Comfrey – please don’t use it

28th January 2015
Beryl Shuttleworth
50 Responses

Even today, years after pyrrolizidine alkaloids were found and identified in Comfrey (aka Symphytum officinale), herbalists continue to recommend its use. A few years ago, after I had commented on an online site about the dangers of using Comfrey, a well-known animal herbalist called me on the phone. “Comfrey isn’t dangerous”, she told me. “It is just a scam by Big Pharma to stop us using it so that they can make more money.”

It isn’t a scam by Big Pharma. Comfrey can kill. Pyrrolizidine alkaloids are very toxic to the liver and are also carcinogenic (cause cancer). The way that they work is by blocking small blood vessels in the liver. This leads to cirrhosis and eventually liver failure. In humans, use of comfrey for as little as 5 days (in children) or 19 days (in adults) has resulted in severe liver damage and death. Even long term use of very small doses can be harmful, as the damage is cumulative and the damage is irreversible.

Generally speaking, the root has higher levels of these molecules than the leaves. Also, some of Symphytum officinale’s close relatives (commonly mistaken for Comfrey) have even higher levels.

What about topical (skin) use? Pyrrolizidine alkaloids can be absorbed through the skin as well. So, if you’re going to use a cream or ointment, make sure that the daily amount applied to the skin doesn’t exceed 100 micrograms. You might find that it is difficult to ascertain the correct level as most preparations don’t put the amount onto the label. Also, the analytical method used to assay these compounds is a bit unreliable.

Both the leaves and the roots of Comfrey have been shown to cause cancer. Rats fed Comfrey (0.5% roots and 8% leaves) developed hepatomas (liver cancer) and died.

What are the symptoms of pyrrolizidine alkaloid poisoning?

  • jaundiced skin (from impaired liver function)
  • rough unkempt appearance
  • diarrhoea
  • prolapsed rectum
  • oedema of tissues of the digestive tract
  • dullness
  • photosensitization
  • abnormal behaviour. Horses may have neurological signs such as “head pressing”
  • cattle may have a bloated appearance

If you want my honest opinion, rather avoid Comfrey and any products containing it, altogether.


  1. Williams L, Chou MW, Yan J, et al. Toxicokinetics of riddelliine, a carcinogenic pyrrolizidine alkaloid, and metabolites in rats and mice. Toxicol Appl Pharmacol. 2002;182:98-104.
  2. Mei N, Guo L, Fu PP, et al. Mutagenicity of comfrey ( Symphytum officinale) in rat liver. Br J Cancer. 2005;92:873-5.
  3. Stickel F, Seitz HK. The efficacy and safety of comfrey. Public Health Nutr. 2000;3:501-8.
  4. Couet CE, Crews C, Hanley AB. Analysis, separation, and bioassay of pyrrolizidine alkaloids from comfrey ( Symphytum officinale). Nat Toxins. 1996;4:163-7.
  5. Winship KA. Toxicity of comfrey. Adverse Drug React Toxicol Rev. 1991;10:47-59.
  6. Betz JM, Eppley RM, Taylor WC, et al. Determination of pyrrolizidine alkaloids in commercial comfrey products ( Symphytum sp.). J Pharm Sci. 1994;83:649-53.
  7. Yeong ML, Wakefield SJ, Ford HC. Hepatocyte membrane injury and bleb formation following low dose comfrey toxicity in rats. Int J Exp Pathol. 1993;74:211-7.
  8. Yeong ML, Clark SP, Waring JM, et al. The effects of comfrey derived pyrrolizidine alkaloids on rat liver. Pathology. 1991;23:35-8.
More about this article
Comfrey - please don't use it
Comfrey - please don't use it
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50 Responses

  1. Hi Beryl, What we should understand is that the use of Comfrey as a feed stock goes back for many years. Comfrey can be used safely by any human and animal that has been introduced to it slowly in order for the user to develop the necessary microbiome in the gut to digest it properly.
    Therefore you can understand that any reference to tests with lab rats , or tests with humans having the chemicals injected into them makes no sense, because there is no natural process involved in the metabolizing of the chemicals. The body will get sick of any chemical that you simply inject into the bloodstream.
    Futhermore, instances where animals could get sick is when they get into a patch of comfrey, while they have been feeding on other feeds, and they built up a hunger for something else. The same thing happens when animals go into a land with Alfalfa, and they blow up of the feed. Comfrey is also very high in aminoacids, and can cause adverse reactions like Alfalfa.
    Any animal or human that is not adapted to certain chemicals will get sick of it. Take for instance people smoking near you. Absolutely horrendous!


  2. After reading this article I freaked out a bit as I have been treating my 1.5 yr old daughter mosquito bites and bruises with comfrey cream and juice from leaves (external use only).

    Then I researched a bit – and this article is simply an unpleasant scare crow. Please see the studies below as reference (there are many more).

    Main difference – wild comfrey (yellow flowers) contains higher amount of alkaloids than cultivated comfrey (violet/blue flowers). Secondly, the ROOT contains more alkaloids than leaves. And the leaves of the cultivated comfrey may not have any detectable alkaloids present.

    THEN – absorption rate of pyrrolizidine alkaloid lycopsamine in symphytum officinale through skin is POOR

    Simply – don’t use comfrey internally unless it’s an emergency. It is safe to use externally.

    And please amend this article. People die of eating too much salt and that is sitting on your table. There is plenty of research on comfrey.

    1. Thank you Radim – this article is not balanced and is fear mongering. Advising people to avoid all comfrey use has no basis in reality. External use of comfrey has a liver injury rate of ZERO.

    2. Hello I smoke comfrey I’m on my fourth year. My lungs are clearer from tobacco sold. It’s unclogged my pores in my lungs.
      I use the herb in cooking so much.
      My liver is fine, my body is fine. I can feel the Heath benefits from my use of dried comfrey leaves.
      Unfortunately I’ve been on spirt alcohol for 30 years with a major cut back.🎉
      I had my liver function tested and it’s working as it should for a 45 yo small frame female.

      My belief is because it’s oh so much more healthy than tobacco with oh so many chemicals that are proven to be toxic and are a bigger carcinogen than a herb with no chemicals added.
      More money for the governments and more cancers suffers from legal tobacco!
      It’s proven to causes more deaths than heroine, amphetamines, cocaine, LSD ect ect

      1. In my opinion, anyone that advises not to use comfrey is a government shill.

        Whatever they advise, I will do the opposite.

  3. I have used comfrey root extensively in my herbal practice for the last 25 years to quickly and effectively repair wounds, heal strains, sprains and broken bones (its been called “knit bone” for centuries) and in all my cosmetic products for the skin due to its ability to generate new cells.
    I have healed my own broken elbow for which the medical system offered nothing but “go home and suck it up”. I poulticed with comfrey root and the pain eased in 20 minutes after 6 hours of agony. In 2 weeks, there was no broken elbow. I heal my clients broken collarbones, shoulders (including strains and sprains), elbows and knees. I use it to treat carpal tunnel and sprains of wrist, hand, ankles etc. It is one of the most effective remedies in my herbal repertoire for these purposes. I have friends who use comfrey root externally extensively for their horses. I also use it in face creams and healing ointments for skin and lips.

    1. Have you ever used comfrey while pregnant? I used it for 2 days (about 30 mins per day). Just 1-2 leaves massaged with coconut oil and wrapped on my forearm. I used it then found out I was pregnant a day later. I’m only 4 weeks pregnant and I’m a freaking out so bad bc I saw the FDA says it COULD cause birth defects. I know the FDA isn’t the greatest at telling the truth, but I can’t help but worry. Please tell me that you know someone that used it in early pregnancy without it causing birth defects. Or that I used such a small amount that it wouldn’t hurt my baby!

        1. I agree, This was only short term external use. i have had wonderful success healing very nasty gaping wounds on horses legs. bathing with comfrey tea twice per day but having seen a horse fed comfrey, foaming at the mouth, sweating, heart racing, prancing around behaving like it was fed amphetamines for hours i would never allow any mammal free access to graze comfrey.
          I have also known people to start feeding their milking goats and milking cow regularly with it only to have them start coming down with all manner of mystery ailments and symptoms for months till finally dying. In hindsight their illnesses could be put down to the slow accumulative poisoning of their livers. Hepatoxemia is a real and true danger of consuming comfrey.
          Whether it is from the alkaloids or other (possibly seasonal changes in levels? ) components present in the powerful herb, It is DEFINITELY not worth the risk of killing your livestock. So PLEASE nil by mouth for EVERYONE.

      1. I would contact Doctor Jones, homegrown herbalist. He is a veterinarian as well as naturopath who has been practicing for 30 years on both and extremely knowledgeable on Comfrey.

    2. I appreciate your information here, as well as evidence of healing properties you have personally experienced. I am making and using my own comfrey poultices (from root powder/water) for lingering pain from bone marrow edema, as well as to treat my tendinitis in achilles. I have had impressive success, however I am not all healed. I am concerned I am overusing it (been using overnight for 3 weeks.). If I may, ask more about your poultice that helped your broken elbow? Was it root and or leaves, and how long did you leave on for each day?
      Thanks so much for your time

    3. PS. My comment was addressed to Robin Round.
      Also my poultice recipe is comfrey root powder with hot water, applied while moist and warm.

  4. Thank you Beryl for your article. Comfrey is an amazing plant, but I agree that it isn’t without serious toxicity risks. Herbalist here in France where I live are well aware of the pyrrolizidine alkaloids toxicity dangers, but mostly mention the dangers of consuming it.
    I have beautiful comfrey plants in my garden and I use them for making soil fertilizer. I “sometimes” make a balm from a portion of a root for my rare eczema manifestations and it’s amazing at how fast it heals, but because I know about its toxicity it is very rare that I do this. I know what causes the eczema and focus my efforts on avoiding the foods that trigger.
    I was just thinking of making a balm for my kitty who has a wound that she keeps scratching and opening. It gets to healing point and then she scratches the scab off. I thought maybe it could help, but I always check several sources before using anything on her or other wild animals that I care for. I’m glad I found your article first, it confirmed an intuitive sense, that it was a very bad idea.

    1. Many herbs are toxic in large doses. This is common knowledge. Not. secret or anything new. This is only one example. It is just nature. Poke Root can be toxic in large doses as well yet the history of its use and the success of it are all testimonials that the fear is grossly exaggerated. Small doses are unlikely to cause any issues in the overwhelming majority of people; even when taken internally. I find the issue is the modern obsession with large doses. It is a problem with many things. And choosing to call out one isolated chemical in a group of hundreds of them and then call it a boogyman is meaningless. Plant foods people eat every day contains chemicals that are known to cause cancer and all sorts of stuff when ingested in large amounts but no one is freaking out over that. Oxalates are a downright poison. But people eat oxalate foods and call it a super food. Everything is relative. They tried to do this with Sarsaparilla for years and every time the lie is scientifically debunked, people keep attacking it. The saying the dose makes the poison applies to almost all of natural medicine. People swallow Tylenol and Advil and all sorts of OTC poisons every day without blinking but will freak out over Comfrey. OR take a RX thinking it is somehow a safe drug because a doctor/big Pharma drug pusher; tells them it is safe despite countless studies showing otherwise. It actually makes me laugh how lost people are. It is just tragically funny at this point. It is the only way I can stay sane.

  5. Pretty interesting to read the author’s responses to commenters sharing their positive experiences using Comfrey. I read things like, “Oh, that is interesting” and “I didn’t know that” and yet the author remains absolutely, positively steadfast in her misinformed position that all of us (who apparently know at least a little bit more than her on the subject through personal experience and alternate information sources) should DEFINITELY NOT USE COMFREY in any quantity or for any duration to treat any ailment. If that doesn’t raise red flags for others then they can’t think for themselves and frankly – can’t be helped.

    We saw the same thing with Ivermectin – demonized by big pharma who didn’t want the public to know that billions of doses have been administered to humans over the course of several decades with fewer side effects than aspirin. True and widespread knowledge of the healing and PREVENTATIVE properties of that inexpensive and naturally derived drug would have absolutely interfered with the unlawful distribution of big pharma’s killer fake ‘vaccine’ product and very likely aided in the destruction of the entire pharma industry. Now the people whose immune systems got wrecked from the first injections are gonna line up for the Monkey Pox toxins being marketed as a cure when all the while the outbreaks of severe Shingles they are seeing on their bodies are the result of their own stupidity in destroying their immune systems with the first rounds of poisons.

    Worse, people exactly like this author – people, including doctors who have been erroneously elevated in our society to a status of expert when their only real accomplishment is to have completed a multi year indoctrination program that others were intelligent enough to bypass in our own learning – people who simply don’t know about the topics they are advising on and who have placed trust in the wrong sources help perpetuate lies and falsehoods that prevent people who are suffering or whose animals are suffering from making use of the free treatments available in their own back gardens.

    My 87 year old grandfather had been increasingly suffering from back pain that I had thought was due to bone spurs but that I learned later was actually from other complications. The comfrey cream I gave him to apply to the hurting area is THE FIRST THING anyone has ever shared with him that his given him noticeable and even incredible relief. He was blown away by the results and is very disappointed that after years of nearly unbearable pain and difficulty with mobility there was a cheap and accessible solution that no one ever offered to him.

    What we should be doing instead of demonizing effective natural remedies is educating ourselves on how to administer them to ourselves and our loved ones including our pets safely. We should also be questioning why it is that our brains don’t question injecting ourselves with steroids, for example, whose chemical compounds none of us likely know very much about at all, but that we feel great concern about consuming something like Comfrey which doesn’t just mask pain the way most big pharma drugs do but that also aids in the natural healing process of the body. It is well past time people took ownership of their health and stopped relying on the authority of anyone who is in the businesses of profiting greatly from perpetual illness. Here is a great video that sites sources for using Comfrey in all types of healing applications.

    1. No, they’re trying to stop people from poisoning their pets or themselves on accident. They provide solid evidence through the accumulated information in several peer reviewed articles. The link you provided cites two authors who don’t use science. I’ll take science any day, thanks for the information Beryl!

  6. Hi my name is malissa and I would like to know how comfrey to give my dog she had a ACL/ CCL going out is what the vet said and needs replaced! I wold love to know what I can do to heal her leg natural please !

  7. I fed my rabbits, ducks, chickens and goats comfrey for almost 20 years as a supplemental food. I never lost an animal in those years other than varmints’ killing them or old age and snakes. . I had the healthiest ducks, chickens, and goats you could have.

  8. There’s an article from noted herbalist Susun Weed where she basically refutes all your arguments. She had three separate samples of comfrey from the west coast, east coast, and Rocky Mountains sent to labs and tested for the aforementioned alkaloids. There were none. Other herbalists have also pointed out that the amount of comfrey administered to the lab rats in the study you mentioned exceed the amount most people would consume by an unrealistic factor.

    Most tellingly, Ms. Weed points out the kind of comfrey grown in the U.S. is descended from a hybrid created by an Englishman during WWII specifically to make it safe for consumption since there were food shortages across the U.K.

    Here’s the source article:

  9. Beryl,

    You should read into GCMaf, liposomal vitamin C, and do equal homework on comfrey. Don’t believe everything you’re told. Grow some comfrey yourself send it into a lab pay them to do gas chromatography. I’m sick of reading about the vilification of real solutions that actually work in curing autism, cancer, immune disorders etc and the morale doctors attempting to give to all of society these gifts and then having their lives completely destroyed, imprisoned, sometimes murdered, to stop the spread of sound medicine in its tracks.

    Why are there no medical texts from the Romans talking about poisoning resulting from Comfrey? For some reason the roman army did not think that comfrey had poisonous biocumlative properties but yet this society has decided within the last 25 years that it does have biocumulative properties and produces so called evidence which counters over 2000 years of opposing evidence… You would think there would be some evidence after administering to thousands and thousands of wounded soldiers.

    Have you ever had a family member dying and told by all the doctors trying to treat their cancer that they were screwed while doping them up on nerve gas repurposed as chemo drugs? My father survived doctors that shouldn’t be allowed to practice and colon and liver cancer after firing every single one. In the end he had to order mistle toe therapy from Germany which still to this day is not available from United States companies. We got it through a black market in New Orleans – illegally – to save my father. By the way if you live in Australia the only way you can secure Comfrey through purchase is on the black market. But we are all so sure the Australian government is protecting us. They know whats best for society as they always have.

    This is relevant in so many ways – such as pathogenic priming and gene therapy products advertised as “vaccines” which should be illegal and perpetrators should be tried at the hague for crimes against humanity from the doctors down to the nurses. Too many hold hands – hand in hand – with government narrative supporting major pharmaceutical companies that these things are bad and therefore we will do anything within our power to prevent you from having access. When it is that stifling action that is actually perverse and disrupts the progression of the evolution of our society – to find and secure the answers to good medicine.

    Do something constructive for our right to participate in the free market instead of spreading talking points with no proof except referenced information which has already been debunked. And i’m not talking Snopes and other fact checkers whos mere inception were created to further destroy the spread the gospel of sound medicine and other true information. Propaganda is meant to confuse and destroy our ability to discover truths in this world.

    God forbid mankind finds all the medical solutions within nature that were always there when government and pharmaceutical synthetics are the gospel for the cure.

    1. What you’ve said about purchasing comfrey in Australia is totally untrue.

      You can purchase the seeds easily, and the plant starts are available online.

      I have bought comfrey leaf from both The Herbal Connection and Austral Herbs. It says “not for ingestion” on the packet but that’s not stopping anyone haha.

  10. My horse takes comfrey when offered, I would never administer it. The point is , animals self medicate and know better than us what they need. The scare mongery around Comfrey could stop it doing good, like other things , some will have an adverse reaction, but that shouldn’t stop it being used full stop.

  11. It’s my understanding that even when I buy comfrey leaf to use in my weekly rotation of herbs, that labeling it symphytum officianale is a precaution taken by many bulk herb suppliers to err on the side of caution. What is most often labeled as symphytum officianale is actually symphytum uplandica. They are distinctly different looking in size and flower color, so identifying what’s growing on your pastures shouldn’t be difficult if it ever gets the chance to flower. Wild comfrey (symphytum officianale) is a smaller plant with yellow flowers, produces seeds, and should not be eaten. The hybridized comfrey that is big, tall and has blue or purple flowers was cultivated specifically to be eaten as a green at the dinner table by the entire family with the alkaloids being bred out of the leaf almost, if not entirely. It will not produce seeds. I would never ingest comfrey root of any kind, considering the high amounts of poison in it. I have never had a negative reaction to the use of comfrey leaf and have been drinking the strong standard brew/infusion for years and using it as a soothing, healing sitz bath after childbirth and trauma to that region. There is a reason country lore calls this lady “knit-bone” with its bounty of minerals and vitamins that aid so beautifully in healing and restoration of connective tissues.

    1. Oh now I get. Thanks for the clarification. The comfrey growing everywhere here in Nigeria has yellow flowers. So I was surprised when I came online and saw purple flowers.

      Now my question, Leale, is: which of these variations do you recommend/which do you use to treat said trauma?

  12. It’s hard to find because people have been scared away from it. I got a lovely comfrey starter at a seed plant exchange in Taos. I use it for my chickens, horses and dogs. I make a crushed compound with coconut oil and use topically.

    While I understand that it does have the potential to be toxic, for rats. I have not seen any negative responses from my animals. They look for it.

    I’d also would like to see studies that were done in the last ten years and on equine response in particular. Not just rats.

  13. It is just an opinion. I had surgery on my broken ulna 10 days ago, took Symphytum30 3 x5 and my surgeon said I am ahead in my recovery 🙂
    Also, my vet says no raw feeding and no garlic. I do BOTH. My dogs, ASD, live longer than average and do not have fleas

    1. Lana, the Symphytum you speak of is a homeopathic remedy. There wont be a problem with that at all – it is very diluted. And, as far as I’m concerned, well done with both the raw feeding and the garlic. 🙂

  14. I don’t know, my Whippets have grazed on Comfrey from the garden for as many years as I have had them (18yrs). They will actively seek it at certain times. Another Whippet breeder friend always has a large patch in her vegetable garden and will open the gate for her Whippets to graze – they dive in and enjoy with gusto! She has been breeding and showing Whippets for probably 40-50 years and I am pretty sure that liver problems has not been something she has experienced.

    1. Hi Noela. What I am saying in this article is that there are dangerous chemicals in Comfrey. Its a bit like smoking – some people can smoke their entire lives and not get cancer. Others can get it from smoking once. But, I do stand by what I say. If we know it contains dangerous molecules, we can and should avoid it. (Smoking and comfrey ;-))

  15. Certainly always advise caution useing comfrey, but I personally found that at a time I was severely anaemic taking the tea daily for six weeks helped me heal very fast after a tooth extraction.
    The liver can actually regenerate to an amazing degree. Please watch this film and consider if Juliette de Baraclai Levi’s award winning hounds look as if it did them harm?

    1. Hi Fritz. Some people smoke everyday and live to 100. But smoking exposes your body to a carcinogen, which might or might not cause cancer. Comfrey is the same sort of situation. I would rather err on the side of caution and not smoke and not eat or feed Comfrey.

  16. I used to grow Comfrey in my garden in Zimbabwe for my dogs with no problems, since being here have not found the plant – interesting.

  17. I have never been able to grow comfrey simply because my dogs eat it down to ground level. I cover it, fence it, try to prevent it, but still they break it down to get to the plant. Surely they aren’t purposefully poisoning themselves? I know that dogs self-medicate with various plants in the garden – Tecomaria capensis for example or Zinnias – so surely there must be some medicinal benefit otherwise they would avoid it?

    1. Julia, they do self medicate. And yes, there are plenty of benefits of Comfrey. So, either they know something we don’t (perfectly possible) or maybe it just tastes nice. 😉 Either way, if I were you, I wouldn’t plant it….

  18. Juliette De Bairacli Levy talks about and has used comfrey extensively (in her book – The Complete Herbal Book for the Dog) – I know that she has since passed and this book was first published in 1955 and reprinted in 1978 but could she have been that wrong?? I have bought from a product (Seaweed Mineral Food) that is her original formulation. It does declare on the ingredient list Comfrey Herb Powder (amongst other things) but does not declare the amount. I was about to buy some more, do you really think its dangerous for my beardies? They get 1/8t in their goats milk every day??

    Please let me know what you think

    1. Sue, I really truly hate dissing other people’s products. But yes, to be absolutely safe, I would say don’t feed that product to your dogs. Even a small amount can be dangerous. Perhaps ask them if they have anything similar but without the comfrey.

      And yes, Juliette De Bairacli Levy was mentioned in the one article that I read about this today. Even today, a lot of people still recommend comfrey. And I have used it in the past on my own horses. But this is my now considered opinion.

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