Comfrey
Also called Symphytum officinale, comfrey root, Symphyti radix, Symphytum x uplandicum, knitbone.
Best grade B across 12 graded outcomes Botanical Last checked
The short answer
From 27 sourcesComfrey creams and ointments are applied to the skin for sprains, bruises and sore muscles and joints. Placebo-controlled trials of root-extract ointment found less pain and swelling in ankle sprains, acute back pain and knee arthritis (grade B), though most tested one of two branded products and were poorly reported. Comfrey contains liver-toxic pyrrolizidine alkaloids, so it is not eaten or drunk.
Every graded outcome on this page
12 rows · line = participants- BGrade BAcute back pain: comfrey plus methyl nicotinate vs methyl nicotinate aloneBack painn 379
- BGrade BPainful knee osteoarthritis (vs placebo)Jointsn 220
- BGrade BAnkle sprain pain: comfrey ointment vs diclofenac gelSprainsn 164
- BGrade BPain and swelling after an acute ankle sprain (vs placebo)Sprainsn 142
- BGrade BAcute upper or lower back pain (vs placebo)Back painn 120
- CGrade CTime for fresh abrasions to close: 10% vs 1% herb creamAbrasionsn 278
- CGrade CMuscle pain in the back: 10% vs 1% herb creamBack painn 215
- CGrade CAnkle sprain pain and function: 10% vs 1% herb creamSprainsn 203
- CGrade CAbrasion closure in children: 10% vs 1% herb creamAbrasionsn 108
- CGrade CKnee osteoarthritis pain, stiffness and function (blend creams)Jointsn 43
- DGrade DSkin reactions in children on intact or broken skinSkin tolerancen 712
- DGrade DPressure ulcer size and closure (uncontrolled study)Pressure ulcersn 151
- 9 more graded outcomes, in the evidence chapter
Key facts
- How it is used
- Only on the skin: ointments of comfrey root extract or creams of the aerial herb, rubbed in 3 to 4 times a day in the trials68917
- Strongest human evidence
- Ankle sprains (B): root-extract ointment beat placebo for pain and swelling (142 people) and was non-inferior to diclofenac gel (164 people)67
- Back pain
- In 120 people with acute upper or lower back pain, pain on movement fell about 95% with comfrey ointment vs 38% with placebo over 5 days (B)8
- Knee arthritis
- Cochrane: moderate evidence from one 220-person trial of a comfrey root extract ointment that it probably improves knee osteoarthritis pain, by 41.5 points on a 100-point scale310
- Why not by mouth
- Comfrey contains pyrrolizidine alkaloids that cause hepatic veno-occlusive disease and liver failure; LiverTox rates oral comfrey a probable cause of liver injury (likelihood score C), and in 2001 FDA advised supplement makers to remove comfrey products from the market16192624
What it is
Comfrey (Symphytum) is a plant used on the skin as root or herb extract creams for sprains, back pain and sore joints; it is not for eating.
How it works
ProposedComfrey herb and leaf contain allantoin and rosmarinic acid, and the plant also contains as many as 14 pyrrolizidine alkaloids, such as symphytine, lycopsamine and echimidine. When swallowed, the liver converts these alkaloids into reactive pyrroles that damage the small hepatic veins and DNA, causing veno-occlusive disease and, in rodents, liver tumours. How comfrey creams relieve pain and swelling, and how much alkaloid crosses intact skin, are not established in the sources here.41816
Forms side by side: root ointment, herb cream, blends and oral comfrey
4 forms named in our sources. The rest show what our data holds, and say plainly where it holds nothing yet.
Comfrey forms compared
4 forms| 4 forms | Root extract ointment | Herb (aerial parts) cream, 10% | With other actives (methyl nicotinate, or tannic acid and eucalyptus) | Tea, leaves, root or capsules taken by mouth |
|---|---|---|---|---|
| Absorption in people | Applied to intact skin over the painful area; skin absorption of its alkaloids is not established in these sources.4 | Applied to intact skin and, in children, to abrasions.15 | No head-to-head human data.11 | Swallowed pyrrolizidine alkaloids are activated in the liver to toxic pyrroles.1618 |
| Tolerance | No adverse drug reactions in the 8-day ankle trial; in the knee trial adverse events were 6% with comfrey vs 14% with placebo.63 | One burning and redness reaction among 712 children; no skin reactions in a 278-person abrasion trial.1520 | Two people per active group had temporary rash and itching with the tannic acid creams.14 | Hepatic veno-occlusive disease, including a fatal case, has been reported after comfrey leaves or tea.1916 |
| Studied for | Ankle sprains, acute back pain and knee osteoarthritis (B) | Ankle sprains, back muscle pain and abrasions (C, against a 1% cream) | Acute back pain (B) and knee osteoarthritis (C) | Not graded: oral use is unsafe, and in 2001 FDA advised supplement makers to remove comfrey products from the market |
- Comfrey root extract ointment
- Absorption in people
- Applied to intact skin over the painful area; skin absorption of its alkaloids is not established in these sources.4
- Tolerance
- No adverse drug reactions in the 8-day ankle trial; in the knee trial adverse events were 6% with comfrey vs 14% with placebo.63
- Studied for
- Ankle sprains, acute back pain and knee osteoarthritis (B)
- Comfrey herb (aerial parts) cream, 10%
- Comfrey with other actives (methyl nicotinate, or tannic acid and eucalyptus)
- Comfrey tea, leaves, root or capsules taken by mouth
- Absorption in people
- Swallowed pyrrolizidine alkaloids are activated in the liver to toxic pyrroles.1618
- Tolerance
- Hepatic veno-occlusive disease, including a fatal case, has been reported after comfrey leaves or tea.1916
- Studied for
- Not graded: oral use is unsafe, and in 2001 FDA advised supplement makers to remove comfrey products from the market
What the human research says
Human trials only, one row per outcome. The form line shows what each trial actually tested. Grades follow our evidence-grading policy.
Trial map
12 graded outcomes, largest study first12 graded outcomes: 11 improved, 1 no effect. The largest, a 2018 open-label trial of 712 people on skin reactions in children on intact or broken skin, found no effect.
1Skin reactions in children on intact or broken skin
No effect · Grade D · Open-label trial, 712 people, 2018
Children treated for blunt injuries and sports accidents: 386 with intact skin and 326 with abrasions or superficial wounds
Dose, result and source| Outcome | Found | People | Study | Who was studied |
|---|---|---|---|---|
| Skin reactions in children on intact or broken skin | No effect | 712 | Grade D · Open-label trial, 2018 | Children treated for blunt injuries and sports accidents: 386 with intact skin and 326 with abrasions or superficial wounds |
| Acute back pain: comfrey plus methyl nicotinate vs methyl nicotinate alone | Improved | 379 | Grade B · RCT, 2013 | Adults with acute upper or low back pain in a multicentre, three-arm trial |
| Time for fresh abrasions to close: 10% vs 1% herb cream | Improved | 278 | Grade C · RCT, 2007 | Patients with fresh abrasions, 64 of them aged 20 or younger |
| Painful knee osteoarthritis (vs placebo) | Improved | 220 | Grade B · RCT, 2007 | Adults with painful knee osteoarthritis (153 women, 67 men; mean age 57.9; symptoms for 6.5 years) |
| Muscle pain in the back: 10% vs 1% herb cream | Improved | 215 | Grade C · RCT, 2005 | Patients with myalgia in the lower and upper back |
| Ankle sprain pain and function: 10% vs 1% herb cream | Improved | 203 | Grade C · RCT, 2004 | Patients with acute ankle distortion in a multicentre trial |
| Ankle sprain pain: comfrey ointment vs diclofenac gel | Improved | 164 | Grade B · RCT, 2005 | Outpatients with an acute one-sided ankle sprain (mean age 29.0, 47.6% women) |
| Pressure ulcer size and closure (uncontrolled study) | Improved | 151 | Grade D · Open-label trial, 2014 | 161 patients with 198 pressure ulcers; 151 patients with 184 ulcers analysed per protocol |
| Pain and swelling after an acute ankle sprain (vs placebo) | Improved | 142 | Grade B · RCT, 2004 | Adults with an acute one-sided ankle sprain (mean age 31.8, 78.9% men) |
| Acute upper or lower back pain (vs placebo) | Improved | 120 | Grade B · RCT, 2010 | Adults with acute upper or lower back pain (mean age 36.9) |
| Abrasion closure in children: 10% vs 1% herb cream | Improved | 108 | Grade C · RCT, 2012 | Children aged 3 to 12 with fresh abrasions |
| Knee osteoarthritis pain, stiffness and function (blend creams) | Improved | 43 | Grade C · RCT, 2011 | Men and women aged 45 to 83 with primary knee osteoarthritis |
Every graded row
12 rowsShowing 12 of 12 outcomes. Human trials only.
BGrade BAcute back pain: comfrey plus methyl nicotinate vs methyl nicotinate aloneBack painCombination beat methyl nicotinate aloneRCT
n 379 · 2013
Improved Pain on movement (area under the curve) was markedly smaller with the combination than with methyl nicotinate alone or placebo (p < 0.0001); methyl nicotinate alone also had a considerable effect.
- Design
- RCT, n = 379, 2013
- Population
- Adults with acute upper or low back pain in a multicentre, three-arm trial
- Form
- Cream with 35% comfrey root extract and 1.2% methyl nicotinate vs 1.2% methyl nicotinate alone vs placebo
- Dose
- A 12 cm layer three times a day
- Duration
- 5 days
- Source
- Reference 11 · PubMed 22887778 (opens PubMed)
BGrade BPainful knee osteoarthritis (vs placebo)Joints−41.5 mm VAS vs placeboRCT
n 220 · 2007
Improved The pain score (VAS total) fell by 51.6 mm (54.7%) with comfrey vs 10.1 mm (10.7%) with placebo, a difference of 41.5 mm (95% CI 34.8 to 48.2). WOMAC scores, knee mobility and quality of life also improved more.
- Design
- RCT, n = 220, 2007
- Population
- Adults with painful knee osteoarthritis (153 women, 67 men; mean age 57.9; symptoms for 6.5 years)
- Form
- Comfrey root extract ointment (Kytta-Salbe f) vs placebo
- Dose
- 6 g a day (2 g three times a day)
- Duration
- 3 weeks
- Source
- Reference 10 · PubMed 17169543 (opens PubMed)
BGrade BAnkle sprain pain: comfrey ointment vs diclofenac gelSprainsNon-inferior to diclofenac gelRCT
n 164 · 2005
Improved Comfrey ointment was confirmed non-inferior to diclofenac gel for pain on pressure (the confidence interval lay entirely above the non-inferiority margin), and the primary and secondary results suggested it may be superior.
- Design
- RCT, n = 164, 2005
- Population
- Outpatients with an acute one-sided ankle sprain (mean age 29.0, 47.6% women)
- Form
- Comfrey root extract ointment (Kytta-Salbe f) vs diclofenac gel (1.16 g diclofenac diethylamine)
- Dose
- A 6 cm layer four times a day
- Duration
- 7 ± 1 days
- Source
- Reference 7 · PubMed 16323288 (opens PubMed)
BGrade BPain and swelling after an acute ankle sprain (vs placebo)SprainsLess pain and swelling vs placeboRCT
n 142 · 2004
Improved Comfrey was clearly superior to placebo for pain on pressure (p < 0.0001, primary outcome) and ankle swelling (p = 0.0001), and also for ankle mobility and global efficacy. No adverse drug reactions were reported.
- Design
- RCT, n = 142, 2004
- Population
- Adults with an acute one-sided ankle sprain (mean age 31.8, 78.9% men)
- Form
- Comfrey root extract ointment (Kytta-Salbe f) vs placebo ointment
- Dose
- Four applications a day
- Duration
- 8 days
- Source
- Reference 6 · PubMed 15500257 (opens PubMed)
BGrade BAcute upper or lower back pain (vs placebo)Back pain−95.2% vs −37.8% pain on movementRCT
n 120 · 2010
Improved Pain intensity on standardised movement fell by a median of about 95.2% with comfrey vs 37.8% with placebo, a significant difference that was consistent across all secondary measures; an effect was seen within 1 hour.
- Design
- RCT, n = 120, 2010
- Population
- Adults with acute upper or lower back pain (mean age 36.9)
- Form
- Comfrey root extract ointment vs placebo ointment
- Dose
- 4 g three times a day
- Duration
- 5 days
- Source
- Reference 8 · PubMed 19460762 (opens PubMed)
CGrade CTime for fresh abrasions to close: 10% vs 1% herb creamAbrasions4.08 vs 7.05 days to closureRCT
n 278 · 2007
Improved Wound size fell faster in the first 2 to 3 days (49% vs 29% a day), and estimated time to complete closure was 2.97 days shorter (4.08 vs 7.05 days). No skin reactions were seen.
- Design
- RCT, n = 278, 2007
- Population
- Patients with fresh abrasions, 64 of them aged 20 or younger
- Form
- Comfrey herb cream (Traumaplant 10%) vs an otherwise identical 1% cream
- Dose
- Topical cream as directed in the trial
- Duration
- 10-day observation
- Source
- Reference 20 · PubMed 18157595 (opens PubMed)
CGrade CMuscle pain in the back: 10% vs 1% herb creamBack painNNT 3.2RCT
n 215 · 2005
Improved Pain on movement, at rest and on palpation improved significantly more with the 10% cream; the number needed to treat was 3.2 and onset was faster. Tolerability was good to excellent.
- Design
- RCT, n = 215, 2005
- Population
- Patients with myalgia in the lower and upper back
- Form
- Comfrey herb cream (Traumaplant 10%) vs a 1% reference cream
- Dose
- Topical cream as directed in the trial
- Duration
- Not stated in the abstract
- Source
- Reference 12 · PubMed 16510384 (opens PubMed)
CGrade CAnkle sprain pain and function: 10% vs 1% herb creamSprains85.6% vs 65.7% good to excellentRCT
n 203 · 2004
Improved With the 10% cream, pain on movement, pain at rest and functional impairment fell significantly more than with the 1% cream on days 3 to 4 and day 7 (p < 0.001), and swelling improved more by day 3 to 4. Efficacy was rated good to excellent in 85.6% vs 65.7%.
- Design
- RCT, n = 203, 2004
- Population
- Patients with acute ankle distortion in a multicentre trial
- Form
- Comfrey herb cream (Traumaplant, 10% Symphytum × uplandicum pressed juice) vs a 1% version
- Dose
- Topical cream as directed in the trial
- Duration
- About 7 days
- Source
- Reference 9 · PubMed 15638067 (opens PubMed)
CGrade CAbrasion closure in children: 10% vs 1% herb creamAbrasions50% closure 0.9 days soonerRCT
n 108 · 2012
Improved A 50% closure rate was reached 0.9 days earlier with the 10% cream (rate 0.38 vs 0.26 a day, p = 0.0002), and physicians rated it good or very good more often. No adverse effects or skin irritation were reported.
- Design
- RCT, n = 108, 2012
- Population
- Children aged 3 to 12 with fresh abrasions
- Form
- Comfrey herb cream (Traumaplant 10%) vs a 1% version
- Dose
- Topical cream as directed in the trial
- Duration
- Until closure (assessed at days 2 to 3 and 7 to 9)
- Source
- Reference 13 · PubMed 22549241 (opens PubMed)
CGrade CKnee osteoarthritis pain, stiffness and function (blend creams)JointsBetter WOMAC pain, stiffness, functionRCT
n 43 · 2011
Improved Both comfrey creams beat the reference cream for WOMAC pain, stiffness and daily function (all P < .01). Two people in each active group had temporary rash and itching.
- Design
- RCT, n = 43, 2011
- Population
- Men and women aged 45 to 83 with primary knee osteoarthritis
- Form
- 10% or 20% comfrey root extract creams with tannic acid and eucalyptus vs a eucalyptus reference cream
- Dose
- Three times a day
- Duration
- 6 weeks
- Source
- Reference 14 · PubMed 22014903 (opens PubMed)
DGrade DSkin reactions in children on intact or broken skinSkin tolerance1 reaction in 712Open-label trial
n 712 · 2018
No effect No adverse events with intact skin; one burning and reddening reaction on broken skin. The rate of intolerance reactions was 0.14% (95% CI 0.00 to 0.78%) and of systemic adverse effects 0.00%.
- Design
- Open-label trial, n = 712, 2018
- Population
- Children treated for blunt injuries and sports accidents: 386 with intact skin and 326 with abrasions or superficial wounds
- Form
- Comfrey herb cream
- Dose
- 1 to 5 applications a day
- Duration
- Up to 2 weeks
- Source
- Reference 15 · PubMed 30805549 (opens PubMed)
DGrade DPressure ulcer size and closure (uncontrolled study)Pressure ulcers85.9% healed in 4 weeks (no control)Open-label trial
n 151 · 2014
Improved Complete healing within 4 weeks in 85.9% of treated ulcers per protocol (79.8% by intention to treat), and the total ulcer area fell by 89.2% over 25 to 30 days. Two cases of local irritation. There was no control group.
- Design
- Open-label trial, n = 151, 2014
- Population
- 161 patients with 198 pressure ulcers; 151 patients with 184 ulcers analysed per protocol
- Form
- Comfrey herb extract cream
- Dose
- Applied under dressings changed every 2 to 3 days
- Duration
- 4 weeks
- Source
- Reference 27 · PubMed 24048776 (opens PubMed)
What the numbers add up to
Each point is worked out from the data and the sources numbered on this page, with the arithmetic shown under it. It adds no new data and is not medical advice.
The knee result in context
A low-dose cream as the comparison
Studied doses
Doses used in research, shown against the official limits. They describe the studies, not a recommendation for you.
Studied doses in research, not advice. These are amounts used in research, not personal advice. Your clinician or pharmacist can say what fits you.
Doses studied in human trials
Doses studied in human trials ranged from a 6 cm layer of root ointment four times a day for about a week (ankle sprains) and 4 g three times a day for 5 days (back pain) to 2 g three times a day for 3 weeks (knee arthritis) and 10% to 20% root-extract creams three times a day for 6 weeks. Children with abrasions used a 10% herb cream 1 to 5 times a day for up to 2 weeks. These are research regimens on the skin, not product directions.78101415
When trials measured an effect
3 outcomes| Outcome | Measured at | Basis |
|---|---|---|
| Acute back pain | Effect seen within 1 hour; trial lasted 5 days | Placebo-controlled trial in 120 people8 |
| Ankle sprain pain and swelling | Days 3 to 4 and 7 to 8 | Placebo and low-dose controlled trials69 |
| Knee osteoarthritis pain | Measured at 3 weeks; the difference grew with treatment time | Placebo-controlled trial in 220 people10 |
Interactions and safety
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
What Comfrey meets
2 cited rowsMedicines 1
Supplements and foods 1
- Reference summary
Choose a medicine or supplement above to read its cited rows here.
Also cited:
Liver enzyme-inducing medicines
ReviewReference summary
Liver enzyme-inducing medicines, for example phenobarbital: LiverTox notes that enzyme inducers such as phenobarbital increase the toxicity of substances containing pyrrolizidine alkaloids, which the liver turns into toxic pyrroles; this matters if comfrey is swallowed.
Source 26, LiverTox (NCBI Bookshelf) (2022)
Other herbs with pyrrolizidine alkaloids
ReviewReference summary
Other herbs with pyrrolizidine alkaloids, for example coltsfoot, borage: Coltsfoot and borage also contain unsaturated pyrrolizidine alkaloids, the compounds behind comfrey's liver toxicity, so using them as well adds to the same exposure.
Source 23, Fitoterapia (2020); Source 16, Public Health Nutr (2000)
Interactions
2 agents| Agent | What the source says | Evidence |
|---|---|---|
| Medicines1 | ||
| Liver enzyme-inducing medicinese.g. phenobarbital | LiverTox notes that enzyme inducers such as phenobarbital increase the toxicity of substances containing pyrrolizidine alkaloids, which the liver turns into toxic pyrroles; this matters if comfrey is swallowed.26 | Review |
| Other supplements1 | ||
| Other herbs with pyrrolizidine alkaloidse.g. coltsfoot, borage | Coltsfoot and borage also contain unsaturated pyrrolizidine alkaloids, the compounds behind comfrey's liver toxicity, so using them as well adds to the same exposure.2316 | Review |
Check with what you take
Kept on this device onlyAdd what you take. We list every interaction our evidence profiles cite between Comfrey and your picks, and between your picks.
- Loading names…
Add a supplement or medicine you take to check it against Comfrey.
Starting from one medicine? The interaction checker rates how serious each pair is, on a curated list of 19 entries for 11 medicines. This cabinet has no severity rating: it lists every interaction row our supplement pages cite.
Who should be careful
7 groups- Anyone, by mouth
- Comfrey leaves, root and tea contain hepatotoxic pyrrolizidine alkaloids; case reports describe hepatic veno-occlusive disease and a death after eating comfrey leaves. In 2001 FDA told supplement makers that dietary supplements containing comfrey are adulterated and strongly recommended removing them from the market.191624
- Liver (LiverTox)
- LiverTox gives oral comfrey a likelihood score of C, a probable cause of clinically apparent liver injury through sinusoidal obstruction syndrome. Injury usually appears 1 to 2 months after starting comfrey tablets or large amounts of comfrey tea and can progress to acute liver failure.26
- Pregnancy
- The EU herbal monograph on comfrey root does not recommend it during pregnancy or breastfeeding: safety has not been established, and pyrrolizidine alkaloids isolated from the root showed reproductive toxicity in animal studies.25
- Breastfeeding
- LactMed says most sources consider topical comfrey contraindicated while breastfeeding; if it is used, only on intact skin away from the breast, on a small area, briefly, and the baby must not touch the skin where it was applied.4
- Broken skin
- Whether comfrey cream should go on broken skin is still debated by regulators; LactMed advises intact skin only, while an open study of 326 children with abrasions found one local reaction.154
Pyrrolizidine alkaloids: why comfrey stays on the skin
5 notesThe same plant that has positive skin trials is a known liver toxin when eaten.
- What is in it
- Comfrey contains up to 14 pyrrolizidine alkaloids, including symphytine, lycopsamine, intermedine and echimidine.18
- What they do when swallowed
- The liver turns them into reactive pyrroles that block small hepatic veins (veno-occlusive disease), which can lead to cirrhosis and liver failure; they are also genotoxic and caused liver tumours in rodents.1618
- Human cases
- A 23-year-old man died of liver failure from veno-occlusive disease after taking comfrey leaves; other reports describe the disease after comfrey tea. A 2020 review notes that species identification in many case reports is uncertain.19212223
- Regulators
- On July 6, 2001 FDA told supplement makers that dietary supplements containing comfrey are adulterated and strongly recommended removing them from the market; LiverTox notes that oral comfrey is banned or restricted in most countries while creams and ointments remain available. The EU herbal monograph on comfrey root does not recommend it in pregnancy or breastfeeding.242625
How to read the label
What to check on the Supplement Facts panel.
How to read the label
3 checksRoot or herb
For external use only
Frequently asked questions
Short answers to common questions; the numbers link to the sources below.
Common questions
8 answersDoes comfrey cream work for sprains?
Is comfrey good for back pain?
Does comfrey help knee arthritis?
Can you drink comfrey tea?
Can comfrey be used on open wounds?
Is comfrey safe on the skin?
What is the difference between comfrey root and comfrey herb creams?
Is comfrey banned?
Sources
27 sources: trial abstracts, NIH fact sheets and reference databases. Numbers in the text link here.
Sources cited on this page
27 sources- 1Comfrey: a clinical overview.Review Phytother Res, 2012 · PMID 22359388
- 2A critical scoping review of external uses of comfrey (Symphytum spp.).Systematic review Complement Ther Med, 2013 · PMID 24280482
- 3Topical herbal therapies for treating osteoarthritis.Systematic review Cochrane Database Syst Rev, 2013 · PMID 23728701
- 4Comfrey. Drugs and Lactation Database (LactMed).Database National Institute of Child Health and Human Development, 2021 · PMID 30000832
- 5Herbal Medicine for Low Back Pain: A Cochrane Review.Systematic review Spine, 2016 · PMID 26630428
- 6Efficacy 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.RCT Phytomedicine, 2004 · PMID 15500257
- 7Efficacy of a comfrey root extract ointment in comparison to a diclofenac gel in the treatment of ankle distortions: results of an observer-blind, randomized, multicenter study.RCT Phytomedicine, 2005 · PMID 16323288
- 8Efficacy 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.RCT Br J Sports Med, 2010 · PMID 19460762
- 9Efficacy and safety of topically applied Symphytum herb extract cream in the treatment of ankle distortion: results of a randomized controlled clinical double blind study.RCT Wien Med Wochenschr, 2004 · PMID 15638067
- 10Efficacy of a comfrey root (Symphyti offic. radix) extract ointment in the treatment of patients with painful osteoarthritis of the knee: results of a double-blind, randomised, bicenter, placebo-controlled trial.RCT Phytomedicine, 2007 · PMID 17169543
- 11Combination of comfrey root extract plus methyl nicotinate in patients with conditions of acute upper or low back pain: a multicentre randomised controlled trial.RCT Phytother Res, 2013 · PMID 22887778
- 12Topical symphytum herb concentrate cream against myalgia: a randomized controlled double-blind clinical study.RCT Adv Ther, 2005 · PMID 16510384
- 13Randomized double-blind study: wound-healing effects of a Symphytum herb extract cream (Symphytum×uplandicum Nyman) in children.RCT Arzneimittelforschung, 2012 · PMID 22549241
- 14Effect of a blend of comfrey root extract (Symphytum officinale L.) and tannic acid creams in the treatment of osteoarthritis of the knee: randomized, placebo-controlled, double-blind, multiclinical trials.RCT J Chiropr Med, 2011 · PMID 22014903
- 15Tolerability and effectiveness of an antitrauma cream with comfrey herb extract in pediatric use with application on intact and on broken skin.Open-label trial Int J Pediatr Adolesc Med, 2018 · PMID 30805549
- 16The efficacy and safety of comfrey.Review Public Health Nutr, 2000 · PMID 11276298
- 17Comfrey root: from tradition to modern clinical trials.Review Wien Med Wochenschr, 2013 · PMID 23224633
- 18Metabolism, genotoxicity, and carcinogenicity of comfrey.Review J Toxicol Environ Health B Crit Rev, 2010 · PMID 21170807
- 19Hepatic veno-occlusive disease associated with comfrey ingestion.Observational J Gastroenterol Hepatol, 1990 · PMID 2103401
- 20[Wound healing effects of a Symphytum herb extract cream (Symphytum x uplandicum NYMAN: ): results of a randomized, controlled double-blind study].RCT Wien Med Wochenschr, 2007 · PMID 18157595
- 21Comfrey herb tea-induced hepatic veno-occlusive disease.Observational Am J Med, 1989 · PMID 2741990
- 22Veno-occlusive disease of the liver secondary to ingestion of comfrey.Observational Br Med J (Clin Res Ed), 1987 · PMID 3115370
- 23A systematic review and quality assessment of case reports of adverse events for borage (Borago officinalis), coltsfoot (Tussilago farfara) and comfrey (Symphytum officinale).Systematic review Fitoterapia, 2020 · PMID 32105669
- 24FDA Advises Dietary Supplement Manufacturers to Remove Comfrey Products From the Market (letter of July 6, 2001)Safety communication U.S. Food and Drug Administration (archived page), 2001 · wayback.archive-it.org
- 25European Union herbal monograph on Symphytum officinale L., radix (EMA/HMPC/572846/2009 Corr1; adopted May 5, 2015, corrected January 31, 2024)Guideline European Medicines Agency, Committee on Herbal Medicinal Products, 2015 · ema.europa.eu
- 26ComfreyDatabase LiverTox (NCBI Bookshelf), 2022 · ncbi.nlm.nih.gov
- 27[Efficacy and safety of symphytum herb extract cream in the treatment of pressure ulcers].Open-label trial Z Gerontol Geriatr, 2014 · PMID 24048776
What changed
Every dated change to this page: what changed, who made it and why.
Change log
3 entries| Date | Change | Who and why |
|---|---|---|
| evidence, safety, interactions, FAQ | Audit: added the LiverTox comfrey entry (NBK548370, updated 2022; likelihood score C for oral use) as a liver note, to the oral-use key fact and the regulators note, and as the source for a new interaction (enzyme inducers such as phenobarbital increase pyrrolizidine alkaloid toxicity) and for infant susceptibility. Added a graded D row for an open, uncontrolled 4-week study of comfrey herb cream in 151 people with pressure ulcers (PMID 24048776). FAQ cut from 11 to 8: removed the diclofenac, breastfeeding, children and interactions items (the page's auto-derived questions and key facts already answer them) and added "Is comfrey banned?"; added three page questions. PubMed search for comfrey/Symphytum RCTs, meta-analyses and systematic reviews found nothing newer than 2020 that qualifies (a 2007 re-analysis of the diclofenac trial, PMID 18193693, reports the same 164 patients and was not added). FDA's 2001 comfrey advisory could not be re-opened today (fda.gov returns 404 at the old address; the archived copy did not load), so the existing citation, read on the archived page on 2026-10-19, is kept. Other interactions checked in LiverTox and LactMed: none further documented. | Writer: Kymata Health EditorialTrigger: A–Z audit against docs/supplements/AUDIT-STANDARD.md |
| all | New page. Every PMID checked with NCBI E-utilities (esummary title, year and journal) and its abstract read with efetch, including the LactMed record; two 1987 and 1989 case reports have no abstract and are cited by title for the event they report. FDA's 2001 comfrey advisory could not be retrieved, so the US status is attributed to LactMed. | Writer: Kymata Health EditorialTrigger: new page |
| safety | Review fixes: the knee trial is described as the ointment it tested (Cochrane's summary calls it a gel); the US status now cites FDA's own July 6, 2001 letter (read on FDA's archived page) as advice to remove comfrey supplements, instead of LactMed's "banned"; the 2000 review's "ban on distributing comfrey in Germany and Canada" is no longer repeated, since the topical ointments the trials tested are made and sold in Germany, so it cannot mean every comfrey product; a pregnancy caution is added from the EU herbal monograph (EMA/HMPC/572846/2009 Corr1, read as PDF); the forms table's tolerance row is labelled "Tolerance" (it covers creams and oral use). No evidence row or grade changed. | Writer: Kymata Health EditorialTrigger: adversarial review |
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