Comfrey: History and Traditional Use

Table of Contents

1. Botany, Range and a Name That Means "To Grow Together"
2. Dioscorides, Pliny and the Classical Wound Herb
3. Confirma, Consound and Knitbone: The Medieval and Early Modern Herbals
4. Poultice, Salve and Tea: How Comfrey Was Traditionally Used
5. Russian Comfrey: A Stamp-Gum Experiment Becomes a Movement
6. Allantoin and the "Cell Proliferant": The First Scientific Chapter
7. Pyrrolizidine Alkaloids and the First Liver Injuries (1968–1990)
8. Regulators Respond: Germany, Britain, the United States, Australia and the EU
9. Tradition Put to the Test: The Modern Topical Trials
10. Comfrey Today: Rub It On, Never Swallow It
11. Key Research Papers
12. Connections
13. Featured Videos

Botany, Range and a Name That Means "To Grow Together"

Common comfrey, Symphytum officinale, is a robust perennial of the borage family (Boraginaceae), a relative of borage and forget-me-not. It grows waist-high or taller from a thick root that is black or dark brown outside and white and slimy within, with large, bristly leaves and drooping clusters of bell-shaped flowers in cream, pink or purple. It is native to Europe and temperate western Asia and thrives in damp ground — river banks, ditches, wet meadows — which is exactly where the old herbals say to look for it. It has since naturalised across North America and much of the temperate world.

Two relatives matter for the story. Prickly comfrey, Symphytum asperum, comes from the Caucasus. Where the two species meet they hybridise, and the vigorous cross Symphytum × uplandicum is the plant the world knows as "Russian comfrey" — the one most modern gardeners grow, and the one at the centre of the twentieth-century enthusiasm described below. Old texts and many supplement labels do not distinguish between the species; the pyrrolizidine alkaloids that make comfrey dangerous to swallow occur in all of them.

The names are a history lesson in themselves. The Greek symphyton, Latinised as Symphytum, comes from symphyo, "I grow together" — a plant name that is really a therapeutic claim. The English word comfrey is usually traced through Middle English comferi and Old French cumfirie to a late Latin confervia, from confervere, "to boil together" or, in medical Latin, "to knit"; older herbalists preferred con firma, "made firm together." The medieval Latin consolida and confirma and the English "consound" say the same thing. Then come the country names — knitbone, boneset, bruisewort, blackwort, slippery root, gum plant, the Saxon yalluc — and the German Beinwell, from Bein, which originally meant bone. Almost every language has folded the idea of mending into its word for comfrey.

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Dioscorides, Pliny and the Classical Wound Herb

The earliest secure written record of comfrey comes from the two great first-century compendia of Greco-Roman medicine, written independently of each other within a few decades. Pedanius Dioscorides, a Greek physician who probably served with the Roman army, described symphyton in his De materia medica (written around 50–70 CE), noting roots "black on the outside and white and slimy on the inside." He recommended the ground root taken in drink for those "spitting blood" and for internal abscesses, and reported — in a phrase repeated for sixteen centuries — that the roots have a joining-together effect, so that pieces of flesh cooked with them were said to knit into one. An early English rendering gives his external use as roots "laid to" that are good "to glue together fresh wounds." Whether Dioscorides meant the pot-of-meat story literally or as a vivid picture of the root's mucilaginous, binding quality we cannot know; later herbalists took it literally.

Pliny the Elder (23–79 CE), compiling his encyclopaedic Naturalis historia at about the same time, lists comfrey among remedies for bruises and sprains and for the rapid healing of wounds — the two indications that, remarkably, modern European regulators still allow for the topical root — and repeats the belief that the herb makes meat cohere when boiled with it. Neither author was a systematic experimenter, but together they establish that by the first century comfrey was an ordinary part of the Mediterranean wound-healer's kit, used externally on injuries and, ominously in hindsight, internally as a drink. Through Arabic and Latin translations Dioscorides' account became the foundation of every medieval European description of comfrey.

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Confirma, Consound and Knitbone: The Medieval and Early Modern Herbals

One of the oldest surviving Latin herbals, the Herbarius attributed to "Pseudo-Apuleius" and compiled in about the fourth century from older sources, gives comfrey a chapter of its own under the double name herba confirma / simphitum. Copied in monasteries for the next thousand years — an Old English translation was made in Anglo-Saxon England — it kept comfrey in front of every literate healer in the West. Through the Middle Ages the plant appears as consolida, confirma and consound in Latin, French and English texts as a standard remedy for fractures, wounds, bruises and internal bleeding; historians of medicine summarise the period simply: in the Middle Ages comfrey was a famous remedy for broken bones. The names knitbone and boneset date from this long stretch of continuous use.

The printed herbals of the sixteenth and seventeenth centuries record the tradition at its height. John Gerard's Herball (London, 1597) affirmed, in words later quoted by the herbalist Maud Grieve, that a salve of the fresh herb "will certainly tend to promote the healing of bruised and broken parts," and offered comfrey in a compound remedy for ulcers of the lungs. Nicholas Culpeper (1616–1654), in The English Physitian of 1652 — the book that became Culpeper's Complete Herbal and has never been out of print — wrote that the roots are "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": Dioscorides' story, still alive after 1,600 years. Culpeper recommended comfrey for spitting and passing blood, inward wounds and bruises, the "bloody flux" (dysentery) and consumption, and said the root outwardly applied was "specially good for ruptures and broken bones."

Note what these authors were claiming: a binding, consolidating quality, inferred from the slimy root and the meat story, applied to wounds, sprains and fractures — and also given by mouth for bleeding and lung disease. The first practice would find partial support in clinical trials; the second would turn out to be the dangerous one, which is why this history cannot be told as a simple tale of ancient wisdom vindicated.

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Poultice, Salve and Tea: How Comfrey Was Traditionally Used

Across this long tradition the methods hardly changed. The classic preparation was the poultice: fresh root or leaf pounded to a pulp, sometimes warmed, bound over a bruise, sprain, swollen joint or closed fracture with a cloth and renewed once or twice a day. Grated comfrey root sets into a stiff, gummy mass as it dries — hence the old name "gum plant" — and country healers used that property to wrap a broken limb in pulp that hardened like a crude cast. Whether the plant or the immobilisation did the work is a question the tradition never asked.

The salve or ointment was the second great form: root or leaf simmered in lard, butter or oil, strained and kept in a pot for cuts, sores, chapped skin, ulcers and aching joints — Gerard's "salve of the fresh herb." Comfrey tea and decoction, leaf steeped or root boiled, were drunk for coughs, "spitting of blood," stomach and bowel complaints and as a general tonic; the mucilage (the slippery, gel-forming carbohydrate in the root) genuinely soothes an irritated throat or gut lining on contact, which helps explain why the practice persisted. Young leaves were eaten as a spring pot-herb and fed to animals.

All of these uses are tradition, not evidence of effect. The poultice and salve would later be tested and partly confirmed; drinking comfrey, and applying it to open wounds where the alkaloids can be absorbed, is the part modern toxicology has closed down. That distinction — on the skin versus into the body — was invisible to every generation before the 1970s.

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Russian Comfrey: A Stamp-Gum Experiment Becomes a Movement

Comfrey's modern career took an unexpected turn in Victorian Essex. Henry Doubleday (1810–1902), a Quaker smallholder, inventor and manufacturer of gum and gelatin at Coggeshall, held a contract to supply the gum arabic used on Britain's early postage stamps. Looking for a gum-yielding plant that could be grown in England instead of imported from Africa, he experimented with imported comfrey — the mucilaginous root looked promising — and, according to the organisation that now bears his name, obtained his stock from St Petersburg. The plant was the Caucasian hybrid now called Symphytum × uplandicum. As a source of stamp gum it failed. As a plant it fascinated him, and he is reported to have spent much of the rest of his life promoting it as a fodder crop and a food for a hungry world.

The idea lay dormant for half a century until the horticultural writer Lawrence D. Hills (1911–1990) rediscovered it. Researching his book Russian Comfrey (1953), Hills traced the plant to Doubleday and became convinced of its potential; in 1954 he founded the Henry Doubleday Research Association (HDRA) on a trial ground at Bocking, near Braintree in Essex. The strains he selected there — "Bocking 4" and above all "Bocking 14," which yields heavily and sets almost no viable seed, so it does not spread — are still the cultivars gardeners plant today. Into the 1970s the HDRA studied comfrey as animal feed, human food and medicine; in the 1980s, as the toxicology below became clear, its work shifted to comfrey's real excellence as a compost activator and liquid fertiliser. The HDRA is now Garden Organic and keeps the National Collection of comfrey at Ryton Gardens.

The movement matters to the medical history because it persuaded large numbers of people in Britain, North America, Australia and Japan to eat comfrey regularly as a health food — in salads, as a cooked green, in tablets and as daily tea. When the alkaloid findings arrived there was therefore a population of habitual consumers, and it was among them that the first human cases appeared.

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Allantoin and the "Cell Proliferant": The First Scientific Chapter

The compound that seemed to vindicate the knitbone legend had been known for a century before anyone connected it to comfrey. Allantoin, a small nitrogen-containing molecule, was first isolated in 1800 by the Italian physician Michele Buniva and the French chemist Louis-Nicolas Vauquelin; it was named in the 1820s for the allantoic fluid of the calf foetus in which it is abundant, and in 1837 Friedrich Wöhler and Justus von Liebig made it from uric acid. It is a natural product of purine breakdown in most mammals.

The comfrey connection was made in 1912. On 6 January the physician C. J. Macalister published in the British Medical Journal a paper titled "A new cell proliferant: its clinical application in the treatment of ulcers." Struck by reports of comfrey root poultices healing stubborn ulcers, he had the root analysed and found about 0.8 per cent allantoin; he then treated a series of chronic ulcers with dilute solutions of synthetic allantoin and reported rapid healing. His phrase "cell proliferant" entered the herbal literature at once: Maud Grieve's A Modern Herbal (1931) explains comfrey's reputation by allantoin's "powerful action in strengthening epithelial formations," and for the rest of the century allantoin was the standard scientific gloss on the name knitbone. The compound went on to a long career of its own in wound dressings and skin-care products.

Two cautions: Macalister's series was an uncontrolled case report, and later chemistry found other plausible actives in the root — rosmarinic acid and related anti-inflammatory compounds, and the mucilage itself — so "comfrey works because of allantoin" is a simplification. Still, 1912 is the moment comfrey entered the laboratory, and it entered on a hopeful note. The next chapter would not be hopeful.

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Pyrrolizidine Alkaloids and the First Liver Injuries (1968–1990)

Pyrrolizidine alkaloids (PAs) are a family of several hundred compounds that plants of the borage, daisy and pea families make as a defence against grazing. The dangerous members share a chemical feature (a double bond in their core ring) that the liver's own enzymes convert into highly reactive fragments; these attach to DNA and proteins in the small blood vessels of the liver, which swell and block. The result, hepatic veno-occlusive disease (now also called sinusoidal obstruction syndrome), produces a painful, enlarged liver, fluid in the abdomen and, in severe cases, liver failure. PAs were already known as the cause of ragwort poisoning in livestock and of human epidemics from contaminated grain; that comfrey belonged to the same chemical family was appreciated surprisingly late.

The alkaloids of Symphytum officinale were isolated and characterised by Furuya and Araki in 1968, in the first paper of a Japanese series on the constituents of crude drugs; they and later workers identified symphytine, echimidine, lycopsamine, intermedine and their acetylated forms, all of the hazardous unsaturated type, with the root carrying many times the concentration found in the leaf. In 1978 Hirono, Mori and Haga reported in the Journal of the National Cancer Institute that rats fed diets containing comfrey leaf or root developed liver tumours — hepatocellular adenomas in every dosed group, and blood-vessel tumours in some — establishing comfrey itself, not merely purified alkaloids, as carcinogenic in animals. In 1980 Claude Culvenor's group in Australia published the structures and toxicity of the alkaloids of Russian comfrey, the cultivar being promoted as a food, and said so in the title: "a medicinal herb and item of human diet."

Human cases followed. In April 1985 Paul Ridker and colleagues described in Gastroenterology a woman with hepatic veno-occlusive disease who had for months drunk comfrey tea and taken six comfrey-pepsin capsules a day; analysis of her capsules found pyrrolizidine alkaloids and their N-oxides. A British case was reported in the BMJ in 1987 (Weston and colleagues); in 1989 Bach, Thung and Schaffner described veno-occlusive disease from comfrey herb tea in the American Journal of Medicine, and Ridker wrote again in the Lancet and the Journal of Pediatrics, drawing attention to the risk from herbal teas in children; a further case was published in 1990. The numbers were never large — a few dozen well-documented cases worldwide, some fatal — but each combined a plausible exposure with a distinctive, otherwise rare liver lesion, and behind them stood the animal data. Because the alkaloids are genotoxic carcinogens, most toxicologists concluded that no safe oral intake could be defined.

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Regulators Respond: Germany, Britain, the United States, Australia and the EU

Germany moved first, and with nuance. Commission E, the expert panel that evaluated herbal medicines for the German health authority, published its comfrey root monograph on 27 July 1990: it approved Symphyti radix for external use only, for bruises, strains and sprains, describing its actions as anti-inflammatory and promoting callus (new bone) formation. On 5 June 1992 the Federal Health Office followed with a general rule for all PA-containing medicines: products could stay on the market only if daily exposure to the unsaturated alkaloids did not exceed 1 microgram for internal use or 100 micrograms for external use, and then for no more than six weeks a year. This ended oral comfrey medicines in Germany and pushed manufacturers toward the PA-depleted root extracts later used in clinical trials.

In the United Kingdom, the government's Committee on Toxicity reviewed the evidence and in 1993 concluded that there was sufficient evidence linking comfrey with toxic effects in humans; manufacturers and retailers were asked to withdraw products such as comfrey root tablets and capsules from sale. In Australia comfrey sits in Schedule 10 of the national Poisons Standard (substances whose sale and use are prohibited) for all preparations except those for use on the skin, which are in the lightly regulated Schedule 5; a 2023 review by the Therapeutic Goods Administration declined to change this. Canada likewise restricts comfrey to external use.

The United States acted in 2001. On 6 July the Food and Drug Administration wrote to the dietary-supplement trade associations advising that, because comfrey contains pyrrolizidine alkaloids associated with liver damage, it should not be used as an ingredient in supplements, and recommending that firms immediately stop marketing comfrey-containing supplements and tell consumers to stop using them. In the same month the Federal Trade Commission announced its second enforcement case against a supplement marketer over unsupported health claims for comfrey products sold for internal use. When the industry asked whether "PA-free" oral products might be acceptable, the FDA replied that it would expect any such product to be completely free of the alkaloids, not merely reduced, because no safe level had been established. The letter was advisory rather than a formal ban, but oral comfrey largely disappeared from reputable shelves.

The European Union completed the picture. The European Medicines Agency's herbal committee adopted a European Union herbal monograph for comfrey root on 5 June 2015, recognising it as a traditional herbal medicine for "the relief of symptoms of minor sprains and bruises" — Pliny's two indications — as a cream or ointment on intact skin, in adults only, for no more than ten days, with exposure capped at 0.35 micrograms of pyrrolizidine alkaloids a day. No internal use is recognised in any major pharmacopoeia.

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Tradition Put to the Test: The Modern Topical Trials

With the internal route closed, German researchers ran randomised, double-blind, controlled trials of comfrey root on the skin, using a standardised ointment made from a PA-depleted root extract. The results are the reason comfrey still has a place in medicine.

Koll and colleagues (2004) treated 142 adults with acute ankle sprains for eight days with comfrey root extract ointment or a placebo ointment and found significantly faster reductions in pain, swelling and tenderness with comfrey. Predel and colleagues (2005) compared the same ointment head-to-head with a diclofenac gel in 164 ankle sprains and found comfrey at least as effective. Grube and colleagues (2007) reported less pain and better mobility in 220 patients with knee osteoarthritis treated for three weeks. Giannetti and colleagues (2010), in the British Journal of Sports Medicine, randomised 120 patients with acute upper or lower back pain to comfrey ointment or placebo for five days and found a markedly greater fall in pain on movement in the comfrey group. Christiane Staiger's reviews of 2012 and 2013 gathered the whole literature and concluded that topical comfrey root extract has good evidence for short-term relief of pain, inflammation and swelling in muscle and joint injuries, with excellent tolerability.

Honest qualifications apply. Most of these trials tested one proprietary extract, were short, and were sponsored by its manufacturer, as is usual for licensed herbal medicines in Europe; independent replication is thin, and the trials say nothing about broken bones, open wounds or long-term use. The claim that comfrey speeds the healing of a fracture — the claim in its name — has never been tested in people and remains folklore. What the trials do show is that the humblest part of the tradition, the poultice on a sprain or a bruise, was pointing at something real.

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Comfrey Today: Rub It On, Never Swallow It

Comfrey's history resolves into an unusually clear present. On intact skin, for a few days at a time, standardised low-alkaloid creams and ointments are licensed traditional medicines across Europe and are supported by better trial evidence than most herbal products can claim. Taken by mouth in any form — tea, tablet, capsule, tincture, salad green — comfrey is an established liver toxin and animal carcinogen whose sale for ingestion is prohibited or advised against by the regulators of Germany, the United Kingdom, the United States, Canada, Australia and the European Union. Broken skin, children, pregnancy and home-made preparations of unknown alkaloid content all fall on the wrong side of that line. The plant's other modern life, as the organic gardener's compost activator and liquid feed, carries no such risk.

The modern verdict — a good herb to rub on and a dangerous one to swallow — is not a rejection of the tradition but its refinement: two thousand years of poultices were partly right, and a century of chemistry has explained both why they helped and why the tea should never have been drunk.

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Key Research Papers

The list below gathers the scientific landmarks of comfrey's history — the 1912 allantoin paper, the isolation of the alkaloids, the animal carcinogenicity study, the first human case reports and the modern topical trials — together with the principal reviews. Historical primary texts (Dioscorides, Pliny, the Pseudo-Apuleius Herbarius, Gerard and Culpeper) are named in the article rather than cited here.

1. Macalister CJ (1912). A new cell proliferant: its clinical application in the treatment of ulcers. BMJ. — doi:10.1136/bmj.1.2662.10
2. Furuya T, Araki K (1968). Studies on constituents of crude drugs. I. Alkaloids of Symphytum officinale Linn. Chemical and Pharmaceutical Bulletin. — doi:10.1248/cpb.16.2512
3. Hirono I, Mori H, Haga M (1978). Carcinogenic activity of Symphytum officinale. Journal of the National Cancer Institute. — PubMed PMID: 278864
4. Culvenor CC, Clarke M, Edgar JA, et al. (1980). Structure and toxicity of the alkaloids of Russian comfrey (Symphytum × uplandicum Nyman), a medicinal herb and item of human diet. Experientia. — PubMed PMID: 7379906
5. Ridker PM, Ohkuma S, McDermott WV, Trey C, Huxtable RJ (1985). Hepatic venocclusive disease associated with the consumption of pyrrolizidine-containing dietary supplements. Gastroenterology. — PubMed PMID: 3972224
6. Bach N, Thung SN, Schaffner F (1989). Comfrey herb tea-induced hepatic veno-occlusive disease. The American Journal of Medicine. — PubMed PMID: 2741990
7. Stickel F, Seitz HK (2000). The efficacy and safety of comfrey. Public Health Nutrition. — PubMed PMID: 11276298
8. Koll R, Buhr M, Dieter R, et al. (2004). Efficacy and tolerance of a comfrey root extract (Extr. Rad. Symphyti) in the treatment of ankle distorsions: results of a multicenter, randomized, placebo-controlled, double-blind study. Phytomedicine. — PubMed PMID: 15500257
9. Giannetti BM, Staiger C, Bulitta M, Predel HG (2010). Efficacy and safety of comfrey root extract ointment in the treatment of acute upper or lower back pain: results of a double-blind, randomised, placebo controlled, multicentre trial. British Journal of Sports Medicine. — PubMed PMID: 19460762
10. Staiger C (2012). Comfrey: a clinical overview. Phytotherapy Research. — PubMed PMID: 22359388

PubMed Topic Searches

1. PubMed: Comfrey ethnobotany and traditional use
2. PubMed: Comfrey pyrrolizidine alkaloids and veno-occlusive disease
3. PubMed: Comfrey root ointment randomised trials

External Authoritative Resources

• European Medicines Agency — Symphyti radix (comfrey root) EU herbal monograph, 2015
• NIH LiverTox — Comfrey
• US National Toxicology Program — Comfrey and its alkaloids: background review
• Federal Trade Commission — July 2001 action on comfrey products (references the FDA letter of 6 July 2001)
• Garden Organic (formerly HDRA) — Comfrey history: Doubleday, Hills and Bocking 14
• NCCIH — Herbs at a Glance

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Connections

• All Herbs
• Comfrey Hub
• Comfrey Benefits
• Never Take Comfrey Internally
• Wound Healing and Allantoin
• Arnica
• Calendula
• Yarrow
• Plantain Herb
• Coltsfoot
• Ankle Sprain
• Low Back Pain
• Osteoarthritis
• Liver Injury from Supplements

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