Evidence review
Comfrey for Back Pain
Symphytum officinale
The short answer
Early or mixed evidencePossibly, for a few days of acute upper or lower back pain. One manufacturer-run trial in 120 people found a specific comfrey root ointment eased pain on movement far more than placebo over five days, which a Cochrane review rated low-quality evidence. A larger trial tested comfrey mixed with a warming ingredient, not comfrey alone. If you try it, use a licensed ointment on unbroken skin for a short course, never swallow comfrey, and keep moving.
6 key studies reviewed
Updated October 22, 2026
Key points
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01
One positive placebo-controlled trial
In 120 adults with acute upper or lower back pain, Kytta-Salbe f ointment cut pain on movement by a median of about 95% over five days, versus about 38% with placebo. The trial was run with the ointment’s maker.
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02
Rated low-quality evidence
A 2014 Cochrane review of herbal medicine for low back pain found low-quality evidence for comfrey, based on that single trial. Capsicum creams and willow bark had stronger evidence.
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03
Short-term, acute pain only
All the back pain trials lasted about five days and enrolled people with new, nonspecific back pain. Nothing is known about comfrey for chronic back pain, sciatica, or pain lasting weeks.
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04
Never swallow comfrey
Comfrey contains pyrrolizidine alkaloids that can cause severe liver damage when taken by mouth. The FDA told supplement makers to remove oral comfrey products in 2001.
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05
Unbroken skin, short courses
European rules limit comfrey root ointments to adults, unbroken skin, and no more than 10 days, and cap daily alkaloid exposure. Avoid it in pregnancy and breastfeeding.
A specific comfrey root ointment may ease a new bout of back pain, but the evidence comes down to one small, short trial. In 120 people with acute upper or lower back pain, an ointment called Kytta-Salbe f reduced pain on movement far more than a placebo (dummy) ointment over about five days. A larger trial found benefit from a cream combining comfrey with a warming ingredient, which makes it hard to tell how much came from the comfrey. A Cochrane review rated the evidence for comfrey as low quality, both trials were sponsored by or run with the product’s maker, and nobody has tested comfrey in back pain that lasts for months.
Most back pain is nonspecific, meaning it comes from the muscles, ligaments, and joints of the back rather than from a serious disease, and it usually improves within a few weeks. Comfrey (Symphytum officinale) is a borage-family plant long used in Europe as a poultice for bruises and sprains; its old name is knitbone. The root contains compounds that may calm inflammation, such as rosmarinic acid and allantoin, and also pyrrolizidine alkaloids, which can badly damage the liver when swallowed. For that reason comfrey is used today only on the skin, as licensed ointments made from extracts with the alkaloids reduced to very low levels.
This page covers the back pain trials and who ran them, how comfrey compares with the usual first steps for back pain, such as staying active and anti-inflammatory painkillers, how the tested products were used, and who should avoid comfrey. Nothing here is medical advice. Back pain with numbness around the genitals or buttocks, new bladder or bowel problems, leg weakness, fever, or a history of cancer needs a doctor, not an ointment.
02 The trials
Key studies
The trials and reviews that carry the most weight for this question, with the product and dose each one tested. Results apply to the preparation studied.
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Giannetti et al., 2010
Randomized, double-blind, placebo-controlled, multicenter trial (Germany)
- Who
- 120 adults with acute upper or lower back pain; mean age 36.9 years
- What and how much
- Kytta-Salbe f, a comfrey root extract ointment (35% extract, alkaloid content below 0.35 ppm), 4 g three times daily, versus placebo ointment
- How long
- 5 days (plus or minus 1 day)
Pain on standardized movement fell by a median of about 95.2% with comfrey and 37.8% with placebo, a significant difference in the main outcome; pain at rest, pressure pain, and global ratings also favored comfrey. Pain was lower after 1 hour (about 33% versus 12%). Adverse events were mild: four in the comfrey group and three with placebo. The paper declared no competing interests, but the corresponding author worked for Merck Selbstmedikation, which made Kytta products, and two authors worked for contract research firms.
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Pabst et al., 2013
Randomized, double-blind, three-arm, placebo-controlled, multicenter trial; manufacturer-sponsored
- Who
- 379 adults aged 18 to 45 with acute upper or low back pain, randomized 3:3:1
- What and how much
- Kytta-Balsam f (35% comfrey root extract plus 1.2% methyl nicotinate) versus 1.2% methyl nicotinate cream or placebo, about 4 g three times daily
- How long
- 5 days
The pain-on-movement score (area under the curve) was 50% lower with the combination than placebo and 27% lower than methyl nicotinate alone; methyl nicotinate alone was 31% lower than placebo. Application-site reactions occurred in 1.8% on the combination and 3.7% on methyl nicotinate. Sponsored by Merck Selbstmedikation; two authors were employees. The authors noted the placebo group could be small because people might detect placebo by the lack of skin reddening.
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Kucera et al., 2005
Randomized, double-blind, reference-controlled, multicenter trial with no placebo group
- Who
- 215 adults with muscle pain in the upper or lower back (Czech Republic)
- What and how much
- Traumaplant cream with 10% comfrey herb concentrate (Symphytum × uplandicum, Harras Pharma Curarina) versus the same cream at 1%
- How long
- Not stated in the published abstract
Pain on movement, pain at rest, and pain on pressure improved significantly more with the 10% cream than the 1% cream, with a calculated number needed to treat of 3.2 and faster onset. Tolerability was rated good to excellent. This tested a cream made from the leafy herb of Russian comfrey, not comfrey root, and compared two strengths rather than comfrey with placebo.
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Oltean et al., 2014 (Cochrane)
Systematic review of 14 randomized controlled trials of herbal medicines
- Who
- 2,050 adults with acute, subacute, or chronic nonspecific low back pain; 120 in the comfrey trial
- What and how much
- Herbal medicines including capsicum, devil’s claw, white willow bark, and Kytta-Salbe comfrey ointment
- How long
- Literature searched to September 2014
Found low-quality evidence, from one 120-person trial, that the Kytta-Salbe comfrey ointment beats placebo for short-term pain. Capsicum cream or plaster and willow bark extracts had moderate-quality evidence. No significant adverse events were seen. The authors called for larger trials against standard treatments and noted poor reporting.
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Frost et al., 2013
Critical scoping review of external comfrey use for any condition
- Who
- 26 studies: 13 randomized trials, 5 non-randomized trials, and 8 observational studies
- What and how much
- Topical comfrey preparations of several kinds
- How long
- Literature searched across 6 databases, 10 grey literature sources, and 9 trial registers
Individual trials showed benefit for ankle sprain, back pain, abrasion wounds, and osteoarthritis, but most trials had an unclear risk of bias because of poor reporting. Few adverse events were reported. Topical use appeared safe, but the University of York authors said more rigorous assessment is needed.
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Predel et al., 2005 (ankle sprain)
Randomized, observer-blind, multicenter non-inferiority trial; co-authored by Merck Selbstmedikation staff
- Who
- 164 outpatients with acute ankle sprain (not back pain)
- What and how much
- Kytta-Salbe f comfrey root ointment versus diclofenac gel, a topical NSAID, four times daily
- How long
- 7 days (plus or minus 1 day)
The comfrey ointment was non-inferior to diclofenac gel for pain on pressure, and the authors suggested it may be superior. It is the only head-to-head comparison of this ointment with a topical NSAID, and it was in sprained ankles, so it cannot be assumed to apply to back pain.
03 Evidence
What the research shows
Our rating for Comfrey for Back Pain, based on the studies below.
The key study is a randomized controlled trial by Giannetti and colleagues (British Journal of Sports Medicine 2010). At the German Sport University in Cologne and three outpatient centers, 120 adults with acute upper or lower back pain, average age 36.9, applied 4 g of either Kytta-Salbe f or a matching placebo ointment three times a day for about five days. The active ointment contained 35% of a comfrey root extract made with 60% ethanol, with pyrrolizidine alkaloids below 0.35 parts per million. The main outcome was pain during standardized movements, scored on a 100 mm visual analogue scale (a line on which patients mark how much it hurts) and added up over four visits. Pain on movement fell by a median of about 95% with comfrey and 38% with placebo, and pain at rest, sensitivity to pressure, and patients’ and doctors’ overall ratings all favored comfrey. Pain was already lower after one hour. Seven people reported mild adverse events, four on comfrey and three on placebo. The paper declared no competing interests, but the corresponding author, Christiane Staiger, worked for Merck Selbstmedikation, which made Kytta products, and the first and third authors worked for contract research companies.
A sister trial by Pabst and colleagues (Phytotherapy Research 2013), sponsored by Merck Selbstmedikation and designed with Germany’s medicines regulator, randomized 379 adults aged 18 to 45 with acute back pain. They used Kytta-Balsam f, which combines the same 35% comfrey root extract with 1.2% methyl nicotinate, a skin-reddening, warming ingredient; a cream with methyl nicotinate alone; or placebo, three times a day for five days. Pain on movement over the five days was 50% lower with the combination than with placebo and 27% lower than with methyl nicotinate alone, while methyl nicotinate alone was 31% lower than placebo. Rescue paracetamol (acetaminophen) was used by 9.2%, 5.5%, and 17.3% of the three groups. The design limits what this says about comfrey itself: only 52 people got placebo, deliberately, because the authors expected some to notice the lack of skin reddening, and the comfrey effect can only be inferred from the gap between the combination and methyl nicotinate alone. Two authors were Merck employees, and the trial excluded people with sciatica-type leg pain, recent injury, or chronic pain.
A third trial tested a different product. Kucera and colleagues (Advances in Therapy 2005) randomized 215 people with muscle pain in the upper or lower back to Traumaplant cream, made by Harras Pharma Curarina from the fresh leafy herb of Russian comfrey (Symphytum × uplandicum), at either 10% or 1% strength. Pain on movement, at rest, and on pressure improved significantly more with the 10% cream, and the authors calculated that about one extra person benefited for every three treated. There was no placebo group, the product is made from leaves rather than root, and the published abstract does not state how long treatment lasted or who funded the study. Outside back pain, the same Kytta-Salbe f ointment was compared with diclofenac gel, a topical nonsteroidal anti-inflammatory drug (NSAID), in 164 people with sprained ankles; Predel and colleagues (Phytomedicine 2005), writing with Merck staff, found the comfrey ointment was not inferior. No trial has compared comfrey with a topical or oral NSAID for back pain.
Independent reviewers are cautious. A Cochrane review by Oltean and colleagues (2014) of 14 trials of herbal medicines for low back pain, with 2,050 participants, found low-quality evidence from the single 120-person trial that Kytta-Salbe comfrey ointment improves short-term pain more than placebo. In the same review, capsicum cream or plaster and white willow bark extract had moderate-quality evidence. The authors said all these herbs seem to reduce pain more than placebo but called for larger trials against standard treatments, and noted that reporting in the trials was generally poor. A scoping review of external comfrey use by Frost and colleagues at the University of York (2013) found that most trials had an unclear risk of bias because of poor reporting, while few adverse events were reported. The European Medicines Agency (EMA) does not list back pain as a use for comfrey at all. Its monograph recognizes only the traditional use of a specified comfrey root preparation for minor sprains and bruises, and it set aside four clinical studies of a different comfrey preparation because their exact composition was not known.
Put together, the evidence supports comfrey ointment as a possible option for a few days of new, nonspecific back pain, but it does not show that comfrey beats usual care or helps chronic back pain. Every back pain trial lasted about five days, enrolled fairly young adults, and excluded people with nerve pain, so the results say nothing about sciatica, older adults, or pain that has lasted months. Most acute back pain improves over time whatever treatment is used, which is why the placebo groups also improved substantially. Laboratory studies suggest that rosmarinic acid and related compounds in comfrey root can dampen inflammatory signaling, which fits the trial findings, but how the ointment works in people has not been established. The important open questions are whether independent trials can reproduce the large effect seen in the manufacturer’s studies, and how comfrey compares with a topical NSAID gel in back pain.
04 In practice
How it was taken in studies
In the back pain trials, adults applied about 4 g of ointment, a strip of roughly 12 cm, to the painful area three times a day for about five days, rubbing it in gently. Licensed comfrey root ointments in Europe follow their own leaflets: the EMA monograph for its specified preparation calls for a thin layer twice a day for no more than 10 days, and advises seeing a doctor if symptoms persist or worsen. Follow the label of the product you buy, choose one that states it is made from a comfrey root extract with its pyrrolizidine alkaloid content controlled, and wash your hands after applying it. Homemade poultices, garden-leaf wraps, and infused oils have unknown alkaloid content and were not tested.
Comfrey should sit alongside the steps that guidelines recommend, not replace them. The NHS advises staying active and carrying on with daily activities, using heat or ice packs, gentle exercises and stretches, and anti-inflammatory painkillers such as ibuprofen if they suit you, while avoiding long spells in bed; it does not recommend paracetamol on its own. The UK’s National Institute for Health and Care Excellence (NICE) recommends advice to keep active, exercise programs, and oral NSAIDs at the lowest effective dose for the shortest time, and makes no recommendation about herbal creams. The American College of Physicians suggests starting with superficial heat, massage, acupuncture, or spinal manipulation for new low back pain, with NSAIDs or muscle relaxants if medicine is wanted. A comfrey ointment can be a reasonable add-on for someone who prefers not to take tablets or cannot take NSAIDs, provided they keep moving.
Judge it quickly. In the trials, people who responded felt a difference within hours to a few days, so if the pain is no better after about a week of use, there is little reason to continue, and the EMA limit of 10 days is a sensible ceiling. Back pain that has not improved after a few weeks of self-care, or that stops you doing your daily activities, deserves a review by a doctor or physiotherapist rather than more ointment. Using comfrey for months on a chronic back problem goes beyond anything that has been tested and beyond what European regulators allow.
05 Caution
Before you try comfrey
On unbroken skin, licensed comfrey root ointments were well tolerated in the back pain trials, with mild adverse events no more common than with placebo. Skin reactions are the main risk: an EMA review of European reports from 2015 to 2023 found 208 cases, mostly rash, itching, or redness, along with some allergic reactions and reports of breathlessness, and all seven serious cases involved a branded product with a special root extract outside the EMA monograph. Do not apply comfrey to broken, irritated, or inflamed skin, keep it away from the eyes and mucous membranes, and stop if a rash develops.
Never swallow comfrey in any form, including tea, capsules, tinctures, or leaves added to food. Its pyrrolizidine alkaloids are converted in the liver into toxic compounds that block the small veins of the liver, a condition called sinusoidal obstruction syndrome (formerly veno-occlusive disease). LiverTox, the US National Institutes of Health liver injury database, rates oral comfrey a probable cause of liver injury, typically starting one to two months after taking comfrey tablets or large amounts of tea, with abdominal pain, nausea, weight gain from fluid, and jaundice, and sometimes liver failure. In 2001 the US Food and Drug Administration (FDA) told supplement makers to remove comfrey products meant to be taken by mouth, and oral comfrey is banned or restricted in most countries. Far less passes through the skin: in a laboratory study on human skin, only 0.04–0.22% of a comfrey alkaloid applied in an ointment penetrated within 24 hours, but the EMA still limits daily alkaloid exposure from comfrey medicines to below 1 microgram, and broken skin absorbs more.
The EMA does not recommend comfrey root ointments for anyone under 18, or during pregnancy or breastfeeding, because safety has not been established and alkaloids from the plant have harmed developing animals in studies. No drug interactions have been reported for the ointment. People with liver disease, or who take medicines that can stress the liver, should ask a doctor or pharmacist before using it, since the liver is the organ at risk.
Some back pain needs medical care rather than any cream. Call 911 or go to an emergency department if back pain comes with numbness or tingling around the genitals, buttocks, or anus, new difficulty passing urine or loss of bladder or bowel control, weakness, numbness, or pain in both legs, chest pain, or if it started after a serious fall or accident; the first of these can signal cauda equina syndrome, a compression of the nerves at the base of the spine. Get an urgent appointment if you feel hot, shivery, or generally unwell, or the pain is severe, sudden, or quickly getting worse. See a doctor promptly if you have a history of cancer, have lost weight without trying, use steroids or inject drugs, or have pain that is worse lying down or wakes you at night. NICE asks clinicians to rule out cancer, infection, fracture, and inflammatory disease in these situations.
06 Questions
Frequently Asked Questions
It may help for a few days of new back pain. In one trial of 120 people, a specific comfrey root ointment, Kytta-Salbe f, reduced pain on movement by a median of about 95% over five days, compared with about 38% for placebo. A Cochrane review rated this low-quality evidence because it rests on a single trial, and that trial was run with the product’s maker. There is no evidence for comfrey in chronic back pain or sciatica.
A licensed comfrey root ointment used on unbroken skin for a short time is generally well tolerated; the back pain trials found mild side effects no more often than with placebo. Skin rash, itching, and redness can occur. European rules limit these products to adults, to no more than 10 days, and to a very low daily dose of pyrrolizidine alkaloids. Do not use it on broken or irritated skin, near the eyes, or during pregnancy or breastfeeding.
In the trials, adults applied about 4 g of ointment, roughly a 12 cm strip, three times a day for about five days, and some felt less pain within an hour. Licensed products have their own directions, often a thin layer twice daily, for no more than 10 days. Follow the leaflet, wash your hands afterward, and stop if there is no improvement after about a week. Keep moving and doing gentle exercise while you use it.
No. Comfrey contains pyrrolizidine alkaloids that can cause sinusoidal obstruction syndrome, a serious and sometimes fatal liver injury, when taken by mouth. The FDA told supplement makers to remove oral comfrey products in 2001, and oral comfrey is banned or restricted in most countries. Garden comfrey is no safer than bought products. If you want something to swallow for back pain, willow bark extract has better evidence for short-term low back pain, though it has its own cautions, including aspirin or NSAID allergy.
Nobody knows, because no trial has compared them in back pain. The only head-to-head trial, in 164 people with sprained ankles, found the same comfrey ointment was not inferior to diclofenac gel. NICE recommends considering oral anti-inflammatory painkillers such as ibuprofen for low back pain at the lowest dose for the shortest time, and the NHS lists them among first steps. Comfrey may suit people who cannot take NSAIDs, but it should not be assumed to work as well.
It is best not to. The European Medicines Agency does not recommend comfrey root ointments during pregnancy or breastfeeding, because safety has not been established and the plant’s alkaloids have harmed developing animals, or for anyone under 18. Back pain in pregnancy is common and worth discussing with a midwife or doctor, and back pain in a child or teenager deserves a medical check. Our guide to herbs for back pain includes pregnancy notes for each herb.
Capsicum creams and plasters made from cayenne peppers have the strongest evidence, rated moderate quality by Cochrane for chronic low back pain. White willow bark extract also has moderate-quality evidence for short-term pain, and devil’s claw has smaller, lower-quality trials. Arnica gels rest mainly on traditional use. Our guide to herbs for back pain compares them, and comfrey ointment has also been tested for knee joint pain.
07 References
Sources
These references support the claims on this page. They are not an endorsement of any product. The comfrey monograph carries its own full source list.
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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 19460762), 2010
Giannetti et al.: 120 patients, 4 g ointment or placebo three times daily for 5 days; pain on movement fell a median 95.2% versus 37.8%; corresponding author at Merck Selbstmedikation; competing interests declared as none.
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Combination of comfrey root extract plus methyl nicotinate in patients with conditions of acute upper or low back pain: a multicentre randomised controlled trial
Phytotherapy Research (PubMed 22887778), 2013
Pabst et al.: 379 patients aged 18–45; Kytta-Balsam f versus methyl nicotinate or placebo for 5 days; AUC 50% lower than placebo and 27% lower than methyl nicotinate; sponsored by Merck Selbstmedikation. Also describes the Giannetti trial product (35% extract, below 0.35 ppm alkaloids).
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Topical symphytum herb concentrate cream against myalgia: a randomized controlled double-blind clinical study
Advances in Therapy (PubMed 16510384), 2005
Kucera et al.: 215 patients with upper or lower back myalgia; Traumaplant 10% Symphytum × uplandicum herb cream versus 1% reference; significantly greater pain relief; number needed to treat 3.2.
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Herbal medicine for low-back pain
Cochrane Database of Systematic Reviews (PubMed 25536022), 2014
Oltean et al.: 14 RCTs, 2,050 participants; low-quality evidence from one 120-person trial that Kytta-Salbe comfrey ointment beats placebo for short-term pain; moderate-quality evidence for capsicum and white willow bark.
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A critical scoping review of external uses of comfrey (Symphytum spp.)
Complementary Therapies in Medicine (PubMed 24280482), 2013
Frost et al.: 26 studies; benefit in individual trials for ankle sprain, back pain, abrasions, and osteoarthritis; most trials at unclear risk of bias; few adverse events.
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Efficacy 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
Phytomedicine (PubMed 16323288), 2005
Predel et al.: 164 outpatients with ankle sprain; Kytta-Salbe f non-inferior to diclofenac gel over 7 days.
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Comfrey: a clinical overview
Phytotherapy Research (PubMed 22359388), 2012
Staiger (Merck Selbstmedikation employee): summarizes comfrey trials, including adverse events in the Giannetti trial (four mild events with comfrey, three with placebo).
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European Union herbal monograph on Symphytum officinale L., radix
European Medicines Agency (EMA/HMPC/572846/2009 Corr 1), 2024
Traditional use of a specified root extract for minor sprains and bruises only; thin layer twice daily, no more than 10 days; not under 18 or in pregnancy and lactation; not on broken skin; pyrrolizidine alkaloids below 1 µg/day.
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Addendum to Assessment report on Symphytum officinale L., radix
European Medicines Agency (EMA/HMPC/313662/2023), 2024
Periodic review: alkaloid limit raised from 0.35 to 1 µg/day; 208 EudraVigilance reports 2015–2023, mostly rash, itching, and redness; serious cases linked to a branded extract outside the monograph.
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Penetration of lycopsamine from a comfrey ointment through human epidermis
Regulatory Toxicology and Pharmacology (PubMed 27840092), 2017
Jedlinszki et al.: in a diffusion-cell study, 0.04–0.22% of the alkaloid lycopsamine penetrated human epidermis within 24 hours.
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Comfrey
LiverTox, National Institute of Diabetes and Digestive and Kidney Diseases (NIH), 2022
Oral comfrey a probable cause of sinusoidal obstruction syndrome (likelihood score C), usually within 1–2 months; oral forms banned or restricted in most countries; topical forms remain available.
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FDA Advises Dietary Supplement Manufacturers to Remove Comfrey Products From the Market
US Food and Drug Administration (archived copy), 2001
July 2001 letter: comfrey’s pyrrolizidine alkaloids are hepatotoxins; supplements containing comfrey are adulterated and should be removed from the market.
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Low back pain and sciatica in over 16s: assessment and management (NG59)
National Institute for Health and Care Excellence (NICE), 2016
Exclude cancer, infection, trauma, and inflammatory disease; advice to keep active and self-manage; group exercise; consider oral NSAIDs at the lowest dose for the shortest time; no paracetamol alone.
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Noninvasive Treatments for Acute, Subacute, and Chronic Low Back Pain: A Clinical Practice Guideline From the American College of Physicians
Annals of Internal Medicine (PubMed 28192789), 2017
Qaseem et al.: for acute low back pain, superficial heat, massage, acupuncture, or spinal manipulation first; NSAIDs or skeletal muscle relaxants if medicine is wanted.
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Back pain
NHS, 2026
Stay active, heat or ice, exercises, anti-inflammatory painkillers; emergency signs including numbness around the genitals or anus, bladder or bowel changes, leg weakness, and pain after a serious accident.
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Low back pain - acute
MedlinePlus, National Library of Medicine (NIH), 2026
Contact a provider right away for back pain with a history of cancer, unexplained fever, pain that wakes you at night or is worse lying down, or after a severe blow or fall; also with unintentional weight loss or steroid or injected drug use.