Comfrey - The Facts

August 13, 2004

Comfrey (Symphytum officinale or Symphytum x uplandicum), has a long history of medicinal use. Yet Comfrey is a herb surrounded by controversy. To some it is virtually a panacea, to others it is a dangerous and poisonous weed. The world of herbalism abounds with anecdotal accounts of its virtues, but there have been few serious studies of ts medicinal use. What has instead appeared in the scientific literature are studies which claim to emonstrate harmful effects and this has led to the use of Comfrey being restricted by its classification as a poison. Australia was the first country to do this but others have followed. The reason is that Comfrey contains pyrrolizidine alkaloids these are toxic substances.

The pyrrxolizidine alkaloids (PAÂs) found in Comfrey are not responsible for its therapeutic effects. Alkaloids are plant substances which contain nitrogen, and can have high phamacological activities  morphine, quinine and nicotine are examples. Comfrey leaves contain about 0.06% alkaloids, and roots about 0.2 to 0.4%. Pyrrolizidine alkaloids contain two fused five-membered rings with a nitrogen atom common to both rings. They form a highly diverse group of chemicals and are widespread in the plant kingdom. Some, but not all, are quite toxic, particularly to the liver. There are many well-documented cases of livestock poisonings. Human poisoning occurs largely in the third world from contaminated food or herbal teas and a liver disorder known as veno-occlusive disease often follows.

A number of important issues are embodied in the Comfrey dilemma, issues which have much broader implications for herbal medicine. Should a medicinal plant which has a long history of safe use be regarded as dangerous because it contains low levels of toxic chemicals? Should a medicinal plant be regarded as carcinogenic because it produces a few malignant tumours in inbred, susceptible laboratory animals when fed to them at unrealistically high levels over a whole lifetime? To address these issues requires rationality and good science, but above all common sense. So far these have been lacking from the Comfrey debate. It has been a debate argued from extremes.

On the one hand a group of well-meaning scientists actively lobbied the Australian government to have Comfrey restricted. The basis for their concern was just two toxicological studies, both of which have doubtful relevance to normal human use. The arguments generally used were related to pyrrolizidine alkaloids, not Comfrey itself, and their theme was that pyrrolizidine alkaloids should be entirely eliminated from human diet and human medicine.

Their zeal saw Comfrey in some states of Australia receive a higher poisons classification than arsenic, hemlock,belladonna and strychnine. In Victoria Comfrey

was restricted from external use when there is no evidence

that this is harmful. The hysteria generated by their crusade saw a coroner file a report in Australia attributing a human death to just a few meals containing

Comfrey leaves.

On the other hand the defence for Comfrey has been at times emotional and irrational. It is not enough for herbalists and naturopaths to say, "I have used it and

never seen any harm," or for a consumer to say, ÂIÂve taken

50g every day for 10 years and IÂm normal."Valid as these

observations may be, similar arguments have been used

to defend, for example, cigarette smoking. It does not

impress the scientific community to argue emotionally

or from personal experience.What does impress are new,

objective facts, or a critical interpretation of the existing facts.

So what are the facts? The relevant issues can be embodied in the form of six questions. By dealing with these questions, the facts can emerge. How do the toxicological studies on Comfrey compare with those for commonly used plant substances?

The first study by Culvenor and associates was concerned

with the acute and sub-acute toxicity of the PAÂs

extracted from Russian Comfrey (Symphytum x uplandicum) leaves.4 These PAÂ s were administered by injection, so it is difficult to relate this to the oral use of the Comfrey leaf, but ignoring this we can still arrive at some pertinent facts.

We can convert the injected dose of alkaloids in rats

to the equivalent oral human dose of leaves based on the

fact that a leaf consistently contains 0.33mg of alkaloids

whether it is old (large) or young (small).5 These projections are given in Table 1. Clearly from this information, normal human consumption of a few leaves per day does not pose an immediate threat to health, a fact acknowledged by Culvenor.

The dose needed for death is impossibly high. How could anyone possibly consume 66,300 Comfrey leaves at one sitting  more than the personÂs body weight in Comfrey? How could one even consume this amount over 10 days? Yet a coroner has reported, on the basis of medical opinion, that someone died of acute Comfrey poisoning.6 This is a travesty of common sense. Clearly it is impossible to die from acute Comfrey toxicity. Other factors must have been at play.7

Even to show some mild impairment of liver function one would need to consume 4.5kg of leaves per day for 3 weeks (assuming 5g per leaf). Yet there are 2 medical papers associating, by hearsay only, acute PA toxicity in the form of veno-occlusive disease with Comfrey medications.8,9 In neither case was it verified scientifically that herbal preparations used by the subjects contained Comfrey. Also it was not ascertained

that this was their only source of PA intake. This is a

travesty of scientific method and a poor reflection on the

journals which accepted these articles for publication.

Doubly so, because once something is in print in a journal it is often quoted in a superficial way as fact, with no analysis of the validity of the original information (as is the case in some internet forums).

Is Comfrey carcinogenic?

Here we refer to the second toxicological study on Comfrey by Japanese workers entitled, "Carcinogenic Activity of Symphytum officinale".10 A foregone conclusion, isnÂt it? The title says it all. But is it a fact? Although this is a relatively recent study, it does not satisfy many of How carcinogenic are pyrrolizidine alkaloids? The question of the carcinogenicity of PAÂs is a controversial area. In laboratory animals only a handful of the large number of PAÂs have been studied and while malignant tumours have been induced in many organs, usually it has only been in a small percentage of the test population. Most studies have reported the induction of liver tumours, but there is controversy as to whether these are malignant. Chronic PA poisoning gives rise to liver nodules, and the tumours found in these are probably benign not malignant.1 One scientist in the field concluded, "As far as pyrrolizidine alkaloid carcinogenesis is concerned then, an important part of the argument rests on the disputed identity of the lesions reported as hepatoma".1 The study of PA toxicity is not a crowded field, so there has not been exhaustive examination of carcinogenicity  often preliminary studies are not followed up. This can result in things being taken for proven facts which are far from properly studied. No-one, for example, has repeated the original arcinogenicity study on Comfrey, despite all the controversy. Given the controversy over the carcinogenicity of PAÂs as observed in the laboratory, it is noteworthy that there has never been a link with PA intake and cancer in human or in veterinary studies, despite the many recorded cases of livestock poisoning.1 PA poisoning (venoocclusive disease), is high in JamaicaÂdue to indigenous herbal teas  yet the incidence of primary liver cancer is lower than in western countries. Also primary liver cancer is not more common in people with livers damaged by PAÂs than in people with cirrhotic livers due to alcoholism.2

Is it valid to generalise about PAÂs in terms of

their toxicity and carcinogenicity?

In one study rats were fed green leaves of Senecio jacobea

(Oxford Ragwort) and Comfrey in their diet.3 At 5% Comfrey leaves there was no sign of toxicity, but at 1% Ragwort leaves in the diet there were many signs of toxicity, including changes in liver enzyme activity.3 Even 20% Comfrey leaf in the diet did not cause the liver enzyme changes from 1% Ragwort.3 Comfrey PAÂs are therefore much less toxic to the liver than those of Ragwort. This would explain why Ragwort causes livestock poisoning whereas Comfrey is used as a livestock feed, with excellent results. In fact there are no recorded cases of livestock poisoning due to Comfrey.

What do the toxicological studies on Comfrey

really show?

Despite all the rhetoric there are in fact only two full-scale toxicological studies on Comfrey. To quote other publications which merely interpret the findings of these two studies does not constitute additional evidence. 2 Professional Review

Alkaloid Dose Effect Equivalent Human

for Rat Dose of Leaves

284mg/kg Deaths 66,300 Jeaves

71 mg/kg No effect 16,600 leaves

8.9mg/kg Reduced liver 890 leaves/day

(9 doses over 3 weeks) function

Toxicity Studies of Symphytum x uplandicum Leaf alkaloids.4 the criteria demanded for a rigorous assessment of carcinogenicity. Rats were fed Comfrey leaf from 8 to 33% of their diet, thus all test levels exceeded the 5% maximum recommended by the EC. Test levels for the

root were 0.5 to 4%. Liver tumours were observed in all

test groups, but the vast majority were probably benign tumours (hepatomas), indicating hepatotoxicity at the

levels tested. For the rats fed 8% Comfrey leaf only one

benign tumour occurred late in the study, indicating low

toxicity and absence of carcinogenicity. Only 3 definite

liver cancers (haemangioendothelial sarcomas) occurred

randomly throughout the 7 test groups, a level which has

neither statistical nor biological significance.

In order to prove biological significance for a carcinogen

the following criteria must be demonstrated:11

A dose-response relationship

A decreased latency period for the tumours

A more anaplastic tumour type than controls

Early or pre-neoplastic lesions

Capability to produce a reliable and consistent

increase in tumour incidence

None of these criteria was satisfied for the liver

sarcomas. The fact that rats could be fed 33% Comfrey

leaves in their diet and still survive to old age is testimony to its relatively low toxicity.How many drugs could survive such scrutiny?

Let us take everyday tea as an example. Tea is the dried fermented leaves of Thea sinensis, a herb indigenous to the Indian sub-continent. Tea contains caffeine and tannins, including tannic acid, as its main constituents.(12) A superficial examination of the literature reveals the following: Caffeine is a known teratogen,(13) a suspected carcinogen,(14) and in animal feeding studies causes severe weight loss and thymic and testicular atrophy.15 Tannins have demonstrated carcinogenic effects, they inhibit digestive enzymes, inhibit mineral absorption and are highly toxic to the liver and kidneys.16 Human deaths have resulted

from the administration of tannic acid.17 The carcinogenic

activity18 and toxicity19 of the tannins from tea have

been demonstrated in animal experiments. In human

studies tea can cause thiamine deficiency,20 constipation21

and epidemiological studies have linked black tea with

rectal22 and oesophageal cancers.18 Of course, common

sense tells us normal use of tea is safe, but the scientific information taken out of context is quite damning, in fact more alarming than that for Comfrey.

It is worthwhile to examine why this considerable

scientific evidence for the toxic nature of tea has not made headlines and has not resulted in tea being restricted or entirely banned in the public interest. Just as a series of promising pharmacological studies does not imply the birth of a new wonder drug, the findings of toxicological studies can be of only minor relevance to the common experience. Differences such as species studied, dose, form a dose, interaction with nutrients, and duration of dose all combine to explain why the results for tea and its components should have little bearing on the moderate consumption of the beverage. Qualified herbalists can therefore be forgiven for taking a similar stance about Comfrey. The main difference is that toxicologists and legislators are familiar with tea, but to them Comfrey is alien and unnecessary so they are prepared to believe the worst.

Assuming Comfrey was a proven carcinogen,

what is the relative risk of drinking Comfrey tea?

Life is carcinogenic  so it has been said. Here we are

undertaking an assessment of relative risk. Dr Bruce

Ames, a respected scientist in the fields of carcinogenicity and mutagenicity has published an article in the journal Science entitled "Ranking Possible Carcinogenic Hazards".23 The review discusses reasons why animal cancer tests cannot be conclusively used to predict human risks but such tests may be used to indicate that some chemicals might be of greater concern than others. An

index was developed called HERP Â Human exposure dose/Rodent potency dose. In this study it was found that inhaling air in the home absopbs 598mcg of Formaldahyde, and that cooking bacon causes the inhalation of .4 mcgs of nitrosamines which puts the 750mcgs of PA's you'd ingest from a cup of comfrey tea in perspective.

So now we have the facts:

1. There is some doubt that pyrrolizidine alkaloids

cause cancer outside of laboratory experiments.

2. The pyrrolizidine alkaloids in Comfrey are qualitatively

and quantitatively less toxic than pyrrolizidine

alkaloids found in known poisonous plants, e.g.


3. Atoxicological study has shown that normal human

use of Comfrey cannot cause death or toxicity.

4. The incidence of malignant tumours induced by

long-term experimental feeding of high levels ofComfrey to rats is neither statistically nor biologically


5. Toxicological studies of tea are far more extensive

and alarming than those on Comfrey, yet tea is widely

used without apparent harm or restriction to its use.

6. Even assuming that Comfrey was carcinogenic, the

relative risk from its normal use is insignificant when

compared to normal exposure to other carcinogens.

A recent study of long-term Comfrey users tends to

confirm the premise that normal use of Comfrey is not

hepatotoxic.24 Biochemical tests revealed no evidence of

liver damage in 29 users, even for those who had been

regularly taking up to 25g/day for more than 20 years.24

Comfrey was never regarded as a poisonous plant.

Despite the findings of two laboratory studies, it should

maintain this status. However, in the interests of the public and the herbal profession, a rigorous study of its longterm toxicity should be undertaken. Otherwise the

Comfrey issue will continue to damage the credibility of

herbal medicine in many countries.



1. McLean, E.A: Pharmacol Rev 22, 429 (1970); 2. Bras, G. et al: J Patho Bacteriol

82, 503 (1961); 3. Garrett, B.J. et al: Toxicol Lett 10, 183 (1982); 4. Culvenor, C. C.

J et al: Experientia 36, 377 (1980); 5. Mattocks, A.R: Lancet 2, 1136 (1980); 6. NZ

Dept of Justice, CoronerÂs report on the death of Paul Edward Neutz, March 12,

1986; 7. Beckham, N: Wellbeing, April (1988); 8. Weston, C.F.M. et al: BMJ 295,

183; 9. Ridker, P.M. et al: Gastroenterology 88, 1050 (1985); 10. Hirono, I. et al:

JNCI 61, 865 (1978) 11. Borzelleca, J.F. et al: Fd Chem Toxic 23, 551 (1985); 12,

Trease, G.E. and Evans,W.C: Pharmacognosy, 12th ed., Balliere Tindall, London, P

622 (1983); 13. Collins, T.F.X. et al: Fd Chem Toxic 25, 647 (1987); 14. Rozenkranz,

H.S. and Ennerver, F.K: ibid 25, 247 (1987); 15. Gans, J.H: ibid 22, 365 (1984); 16.

Deshpande, S.S. et al: Adv in Exptal Med and Biol 177, 457 (1984); 17. Kreanoski,

J.Z: Radiology 87, 655 (1966); 18. Morton, J.F: Science 204, 909 (1979); 19. Panda,

N.C. et al: Ind J Nutr and Diet, p97 (1981 ); 20. Ruenwongsa, P. and Patannavibag,

S: Experientia 38, 787 (1982); 21. Hojyaard, L. et al: BMJ 282, 864 (1981); 22.

Heilbrun, L. K. et al: Br J Cancer 54, 677 (1986); 23. Ames, B.N. et al: Science 236,

271 (1987); 24. Anderson, P.C. and McLean, A.E.M.: Human Toxicology 8 (1)

55 (1989).

Comments (52)

  • johnyb

    Hi Moonwolf,

    I grow fresh comfrey at home for personal use, but i do not prescribe it in clinic. Comfrey is also a great compost activator for the garden, so, like so many herbs, I utilize it's wonderful synergisitc qualities.

    I have used comfrey topically only upon myself and immediate family for wound healing, broken bones and cartilage tears and strains. I have found it very effective at reducing healing times and reducing scarring.

    As I do not see many of these ailments in clinic i do not make a comfrey a part of my dispensary, but do have available herbs such as boneset, calendula, etc.

    For me, I'd be more worried about my weekly CO2 intake from a drive downtown, than any poisoning from a comfrey poultice.

    Now, to Eric. The weight of time and use does act in favour of many herbs, as does too the fact that huge amounts of herbs are being sold round the world unregulated in health food stores and the like. How more people have not died amazes me, but is testament to the safety of herbs. If drugs were freely available willy nilly for a month for self administration we would have deaths and seriuos interactions limited only by the imagination.

    I am more concerned about liver damage in society from alcohol, hepatitis, legal and illegal DRUG use than i am about the topical use of comfrey. I've put my thoughts in the above post.

    I'm a fast typer when i get going. Ever used herbs in practice Eric(not comfrey of course)?

  • rusty_blackhaw

    Of course, John. I have used and still use a number of herbal drugs.

    If you have any responses to points I raised, instead of continually trying to create distractions with personal remarks, such responses would be appreciated.

  • johnyb

    I'm finished on Comfrey for this week, I put a weeks post into one LOL.

    My question regards your use of herbs is not a personal distraction, far from it, just a lead on thought as i typed away. The reason i asked is to ascertain whether you only use herbs for personal use, and/or have a select dispensary you use in clinical practice as a "physician" ( a term that has been misused by alt medicine practitioners in the past here in Australia, so i am presuming you are a doctor of medicine.

    "Herbal drugs". Is this a term you apply to the herbs themselves, or does this mean you use/prescribe only extracted actives of herbs, ie not the whole herb. Maybe you use both? Do you entertain the possibility that herbs may exert their therapeutic effects (I won't say "powers"!)via the synergistic activity of many actions (there are exceptions)that may reduce side effects etc, or are you simply interested in a single active applied to a disease state, and would therefore prefer to use an isolated active from a herb and disregard the balance.

    My curiostiy is driven by interaction with local doctors who do use herbal medicine to varying degrees, and seem to have divided opinions on this. Science is divided also. Just curious as to where you sit,


  • rusty_blackhaw

    Any further personal comments about my philosophies, hobbies etc. or inquiries along these lines should be directed to e-mail.

    As you say you're through discussing comfrey for now, that'll wrap up my exchanges with you in this thread.

  • johnyb

    Might be time for a hug Eric?

  • kfgesq

    Too bad Johnyb that was an interesting quesion. why wouldn't someone want to respond? I think that the natural subsance is most likely the best from what I understand. I haven't done any extensive research on it but it seems like common sense that a plant with healing properties has more than one attribute and that because it does,it doesn't make sense that isolating th main ingredient is the best course. It would seem that it should be taken in it's natural state and that the natural state of the plant has the other ingredients for a reason. I think that is why isolating the main healing ingredient in drugs makes for a poor substitute and that is probably why there are so any side effects when done this way. I hope this makes sense. Too bad Eric won't comment. Maybe this is an area where he can't simply bash your theory.

  • rusty_blackhaw

    No, it's that this flawed concept deserves its own separate discussion, not to be thrown in as a distraction when arguments for consuming comfrey bog down.

    It's an appealing idea - that Mother Nature/God/the Earth Spirit created herbs for human healing. According to this philosophy, it's wrong to try to isolate a medically useful compound or compounds from an herb (and leave the useless or dangerous ones behind), but that everything in the whole herb magically, syngergistically and safely works together and must be taken as a package.

    The easiest way to refute this is to ask believers if they take deadly nightshade (Atropa belladonna), digitalis leaves, castor beans (instead of castor oil), toxic mushrooms or any other highly poisonous plants in the "whole herb" form. Thousands of plants contain toxic substances, yet some are highly useful when the toxins can be eliminated or reduced to safe, predictable levels, creating good drugs.

    Heart failure patients are much better off taking digoxin in prescribed doses than they would be consuming digitalis leaves, in which case they'd be getting fluctuating amounts of the drug, varying between ineffective and highly toxic.

    Comfrey's problem goes beyond this, of course, since even if one was confident that suppliers could consistently remove all or most of the toxic alkaloids, there's still the problem of the lack of studies showing that it works.

  • johnyb

    Erick has given us as examples of herbs that are the exception rather than the rule when it comes to synergism of action. As I said, there are exceptions, many dangerous,and he duly noted those exceptions. For every exception there exists 100 examples of herbs that are not toxic or dangerous, and that work therapeutically using many different actions, with very few side effects, and an excellent safety profile, and have done so for 100's of years. Thats why herbalists only use a few hundred herbs of tens of thousands, because the others were found to be dangerous...the hard way!!
    So when Eric tries to refute this with his extreme examples, we don't see the whole picture.

    And according to the idea that within nature lies a cure for all disease, in that every living organism has both a positive and a negative influence on another, does not necesarily infere that it opposes synthesizing an active ingredient to help mankind. Rather it emphasises the principle that where possible, a natural product should be used in preference to a synthesized chemical. It does not mean opposing modern drugs to cure diseases that natural medicine has not yet been sucessfully applied to. The challenge of science should be to find the most natural remedy to cure the disease.

    It is interesting to note that pharmacologists also now recognize the principle of synergism of action, but when used, prefers to call them "buffering compounds"!

    I see the benefits of using both natural products and drugs when needed. And I think sick people would be better served if reductionist scientists and advocates of nature cure could reach a middle ground, learn from each other,stop fighting with each other, and put their energies into assisting humanity.


  • moonwolf23

    I'm not sure if its completely a case of scientist vs scientist. Though that may play a part in it. Malpractice insurance or the like in other countries may play a part in it as well. THe other thing would be how alternative practioners are viewed by regular dr's.

    more later.

  • johnyb


    I think a visit to an emergency care unit at a hospital is testament to the effective life saving medicine of syntheiszed drugs.

    I also think that talking with a PMT sufferer who nolonger suffers a week of pain and depression every month because of an effective herbal prescription and lifestyle changes is testament to the benefits of natural medicine.

    Where's the middle ground? i don't know, but it would be nice to find it.


  • rusty_blackhaw

    "The challenge of science should be to find the most natural remedy to cure the disease."

    Change "natural" to "effective and safe" and most everybody would agree - although this would not please those who on philosophical grounds reject anything "chemical" in favor of "natural" substances which must be intrinsically safer and purer.

    Except that in the case of herbs, we are dealing with a stew of complex chemicals, which can help us, hurt us or be inert.
    It's when we move away from magical thinking towards evidence-based reasoning that herbalism works best, and becomes a true part of complementary medicine. It can be a breath of fresh air and a source of valuable drugs for the future, or a superstition-laden relic of the past.

    Exercise, stress reduction measures, healthy diets etc. have long been urged by practitioners of mainstream medicine. It's interesting how certain alt med advocates now claim to have invented them. :)

    Still hoping for those answers about comfrey...

  • johnyb

    What answers are you looking afor about comfrey? You sound like I have been avoiding a question(s) of yours, when in fact I think you'd be hard pressed to find a more comprehensive post that that I initiated to start the post.

    "Exercise, stress reduction measures, healthy diets etc. have long been urged by practitioners of mainstream medicine. It's interesting how certain alt med advocates now claim to have invented them. :)"

    Exercise, eating natural food, drinking pure water, and using natural medicines were the tenets of the founders of modern medicine. Galen, Hippocrates etc. You know as well i do Eric that nutrition and preventative medicine are areas that modern medicine has largely neglected until lately. When was the last time anyone went to their doctor and was asked about tyheir diet?? C'mon, it rarely happens. I'm not sure that preventative diets, nutrition and exercise can be properly discussed with a doctor these days in under 7 minutes (maybe you'll get 10 in Australia if you're lucky), at least that's the feedback from patients that I receive.

    We differ in that you would like to see herbs examined, their actives isolated, and synthesized so as to make drugs. I on the other hand would like to see the whole herb used, and synthesization used only where needed. Eric thinks herbalism should be integrated into mainstream medicine and used only by doctors. I think herbalism should remain in the hands of herbalists and administered only when modern medicine has a common consensus on herbal medicine. I think we can do better than 7 minute consultations for sick people, and would hate to see herbs lost (by not being used) in such a system. Not all doctors share Eric's willingness to use herbs as part of practice, in fact many would refuse to use them.

    There are also an increasing number of doctors more flexible than Eric, who are, in increasing numbers, attending herbal conferences and colleges/Uni's with an open mind, and finding themselves better practitioners after applying principles of traditional herbal medicine.

    Still hoping to find a middle ground


  • rusty_blackhaw

    Points on comfrey that you haven't addressed include:

    The discovery of toxicities in traditional herbal remedies using modern investigational methods (i.e. the tragic case of aristolochia, the ancient Chinese "remedy").

    The multinational restrictions placed on comfrey after its hazards were discovered.

    The solid link between the specific type of damage that comfrey causes in liver tissue, and the appearance of clinical damage.

    The lack of evidence that comfrey works.

    The consensus among respected herbalists, a prominent herbal product trade group, cancer specialists and other doctors that internal use of comfrey is a bad idea.

    It's also puzzling that in the other discussion of comfrey (on broken bones) you dismissed the recommendations of an Australian naturopathic group regarding the supposed benefits of comfrey taken internally, as not being representative of the feelings of naturopaths in your country, and that you recommend not ingesting comfrey. Yet here you are in the opening of this thread, essentially saying that the concerns about comfrey toxicity are alarmist and that the stuff is safer than ordinary tea.

    Quite a mixed message there.

    And you have still not given us a single piece of evidence that comfrey use is safe in children.

    To move on to sensible nutrition and other preventative health measures: Of course these are a major part of mainstream medical practice. It's a message many people don't want to hear (i.e. the importance of losing weight and exercising), but it continues to be stressed. If you'd like to see a small part of the education being offered just in the realm of dietary fiber, check this site.

    "Eric thinks herbalism should be integrated into mainstream medicine and used only by doctors."

    This is another example of your making up an unflattering statement and attributing it to me. I suggested here (and have elsewhere) that herbalism complement mainstream medicine so that patients have an opportunity to choose from the best therapies available. If you can find a single statement by me in this forum that herbalism should only be practiced by doctors, quote it. Otherwise, please cease inventing false statements that you can conveniently shoot down.

    Unfortunately, there seems to be a fear among some herbal practitioners that if an herbal drug is shown to be safe and effective through good research and enters mainstream practice, that it won't be "alternative" anymore and they will somehow have "lost" something (influence? income potential?). But when an effective herbal drug enters general use and helps more people, the patients are the winners.

  • johnyb

    Now Eric, on aristolochia, we both know that the problems concerning this herb started when it was used outside of it's traditional TCM usages by less than university trained herbalists, and that in fact the wrong genus of herb was used.

    Using your tactics, there are many things in my post that you didn't address.

    In the 10 minutes I have, let me say AGAIN that comfrey is not to be used internally, and that respected herbal texts such as the Materia Medica of the Southern hemisphere and the British Herbal Pharmacopeioa do not contraindicate comfrey for external use. Eric and myself are both aware of the differences between clinical evidence, and scientific evidence. In the case of comfrey we herbalists rely on historical clinical evidence that has been gathered via use of the herb over time. This contrasts scientific evidence of use via analysis of actives, and rigorous testing.

    I would welcome further scientific testing on comfrey, and other herbs, but please stop continually giving me the "where's the scientific evidence" on every point, because you know that most herbs have not been rigorously tested yet, and that to analyse every herb would take 100's of scientists decades. You also know that most herbs that have been well tested pass the mark. You also know that the vast majority of herbs have been safely used for a long peroid of time by many people, and have excellent safety profiles.

    You also know that most drug drug interactions are found after medications are in general use, and that this same "where's the evidence" argument can be applied to them, to a degree.

    I am glad to hear that you think herbs should remain the medicine of herbalists. Further to your comment, I, along with ANTA in Australia are strongly advocating (and actively lobbying govt.) to lift minimum education levels of herbalists to a 4 year university health science degree. We are only one year off this standard at the moment. We recognize that if we are to be taken seriously (and not have people like yourself throwing strange websites up to us infering some association)then we must basically be trained as medical professionals. And it's working, our degree courses are excellent.

    The problem in the past is that it has been far too easy to do a 12 month course on herbs and enter the health feild as a "herbalist". How more people have not been killed both amazes me, and is testament to the safety profile of herbs.

    I don't have any problems personally if a herb is synthesized and used for a specific use that helps a patient, not at all, as long as the intended traditional or current use of the herb is not thrown out with the bathwater. But this rarely happens because common sense prevails.


  • rusty_blackhaw

    Your statement on aristolochia is incorrect. Cases of poisoning related to this traditional Chinese herb have occurred around the world, including the setting of herbalist therapy. More on the problem. And a detailed analysis from an alt med advocate who thinks the FDA did the right thing in protecting the public from aristolochia, which has appeared as an unlabeled ingredient in complex Chinese herbal mixtures.
    The point here, once again, is that despite an extensive history of use, the serious toxicity of an herb can go unnoticed in casual practice. The same thing occurred with comfrey, and is a reason to require evidence of safety based on adequate animal and human testing.

    It would certainly not take '100s of decades' to do studies on many of the products being churned out by the multibillion dollar supplement industry. It only takes the willingness to invest a small chunk of the industry's large profits toward ensuring human health and safety.

    "I am glad to hear that you think herbs should remain the medicine of herbalists.' No, you've misquoted me again. Here's what I said in my last post: "I suggested here (and have elsewhere) that herbalism complement mainstream medicine so that patients have an opportunity to choose from the best therapies available."

    Thanks for making a minimal attempt to address the unanswered questions on comfrey. Now, if you could speak to the remaining points:

    The multinational restrictions placed on comfrey after its hazards were discovered.

    The solid link between the specific type of damage that comfrey causes in liver tissue, and the appearance of clinical damage.

    The lack of evidence that comfrey works.

    The consensus among respected herbalists, a prominent herbal product trade group, cancer specialists and other doctors that internal use of comfrey is a bad idea.

    And you have still not given us a single piece of evidence that comfrey use is safe in children.

  • johnyb

    By now I think most people on the forum appreciate the difficulties entailed in discussing anything with Eric, and might understand my decicion to respectfully bow out of this conversation.

  • rusty_blackhaw

    I am sorry you don't wish to address those remaining questions, John.

    There is one thing you could clarify. You've hinted in this forum recently at an interest or practice in naturopathy. Particularly as you've been very insistent on knowing about my professional background, could you provide similar information about your own work, i.e. are you a naturopath?

    Thank you.

  • moonwolf23

    no not really. Granted i'm scrolling past the journal vs journal debate. Don't know enough and it frankly confused the heck outta me.

    Personally i was hoping a more indepth discussion on what good comfrey does and why it is better than say boneset.

    though i get it don't use it interanlly. and oh yeah please no techno talk.

    eric can you ummm please dumb down why you don't like comfrey if taken externally in a salve applied not directly to the wound?

    thank you.

  • rusty_blackhaw

    moonwolf23, I responded here because it was being argued that concerns about internal use of comfrey are unjustified.

    I don't have any strong feelings about external use of a non-root based comfrey product on intact skin, provided that it is not employed in pregnant or nursing mothers or in children.

    If people otherwise want to use a comfrey salve and don't mind the absence of scientific evidence that it works for the various conditions for which it's promoted, it's their time and money.

  • veeja11

    I think we all need to give Eric a hug

  • rusty_blackhaw

    I suggest that we give the snide comments a rest.

  • silversword

    ...and another interesting thread bites the dust...

  • rusty_blackhaw

    Zombie thread! Run for your lives!!!

  • eibren

    Eric, I could swear you recommended Aristolochia to me in another thread, and that I then said I would be more inclined to try Astralagus....


  • rusty_blackhaw

    You will find that I never recommended Aristolochia to anyone; on the contrary citing it as something to avoid due to serious renal toxicity. Since you bring up the subject, it's a good reminder that one should be very careful about imported herbal mixtures that don't list all the ingredients (or do so inaccurately) on the label.

  • eibren

    I wonder if comfrey would close up spider veins.


  • gringojay

    Butcher's Broom more useful for varicosities than comfrey.

  • eibren

    Sorry, it was Andrographis.

  • simplemary

    Really interesting debate. I've been growing & using comfrey for years & have found it to be relatively harmless & quite helpful. I've used it internally for torn tendons & broken bones & externally for everything from chemical burns to chapped lips. I don't disagree or agree with either side, however, since debates (& research) like these tend to be built on other debates (& research) with similarly unsuccessful & frustrating results. It is always useful to keep in mind that ANYONE can be sensitive to ANYTHING or likewise predisposed to a negative reaction/cancer/death if the right triggers are hit. Therefore, MHO is that herb use should be tailored to the individual & there is enough variety out there to choose from so that if YOU are uncomfortable with one thing (for yourself or another) then respect the feeling. And respect that others have different experiences that lead them to different conclusions. Comfrey, to me, is the herb kingdom's silver (dandelion's it's gold). I will use it with confidence with the respect that the plant itself also demands.

  • rusty_blackhaw

    There are people who've smoked three packs of cigarettes a day for their entire adult lives and never got lung cancer. Ditto people who drink heavily for many years and avoid cirrhosis of the liver and all the complications that go with it.

    Anecdotes don't however reassure us that such practices are safe, merely that some people can get away with risky behavior. For comfrey, the dubious benefits of internal use arguably don't outweigh the risks of serious liver damage.

  • simplemary

    It's odd how "anecdote" --the stories of the actual uses of the herbs over, oh, thousands of years-- get beaten down by "science". As I said, if you are uncomfortable using the herb, by all means, don't. Life is fatal, after all.

  • silversword

    "Life is fatal, after all."

    Thank you, Simple, for your brevity.

  • filaluvr

    Anyone want to share/trade for some comfrey seeds/cuttings? Thanks, Kathy in Texas

  • brendan_of_bonsai

    Anecdotes don't stack particularly well, over time or concurrently.

  • novice_2009

    Um, eric, do you work for the FDA or any pharmaceutical companies? Lol. It's late and I'm tired. Ever heard of quenn of hungary's water? So many external applications of comfrey leaf, it's unbelievable. My husband has excema, my brother-in-law psorasis, so if topical tx for them using some comfrey leaves works, what's the big deal? I never use it internally, and it's a lot safer than drugs put on market. This is crazy. Comfrey is safe in topical tx.

  • rusty_blackhaw

    As previously mentioned in this forum, knowledgeable herbalists are among those calling for comfrey not to be used on broken skin or open wounds, not to be used in any form in children, and especially not ever to be used internally.

    And no, I have no connection with the FDA or any pharmaceutical companies.


  • gringojay

    ? Is comfrey root suitable for internal use ?

  • rusty_blackhaw

    ""Comfrey root contains about ten times the concentration of (toxic pyrrolizidine alkaloids) found in the leaves."

    That's a quote from a highly respected herbalist, Varro Tyler, who has said that owing to toxicity and lack of evidence of effectiveness, "Comfrey has no place in our modern materia medica."

  • kaliaman

    imagine my surprise when a link to this thread showed up in a forum for professional medical herbalists today. the comments of the comfrey naysayers are getting good natured laughs and pokes from folks who actually know what they are talking about...and comfrey saavy folks are getting cheers for knowing their stuff! oh yeah : )

  • rusty_blackhaw

    Nice that some supposed professional herbalists are laughing about the risk of hepatotoxicity from consuming comfrey.

    When they get over their fits of the giggles, they can familiarize themselves with the views of many of their fellow herbalists, who agree that the questionable benefits involved in the internal use of comfrey do not justify the hazards involved. For instance:

    "By the mid 1990s herbalists stopped recommending the internal use of comfrey due to some chemicals that were found in comfrey that have been shown to have toxic effects on the liver".


    "...there are enough reasons to consider that using this herb or preparations containing it has a perilous effect on the overall health of the individual using it. In fact, various species of comfrey that have been examined by scientists so far have shown to contain hepatotoxic pyrrolizidine alkaloids (PAs)...ironically enough, majority of the comfrey grown in the home gardens are hybrids of the Russian comfrey. In fact, the roots of this herb enclose around ten-fold more of the pyrrolizidine alkaloids (PAs) intensity compared to what is present in the leaves...owing to the absence of chemical analysis, it is always not possible to correctly verify whether any remedial herbal product actually contains this toxic element. In fact, the commercial labeling system in the country is very undependable. It needs to be emphasized here that simply because the sale of products enclosing echimidine is banned in Canada, people should not underrate the possible perils of using common comfrey, which encloses other different hepatotoxic pyrrolizidine alkaloids (PAs). In general, sale of any product containing the comfrey roots are now not allowed in Canada."

    Still laughing?

  • HerbDoctor

    Perhaps the conflict here has to do with the way many people view the use of comfrey. For instance, I hear a lot of people who take a particular herb as they would a pharmaceutical; every day for months on end. This is an abuse of the intended use of herbs. Herbs should be viewed as food that can nourish the body. After a few days, a person should have fulfilled that nutritional need and stop taking the herb. But people think that they need to take it every day for a long period of time in order to subdue a particular symptom as they would a pharmaceutical. (I'm repeating myself)

    If people are taking comfrey over a long period of time, it would be reasonable that there could be some toxicity issues here especially with the presence of pyrrolizidine alkaloids.


  • craigs43

    Regardless of the back and forth, this was truly informative for me. I have a question, and I'm hoping someone can shed some light. I am looking to (also) use Comfrey as a salve. Is there an unsafe way of going about this? I am using coconut oil as the base. Thanks!

  • HerbDoctor

    Whether you use the root or the leaves, you have to decide on a stabilizing element to your salve. In other words, what are you going to add to the salve to keep the comfrey from rotting? Just putting it in coconut oil isn't enough.
    If you're thinking to go commercial with such a product, you have this problem to overcome. However, for personal use, the best thing to do is to keep dried, sliced comfrey root on hand and boil up a bit each time you need it.


  • rusty_blackhaw

    While amounts are said to vary considerably from plant to plant, in general the roots contain much higher concentrations of potentially toxic pyrrolizidine alkaloids than the leaves.

    If making up a comfrey salve for external use on unbroken skin, the leaves sound like a better bet.

  • HerbDoctor


    Though your comments carry a moment of truth, it doesn't approach the qualitative nor quantitative concerns for comfrey. You may avoid higher levels of p. alkaloids, but external use doesn't begin to approach toxic levels. Besides, there are therapeutic values in the root that you won't get in the leaves. Atleast, not in the levels necessary for a therapeutic application.
    I'm just speaking from experience.


  • sunlight33

    I would like to use comfrey root as a mouth rinse to look if it can cure my tooth decay. Some people seem to have very good results with it. Comfrey root was also one of the ingredients in Dr. Christopher's tooth powder before it was forbidden, and this tooth powder also seemed to work very good to cure tooth decay.

    I harvested some fresh comfrey root (in west Germany), sliced it up and dried it.
    Now I want to grind it in a coffee grinder and eather use is as a tooth brush powder of make a tea from the powder that I use to rinse my mouth. What would work best? I'm planning to do this about 2 months to see if it works.

    I read that drying comfrey reduced the amount of PA's, is this true?
    Is it possible that the PA's will enter the bloodstream through the oral mucosa when the comfrey root is used as a mouthrinse?

    Thanks in advance!

  • kaliaman

    the primary cause of liver failure in the united states is the use of NSAIDs, and in particular, tylenol. by far, without question. per the folks who keep track of such things.

    comfrey fears are real but way overblown.

  • rusty_blackhaw

    To clear up some misconceptions:

    First, comfrey does not have proven efficacy against tooth decay, either as a preventative or to reverse decay that's already underway.
    Safety as a mouth rinse is probably not a major concern apart from possible local irritation, if one is careful not to swallow any.

    Many responsible herbalists recommend against any internal use of comfrey because of the risk of pyrrolizidine alkaloid toxicity, implicated in some cases of acute liver failure and a concern for possible carcinogenicity. Oral formulations are banned in most countries for this reason. Young children are especially susceptible to toxicity from comfrey (even a few days of taking comfrey internally can be fatal).

    Contrary to what's been stated, acute liver failure is not a significant consideration when it comes to use of NSAIDS (non-steroidal anti-inflammatory drugs). Tylenol (acetominophen, which can be hepatotoxic) is not an NSAID (non-steroidal anti-inflammatory drug) like aspirin or Motrin. Tylenol is not an anti-inflammatory agent - it works by a different mechanism than NSAIDS to reduce pain and fever. Used in proper dosage and not combined with other things that can damage the liver (i.e alcohol) it is a generally safe as well as effective drug. The real problem is when people take too much, which may happen when they combine or otherwise overdose on over-the-counter cold meds.

    The big difference between Tylenol and comfrey is that Tylenol is a proven effective drug. Comfrey may have limited value in topical pain control (when applied for limited periods on unbroken skin), but in general the claims made for it have not been backed by quality studies (something to consider when weighing a decision whether to ingest it). You cannot count on drying to significantly reduce the harmful alkaloids. Unfortunately, you also can't count on comfrey sellers to be knowledgeable and upfront about the composition of their products in our current, largely unregulated supplement market.

    I rarely take acetominophen, but feel a lot more confident about its safety than I do comfrey. And based on what we've seen already, if Americans began to ingest comfrey as commonly as they do acetominophen, it's extremely likely that comfrey would quickly pass acetominophen as the leading cause of acute liver failure in the U.S.

  • sidemeat

    As with anything........moderation is the key. Too much of a good thing etc. Many drugs today are synthetics of the herbs. No money in that for big pharm or government.

  • rusty_blackhaw

    You're citing a 1936 book for guidance? I think we've learned a fair amount since then.

    "Many drugs today are synthetics of the herbs. No money in that for big pharm or government."

    This is a perfect example of a huge contradiction to which many alt med advocates seem oblivious.* Why on earth would so many drugs derived from or based on plant-based compounds be in existence, if there was no money in selling them?

    *these folks tell us on the one hand that many/most modern drugs are derived from plants, and in the same breath declare that no one in pharma will investigate plant-based drugs because they can't be patented. ;)

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