Herb & supplement monograph

Comfrey Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by ·Updated July 2026
What is this page for?

First and foremost: how Comfrey interacts with medications. The heart of this page is the interaction list — every drug Comfrey is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Comfrey is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Comfrey Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the risk of a clinically significant Comfrey drug interaction is moderate for most people, largely because comfrey itself can be hard on the liver. Every interaction on record is rated moderate, and all of them trace back to the same core concern: added stress on the liver.

Interactions deserving the most attention

Liver-harming (hepatotoxic) medications and enzyme-inducing drugs such as phenobarbital deserve the most attention. Comfrey contains pyrrolizidine alkaloids, compounds that can damage the liver, so combining it with other medicines that stress the liver could add to that harm. Certain drugs also speed up the enzyme the body uses to process these alkaloids, which converts them into more toxic forms, and case reports suggest this has worsened comfrey's toxicity.

What the rest of the list means

The long list of interacting medications reflects these two broad groups, not hundreds of separately proven problems. Most of the evidence is theoretical or based on limited reports rather than controlled human studies. Still, because liver harm is a known property of comfrey itself, the concern behind these interactions is real.

Check your medications against Comfrey

Based on HelloPharmacist’s Comfrey interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Comfrey

438 medications have a known interaction with Comfrey, graded by severity. Select any drug for the full evidence-based detail.

2,830 drugs
6-mercaptopurinePurinethol
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + 6-mercaptopurine interaction 6-mercaptopurine drug page: uses, dosage & side effects
Abacavir Sulfate, Dolutegravir, LamivudineTriumeq
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Abacavir Sulfate, Dolutegravir, Lamivudine interaction Abacavir Sulfate, Dolutegravir, Lamivudine drug page: uses, dosage & side effects
Abacavir, LamivudineEpzicom
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Abacavir, Lamivudine interaction
Abiraterone
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Abiraterone interaction Abiraterone drug page: uses, dosage & side effects
Abiraterone AcetateYonsa, Zytiga
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Abiraterone Acetate interaction Abiraterone Acetate drug page: uses, dosage & side effects
AcarboseGlucobay, Prandase, Precose
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acarbose interaction Acarbose drug page: uses, dosage & side effects
AcebutololRhotral, Sectral
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acebutolol interaction Acebutolol drug page: uses, dosage & side effects
AcetaminophenChildren's Tylenol, Children's Tylenol Meltaways, Tylenol, Tylenol Ex Strength
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen interaction Acetaminophen drug page: uses, dosage & side effects
Acetaminophen, AspirinGemnisyn
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Aspirin interaction
Acetaminophen, Aspirin, CaffeineExcedrin, Excedrin Extra Strength, Excedrin Migraine
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Aspirin, Caffeine interaction
Acetaminophen, Brompheniramine, PhenylpropanolamineDimetapp Cold and Flu
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Brompheniramine, Phenylpropanolamine interaction
Acetaminophen, ButalbitalAxocet, Bancap, Bucet, Butex Forte, Esgic CF, Orbivan CF +5 more
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Butalbital interaction
Acetaminophen, Butalbital, CaffeineEsgic, Esgic Plus, Fiogesic, Fioricet, Repan, Tecnal +1 more
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Butalbital, Caffeine interaction Acetaminophen, Butalbital, Caffeine drug page: uses, dosage & side effects
Acetaminophen, Butalbital, Caffeine, CodeineEsgic with Codeine, Fioricet w/ Codeine
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Butalbital, Caffeine, Codeine interaction
Acetaminophen, Butalbital, CodeineBancap w/ Codeine
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Butalbital, Codeine interaction
Acetaminophen, Butalbital, Codeine PhosphatePhrenilin #3
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Butalbital, Codeine Phosphate interaction
Acetaminophen, Caffeine, Chlorpheniramine, Hydrocodone, PhenylephrineHycomine Compound
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Caffeine, Chlorpheniramine, Hydrocodone, Phenylephrine interaction
Acetaminophen, Caffeine, CodeineGesic C15, Gesic C30, Gesic C8, Lenoltec 1, Lenoltec 2, Lenoltec 3 +1 more
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Caffeine, Codeine interaction
Acetaminophen, Caffeine, Codeine, SalicylamideCodalan No.1, Codalan No.2, Codalan No.3
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Caffeine, Codeine, Salicylamide interaction
Acetaminophen, Caffeine, DihydrocodeineDHC Plus, Panlor DC, Panlor SS
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Caffeine, Dihydrocodeine interaction
Acetaminophen, Caffeine, IsomethepteneMigralam
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Caffeine, Isometheptene interaction
Acetaminophen, Caffeine, PyrilamineMidol Max Strength Menstrual
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Caffeine, Pyrilamine interaction
Acetaminophen, Chlorpheniramine Maleate, Dextromethorphan HbrVicks Formula 44M Cough, Cold & Flu Relief
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Chlorpheniramine Maleate, Dextromethorphan Hbr interaction
Acetaminophen, Chlorpheniramine, Codeine, PhenylephrineColrex
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine interaction
Acetaminophen, Chlorpheniramine, DextromethorphanCoricidin II Extra Strength Cold and Flu
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Chlorpheniramine, Dextromethorphan interaction
Acetaminophen, Chlorpheniramine, Dextromethorphan HydrobromideCoricidin HBP Maximum Strength Flu
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Chlorpheniramine, Dextromethorphan Hydrobromide interaction
Acetaminophen, Chlorpheniramine, Dextromethorphan, PhenylpropanolamineMulti Symptom Cold Relief
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Chlorpheniramine, Dextromethorphan, Phenylpropanolamine interaction
Acetaminophen, Chlorpheniramine, Dextromethorphan, PseudoephedrineChildren's Tylenol Cold Plus Cough, Tylenol Cold Ex Strength
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Chlorpheniramine, Dextromethorphan, Pseudoephedrine interaction
Acetaminophen, Chlorpheniramine, Guaifenesin, Phenylephrine, SalicylamideRhinogesic GG
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Chlorpheniramine, Guaifenesin, Phenylephrine, Salicylamide interaction
Acetaminophen, Chlorpheniramine, PhenylephrineAlka-Seltzer PLUS, Histex SR, Protid
Moderate Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

Read the full Comfrey + Acetaminophen, Chlorpheniramine, Phenylephrine interaction
Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

  • Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
  • Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
  • Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
  • No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

  • Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
  • Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
  • Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

  • Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
  • Each drug listed above links to the full report for that exact Comfrey combination — clinical detail, likelihood, evidence level, and citations.
  • Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.
The big picture

The kinds of drugs Comfrey affects

Every type of medication (drug category) Comfrey is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 2 drug categories Comfrey interacts with
Cytochrome P450 3a4 (cyp3a4) InducersHepatotoxic Drugs
Cytochrome P450 3A4 (Cyp3A4) Inducers

Theoretically, CYP3A4 inducers might increase the risk of adverse effects from the pyrrolizidine alkaloid constituents in comfrey.
CYP3A4 enzymes convert pyrrolizidine alkaloids, constituents of comfrey, to toxic metabolites. Some case reports show that enzyme inducers, such as phenobarbital, seem to enhance the toxicity of comfrey.

Likelihood Possible Evidence D
Hepatotoxic Drugs

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.
Due to its pyrrolizidine alkaloid constituents, comfrey can cause hepatotoxic effects, including ascites, cirrhosis, hepatic fibrosis, hepatomegaly, and sinusoidal obstruction syndrome.

Likelihood Possible Evidence D
Monograph

Comfrey: Uses, Safety & Side Effects

Medically reviewed by · Reviewed July 2026 ·
The bottom line

Comfrey is a traditional herb used mainly on the skin for bruises, sprains, and joint pain, and some topical products show modest benefit for these uses. However, comfrey contains compounds that can seriously damage the liver, so it should never be taken by mouth and should only be used on unbroken skin for short periods. Pregnant or breastfeeding people should avoid it entirely.

Comfrey
Scientific name
Symphytum officinale
Family
Boraginaceae
Part used
Leaves and roots
Common forms
Topical ointments, creams, salves, poultices, and (less safely) teas
People commonly use it for
  • Bruises and sprains
  • Muscle and joint pain
  • Minor wounds and skin irritation
  • Back pain
  • Inflammation

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance
OverallUse caution

Topical use on unbroken skin for short periods may be acceptable, but oral use is unsafe due to liver toxicity.

PregnancyLikely Unsafe

When used orally or topically. In addition to hepatotoxicity and possible carcinogenicity, the pyrrolizidine alkaloids (PAs) in comfrey might be terat...

Read the full pregnancy detail
BreastfeedingLikely Unsafe

When used orally or topically. In addition to hepatotoxicity and possible carcinogenicity, the pyrrolizidine alkaloids (PAs) in comfrey might be terat...

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Comfrey (Symphytum officinale) is a leafy herb in the borage family. It is native to Europe and Asia and has spread to other parts of the world. The plant has large, hairy green leaves and small bell-shaped flowers that are often purple, pink, or cream-colored.

Comfrey has been used in folk medicine for centuries. People traditionally applied crushed leaves or root preparations to the skin to help with bruises, sprains, and aches. Some of its old nicknames, like "bruisewort" and "knitbone," reflect this history.

Today comfrey is most often found in topical products such as creams, ointments, and salves. Oral comfrey products are considered unsafe and have been pulled from the market in many countries.

How it works

Comfrey contains several compounds that may explain its traditional use. Allantoin is thought to support skin and tissue healing. Rosmarinic acid and other plant compounds may have anti-inflammatory effects, which could help with swelling and pain. The plant also contains mucilage, a slimy substance that may soothe tissue.

Much of what we know about these compounds comes from laboratory and animal research, so the exact way comfrey works in people is not fully proven.

Comfrey also contains pyrrolizidine alkaloids (PAs). These are natural compounds that can be toxic to the liver and are the main reason comfrey is considered dangerous when taken by mouth.

Effectiveness

Does Comfrey work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by .

Evidence overview · 14 uses evaluated
14 Insufficient evidence
How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.
2Likely EffectiveGood evidence, though not yet conclusive.
3Possibly EffectiveSome evidence suggests a benefit.
4Possibly IneffectiveSome evidence it may not help.
5Likely IneffectiveFairly strong evidence it doesn’t help.
6IneffectiveStrong evidence it doesn’t work.
7Insufficient Reliable Evidence to RateToo little research to say either way.

For Comfrey, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 14 conditions — evidence insufficient to rate
Insufficient Reliable Evidence To Rate Angina
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral comfrey for angina, there is insufficient reliable information about the clinical effects of comfrey for this purpose.

Insufficient Reliable Evidence To Rate Back pain
Rating & evidence shown verbatim from Natural Medicines

It is unclear if topical comfrey is beneficial in patients with back pain.

Insufficient Reliable Evidence To Rate Bronchitis
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral comfrey for bronchitis, there is insufficient reliable information about the clinical effects of comfrey for this purpose.

Insufficient Reliable Evidence To Rate Bruises
Rating & evidence shown verbatim from Natural Medicines

It is unclear if topical comfrey is beneficial in patients with bruises.

Insufficient Reliable Evidence To Rate Cancer
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral comfrey for cancer, there is insufficient reliable information about the clinical effects of comfrey for this purpose.

Insufficient Reliable Evidence To Rate Cough
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral comfrey for cough, there is insufficient reliable information about the clinical effects of comfrey for this purpose.

Insufficient Reliable Evidence To Rate Diarrhea
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral comfrey for diarrhea, there is insufficient reliable information about the clinical effects of comfrey for this purpose.

Insufficient Reliable Evidence To Rate Gastritis
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral comfrey for gastritis, there is insufficient reliable information about the clinical effects of comfrey for this purpose.

Insufficient Reliable Evidence To Rate Menorrhagia
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral comfrey for menorrhagia, there is insufficient reliable information about the clinical effects of comfrey for this purpose.

Insufficient Reliable Evidence To Rate Osteoarthritis
Rating & evidence shown verbatim from Natural Medicines

It is unclear if topical comfrey is beneficial in patients with osteoarthritis.

Insufficient Reliable Evidence To Rate Peptic ulcers
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral comfrey for peptic ulcers, there is insufficient reliable information about the clinical effects of comfrey for this purpose.

Insufficient Reliable Evidence To Rate Pharyngitis
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral or topical comfrey for pharyngitis, there is insufficient reliable information about the clinical effects of comfrey for this purpose.

Insufficient Reliable Evidence To Rate Sprains
Rating & evidence shown verbatim from Natural Medicines

It is unclear if topical comfrey is beneficial in patients with sprains.

Insufficient Reliable Evidence To Rate Tuberculosis
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral comfrey for tuberculosis, there is insufficient reliable information about the clinical effects of comfrey for this purpose.

Source & disclaimer. Effectiveness ratings and evidence summaries are provided by Natural Medicines (Therapeutic Research Center) and shown as licensed. Where Natural Medicines hasn’t rated a use, HelloPharmacist’s pharmacists may add their own reviewed rating and evidence (each such entry is labeled). This is educational information, not medical advice — talk with your pharmacist or doctor before starting, stopping, or changing a supplement.

Safety & precautions

The biggest safety concern with comfrey is its pyrrolizidine alkaloids, which can cause serious liver damage. Taking comfrey by mouth, using it in large amounts, or using it for long periods can be harmful and even life-threatening. For this reason, the FDA has advised that oral comfrey products be removed from the market.

If you use a topical comfrey product, follow these cautions:

  • Use it only on unbroken, healthy skin — not on open wounds, cuts, or damaged skin, since this can let harmful compounds enter the body.
  • Use it for short periods only, generally no more than a few weeks.
  • Look for products labeled free of pyrrolizidine alkaloids when possible.

Pregnant and breastfeeding people should avoid comfrey completely, including on the skin, because of the risk of liver toxicity and possible harm to the baby. Children and people with liver disease should also avoid it. When in doubt, talk to your pharmacist or doctor first.

Side effects

When used on the skin for a short time, comfrey is usually well tolerated, but it can cause skin irritation, redness, or allergic reactions in some people.

The most serious risk is liver damage, which is mainly linked to taking comfrey by mouth, using large amounts, applying it to broken skin, or using it for a long time. Warning signs of liver trouble can include yellowing of the skin or eyes, dark urine, belly pain, nausea, and unusual tiredness. Stop use and get medical care right away if these occur.

Comfrey: Reported Adverse Effects

Documented safety reports on Comfrey from the evidence-graded Natural Medicines (TRC Healthcare) database, shown word-for-word from the licensed record.

When used orally, comfrey may be unsafe. Topically, comfrey is generally well tolerated when applied to intact skin.

Most Common Adverse Effects:

Topically: Eczema, erythema, irritation, itching, rash.

Serious Adverse Effects (Rare):

All ROAs: Ascites, cirrhosis, death, hepatic fibrosis, hepatomegaly, pulmonary hypertension, and sinusoidal obstruction syndrome. These adverse effects are likely related to the pyrrolizidine alkaloid constituents of comfrey.

Reports by condition
Cirrhosis Hepatic

The pyrrolizidine alkaloid constituents of comfrey can cause acute sinusoidal obstruction syndrome characterized by sudden abdominal pain, vomiting, ascites, and hepatomegaly. In subacute disease, comfrey can cause ascites, hepatomegaly, abdominal pain, diarrhea, vomiting, and abdominal swelling. Chronic toxicity appears as asthenia and progressive ascites. Hepatic fibrosis and inflammation may resolve, but hepatic failure is common with more severe disease. This may occur as late as 2 years after the initial ingestion. Other signs and symptoms of pyrrolizidine toxicity include bile duct proliferation, fatty changes of the liver, fibrosis, cirrhosis, and vascular lesions. The mortality associated with comfrey toxicity is 50%. However, specific toxic levels seem to vary among individuals.

  1. Food and Drug Administration. FDA Advises Dietary Supplement Manufacturers to Remove Comfrey Products From the Market. July 6, 2001. Available at: http://www.cfsan.fda.gov/~dms/dspltr06.html.
  2. Stickel F, Seitz HK. The efficacy and safety of comfrey. Public Health Nutr 2000;3:501-8.
Diabetes Pulmonary/Respiratory

The pyrrolizidine alkaloid constituents of comfrey can damage the lungs, resulting in pulmonary hypertension. A case report involving a 66-year-old female with known arterial hypertension, mild kidney insufficiency, and type 2 diabetes described severe partial respiratory insufficiency and pulmonary hypertension. The patient admitted to using a number of alternative therapies daily, including comfrey.

  1. Stewart MJ, Steenkamp V. Pyrrolizidine poisoning: a neglected area in human toxicology. Ther Drug Monit 2001;23:698-708.
  2. Food and Drug Administration. FDA Advises Dietary Supplement Manufacturers to Remove Comfrey Products From the Market. July 6, 2001. Available at: http://www.cfsan.fda.gov/~dms/dspltr06.html.
  3. Stickel F, Seitz HK. The efficacy and safety of comfrey. Public Health Nutr 2000;3:501-8.
  4. Gyorik, S. and Stricker, H. Severe pulmonary hypertension possibly due to pyrrolizidine alkaloids in polyphytotherapy. Swiss.Med.Wkly. 4-4-2009;139(13-14):210-211.
Eczema Dermatologic

Topically, comfrey-containing creams and ointments may cause skin redness, irritation, itching, rash, and eczema.

  1. Predel, H. G., Giannetti, B., Koll, R., Bulitta, M., and Staiger, C. 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. Phytome
  2. Giannetti, B. M., Staiger, C., Bulitta, M., and Predel, H. G. 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. Br.J Spor
  3. Tanret, I. and Duh, D. [Pharmaceutical sheet. Symphytum officinale L., dermal use (Flexagile cream)]. J Pharm.Belg. 2012;(1):41-42.
  4. Laslett, L. L., Quinn, S. J., Darian-Smith, E., Kwok, M., Fedorova, T., Korner, H., Steels, E., March, L., and Jones, G. Treatment with 4Jointz reduces knee pain over 12 weeks of treatment in patients with clinical knee osteoarthritis: a randomised contr
  5. Frost R, Macpherson H, O'meara S. A critical scoping review of external uses of comfrey (Symphytum spp.). Complement Ther Med. 2013;21(6):724-45.
  6. Pabst H, Schaefer A, Staiger C, Junker-samek M, Predel HG. Combination of comfrey root extract plus methyl nicotinate in patients with conditions of acute upper or low back pain: a multicentre randomised controlled trial. Phytother Res. 2013;27(6):811-7.
  7. Smith DB, Jacobson BH. Effect 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. J Chiropr Med. 2011;10(3)
DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

Adverse-effects data: Natural Medicines, Therapeutic Research Center

Dosing

There is no well-established, standardized dose for comfrey, and oral use is not recommended at any dose because of liver toxicity.

For topical products, follow the directions on the product label and do not use more than directed or for longer than recommended (usually a few weeks at most). Because product strengths and formulas differ, it is best to check with your pharmacist or doctor before using comfrey, especially if you have any health conditions or take other medicines.

Pregnancy & Breastfeeding

Comfrey & Pregnancy

Likely Unsafe

When used orally or topically. In addition to hepatotoxicity and possible carcinogenicity, the pyrrolizidine alkaloids (PAs) in comfrey might be teratogenic. PAs are absorbed through the skin.

  1. Stewart MJ, Steenkamp V. Pyrrolizidine poisoning: a neglected area in human toxicology. Ther Drug Monit 2001;23:698-708.
  2. Food and Drug Administration. FDA Advises Dietary Supplement Manufacturers to Remove Comfrey Products From the Market. July 6, 2001. Available at: http://www.cfsan.fda.gov/~dms/dspltr06.html.
  3. Stickel F, Seitz HK. The efficacy and safety of comfrey. Public Health Nutr 2000;3:501-8.

Comfrey & Breastfeeding

Likely Unsafe

When used orally or topically. In addition to hepatotoxicity and possible carcinogenicity, the pyrrolizidine alkaloids (PAs) in comfrey might be teratogenic. PAs are absorbed through the skin.

  1. Stewart MJ, Steenkamp V. Pyrrolizidine poisoning: a neglected area in human toxicology. Ther Drug Monit 2001;23:698-708.
  2. Food and Drug Administration. FDA Advises Dietary Supplement Manufacturers to Remove Comfrey Products From the Market. July 6, 2001. Available at: http://www.cfsan.fda.gov/~dms/dspltr06.html.
  3. Stickel F, Seitz HK. The efficacy and safety of comfrey. Public Health Nutr 2000;3:501-8.
DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

© 2026 Therapeutic Research Center

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 13 references that drive our Comfrey monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Stewart MJ, Steenkamp V. Pyrrolizidine poisoning: a neglected area in human toxicology. Ther Drug Monit 2001;23:698-708. PubMed
  2. Food and Drug Administration. FDA Advises Dietary Supplement Manufacturers to Remove Comfrey Products From the Market. July 6, 2001. Available at: http://www.cfsan.fda.gov/~dms/dspltr06.html.
  3. Stickel F, Seitz HK. The efficacy and safety of comfrey. Public Health Nutr 2000;3:501-8. PubMed
  4. Chojkier M. Hepatic sinusoidal-obstruction syndrome: toxicity of pyrrolizidine alkaloids. J Hepatol 2003;39:437-46. PubMed
  5. Wang YP, Yan J, Fu PP, Chou MW. Human liver microsomal reduction of pyrrolizidine alkaloid N-oxides to form the corresponding carcinogenic parent alkaloid. Toxicol Lett 2005;155:411-20. PubMed
  6. Predel, H. G., Giannetti, B., Koll, R., Bulitta, M., and Staiger, C. 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. Phytome
  7. Gyorik, S. and Stricker, H. Severe pulmonary hypertension possibly due to pyrrolizidine alkaloids in polyphytotherapy. Swiss.Med.Wkly. 4-4-2009;139(13-14):210-211.
  8. Giannetti, B. M., Staiger, C., Bulitta, M., and Predel, H. G. 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. Br.J Spor PubMed
  9. Tanret, I. and Duh, D. [Pharmaceutical sheet. Symphytum officinale L., dermal use (Flexagile cream)]. J Pharm.Belg. 2012;(1):41-42.
  10. Laslett, L. L., Quinn, S. J., Darian-Smith, E., Kwok, M., Fedorova, T., Korner, H., Steels, E., March, L., and Jones, G. Treatment with 4Jointz reduces knee pain over 12 weeks of treatment in patients with clinical knee osteoarthritis: a randomised contr
  11. Frost R, Macpherson H, O'meara S. A critical scoping review of external uses of comfrey (Symphytum spp.). Complement Ther Med. 2013;21(6):724-45. PubMed
  12. Pabst H, Schaefer A, Staiger C, Junker-samek M, Predel HG. Combination of comfrey root extract plus methyl nicotinate in patients with conditions of acute upper or low back pain: a multicentre randomised controlled trial. Phytother Res. 2013;27(6):811-7. PubMed
  13. Smith DB, Jacobson BH. Effect 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. J Chiropr Med. 2011;10(3) PubMed
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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

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Brands that make products with Comfrey

10 brands in our database make a supplement containing Comfrey.

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Supplement products with Comfrey

29 products in our database contain Comfrey. Open any to see its full ingredient list and every drug interaction we check.

Pharmacist Counseling Corner

Comfrey: Common Questions

What is Comfrey used for, and does it work?
People use Comfrey for a range of reasons, but according to the Natural Medicines database the current clinical evidence is insufficient to confirm it works for the specific conditions it has been studied for. See the graded list on this page, and talk to your pharmacist or doctor before relying on it for any condition.
Does Comfrey interact with prescription medications?
Yes. We list 438 medications with a known interaction with Comfrey. Use the checker above to see how Comfrey interacts with a specific drug.
How are Comfrey interactions rated?
Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.
Is it safe to take Comfrey with my medications?
It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.
Where does this Comfrey interaction information come from?
Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.
What is Comfrey used for?
Comfrey is mostly used as a topical cream or ointment for bruises, sprains, and muscle or joint pain. Some studies suggest short-term benefit for these uses, but the evidence is limited.
Is it safe to take Comfrey by mouth?
No. Comfrey contains compounds that can cause serious liver damage, so it should not be swallowed. Regulators have advised removing oral Comfrey products from the market.
Can I use Comfrey while pregnant or breastfeeding?
No. Comfrey should be avoided during pregnancy and breastfeeding, including on the skin, because of the risk of liver toxicity and possible harm to the baby.
Can I put Comfrey on a cut or open wound?
It is best not to. Comfrey should only be applied to unbroken skin, because broken skin can let its toxic compounds enter the body more easily.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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