  • Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.

From the old books

What herbals and dispensaries of the past printed. History, in their words.

“yea, it is said to be so powerful to consolidate and knit together, that if they be boiled with dissevered pieces of flesh in a pot, it will join them together again.”
Nicholas Culpeper, Culpeper's Complete Herbal (1814), p. 54. See the page of Culpeper's Complete Herbal, p. 54 (opens in a new tab) · Read the full passage from Culpeper's Complete Herbal, p. 54
“The root is medicinal; when fresh it is glabrous, fusiform, branching, 10 or 12 inches in length, by 1 in diameter, and very mucilaginous.”
Harvey Wickes Felter and John Uri Lloyd, King's American Dispensatory (1905), vol. 2, p. 1870. See the page of King's American Dispensatory, vol. 2, p. 1870 (opens in a new tab) · Read the full passage from King's American Dispensatory, vol. 2, p. 1870

Sources

  1. European Union herbal monograph on Symphytum officinale L., radix (opens in a new tab) · EMA · read September 25, 2026
  2. Comfrey (LiverTox) (opens in a new tab) · NIH · read September 25, 2026
  3. Dietary Supplements Guidance Documents & Regulatory Information (opens in a new tab) · FDA · read September 25, 2026
  4. Topical herbal therapies for treating osteoarthritis (Cochrane Database Syst Rev, 2013) (opens in a new tab) · NIH · read September 25, 2026
  5. Efficacy and tolerance of a comfrey root extract in the treatment of ankle distorsions (Phytomedicine, 2004) (opens in a new tab) · NIH · read September 25, 2026
  6. Efficacy and safety of comfrey root extract ointment in the treatment of acute upper or lower back pain (Br J Sports Med, 2010) (opens in a new tab) · NIH · read September 25, 2026

Reviewed September 25, 2026.