Comfrey
Symphytum, “grow together”; knitbone
- Known today as
- Symphytum officinale.
- Kind
- Plant, in 2 older authorities
- Constituents
- allantoin, symphytine, echimidine, and 1 more
- Earliest authority here
- Dioscorides (c. AD 40–90)
- In other databases
- Plants of the World Online search · GBIF search · Wikidata search
Revised October 1, 2026: Tradition, lore, modern assessment, and sources extended. Version 1, first published September 25, 2026.
Caution. Not to be taken by mouth.
Comfrey: what was it used for?
Poultices to knit broken bones and heal wounds; syrups for the lungs.
Comfrey: what does modern science say?
Its allantoin helps skin heal, but its pyrrolizidine alkaloids damage the liver; it is for the skin only. A controlled trial in 2004 found a comfrey root ointment eased sprained ankles as well as a standard anti-inflammatory gel. In 2001 the United States forbade its sale for internal use after cases of veno-occlusive disease of the liver, and most countries now limit even the ointment to unbroken skin for a few weeks a year.
Comfrey: is it poisonous?
Yes, in some form or dose. Not to be taken by mouth. Its poisoning is pyrrolizidine alkaloids (veno-occlusive disease): Weeks to months of use. Historical description, not medical advice; in a poisoning, call a poison centre.
Pharmacognosy & Toxicology
- Constituents
- allantoin ChEMBLpromotes the growth of skin
- symphytinea pyrrolizidine alkaloid
- echimidine ChEMBL
- rosmarinic acid ChEMBL
- Mechanism
- The alkaloids are converted in the liver to pyrroles that bind its DNA and proteins.
- Toxic dose
- Cumulative; cases from months of the tea.
- Syndrome
- Pyrrolizidine alkaloids (veno-occlusive disease)
- Standing
- Internal use withdrawn in the United States, where the FDA advised makers in 2001 to pull it from supplements, and barred in Germany, which allows only external products; the ointment allowed on unbroken skin for limited periods.
- Stickel, F., and Seitz, H. K. (2000). Public Health Nutrition 3. Book, not indexed
Constituent names open the compound’s record at PubChem, and “ChEMBL” beside a name opens its record at ChEMBL, the European Bioinformatics Institute’s database of bioactive molecules. Where a mechanism line was checked against ChEMBL (ChEMBL 37, read 1 October 2026), the check is shown with the measured value and its source paper, or says plainly that nothing has been measured. Doses are as the references give them, for description only; this is not medical advice. Each source carries the result of its check against Crossref, PubMed, or the authority’s page: see Verification.
Comfrey: what lore surrounds it?
Its country names, knitbone and boneset, record the use: the grated root, packed around a broken limb, set hard as it dried into a cast, and the mucilage gave the belief that the bone itself was being knitted. Henry Doubleday’s Russian comfrey of the 1950s was promoted as a wonder fodder and compost plant before its alkaloids were understood.
Comfrey: what did the older authorities say?
- Dioscorides
- Gives the root of symphyton, “the uniter,” for wounds and broken bones, and says the root is so glutinous that pieces of meat boiled with it grow together.
- Gerard
- Writes that the roots “glue together fresh wounds” and are good against ruptures and broken bones, a judgement every later herbal repeated.
Sources
- Dioscorides, De materia medica. Read in part · the text read
- Koll, R., et al. (2004). “Efficacy and tolerance of a comfrey root extract in the treatment of ankle distortion.” Phytomedicine 11. Verified against its record · doi:10.1016/j.phymed.2004.02.001
- Gerard, J. (1597). The Herball. Verified against its record · doi:10.5962/bhl.title.99400
Verification
- Checked
- October 1, 2026
- Passes
- Every sentence read against its sources, in the pass over the remaining 343 entries
- The Standing line checked against the authority it names (EMA, WHO, FDA, CITES, Commission E)
- Every dated or regulatory claim checked by category across the database
- Sources
- 4 cited: 1 read in part, 2 verified against its record, 1 book, not indexed. 1 with the abstract on file.
- Corrections
- "forbidden in the United States (2001) and Germany" overstated: the FDA advised manufacturers to withdraw it, and Germany allows external products only.
What was checked, how, and what was found is set out on the Verification page. A checked source is one whose record was found; it does not make the entry medical advice.
Cite This Entry
Version 1 · first published September 25, 2026 · last revised October 1, 2026
- Chicago
“Comfrey.” In Materia Medica, edited by B. C. P. Statema. Version 1. The Thinking Press, 2026–. Last modified October 1, 2026. https://thethinkingpress.org/materia-medica/comfrey.
- MLA
“Comfrey.” Materia Medica, edited by B. C. P. Statema, version 1, The Thinking Press, 1 Oct. 2026, thethinkingpress.org/materia-medica/comfrey. Accessed 8 Oct. 2026.
- APA
Comfrey. (2026, October 1). In B. C. P. Statema (Ed.), Materia medica (Version 1). The Thinking Press. Retrieved October 8, 2026, from https://thethinkingpress.org/materia-medica/comfrey
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See Also
Poisoned alike: pyrrolizidine alkaloids (veno-occlusive disease)
Houndstongue · Coltsfoot · Ragwort · Butterbur · Alkanet · Borage · the syndrome, with all of them →
Sharing allantoin, rosmarinic acid
Snail · Pulmonaria officinalis · Eryngium maritimum · Ocimum basilicum · Glechoma hederacea · Melissa officinalis
Also in Dioscorides
Crow’s gall in Dioscorides · Cuttlefish bone in Dioscorides · Chaste tree in Dioscorides · everything Dioscorides names →
Drawing on the same sources: Dioscorides, Gerard, Stickel
Colocynth · Horehound · Caesar’s mushroom · Lavender · Greater celandine · the bibliography →
Nearby in the alphabet
Common earthball (yellow-brown ball with a black interior, of acid woodland) · Common ink cap (A grey mushroom that dissolves into black ink as it ages) · Compound fumitory (Fumaria officinalis, with other herbs) · Coffee (The roasted seeds of Coffea arabica) · Concealed shoes · Cochineal (a parasite of the prickly-pear cactus of Mexico and South America)
Historical description, not medical advice.