Queen Comfrey (Symphytum officinalis) – Shaking Off the Fear that Binds Us
- Posted on
- By Valerie Blankenship, RH, AHG
- 0

Comfrey is, and has been, an extremely popular herb throughout history – recorded for the past around 2,500 years and likely much earlier than our ability to trace. And for most of that time, her medicine has been used internally without safety concerns. But all that changed dramatically in the 1970s and 80s. At that time, scientists with questionable motivations and funding sources, began to mount controversies about 3 important herbs: ephedra, kava and comfrey – with the message that they were toxic and should never be ingested. Scientists sounded the alarm, declaring comfrey was not safe to ingest because it was found to contain a variety of Pyrrolizidine Alkaloids (PAs). The PAs were found in the fresh young leaves and in the root, but according to two separate investigations, not in the dried herb.
Pyrrolizidine alkaloids (PAs) are naturally occurring toxins found in a wide variety of plant species. PAs are produced as a defense mechanism against insect herbivores by plants. More than 500 PAs have been found in 200 different plants. All PAs are not all equal, with some being toxic and some harmless. It is well-known that PAs can be hepatotoxic, or harmful to the liver. Actually, to put it more specifically, some PAs can be harmful to humans, depending on the type of PA and the dose given. And of course, given as a pure extraction of a single PA, and injected into lab mice in massive doses, naturally this has been found to cause liver damage.
Queen Comfrey – Shaking Off the Fear that Binds Us
By Valerie Blankenship, RH, AHG
Like most herbalists, I have a profound respect and love for comfrey. As a medicinal herb, her powers are irreplaceable. She is moistening yet profoundly strengthening, giving yet self-nourishing, powerful yet deeply comforting, both wise and gentle, and deeply spiritual - grounded in her ancient medicinal self. She possesses gooey allantoin goodness that will straighten and strengthen the spine and tannins that tone and strengthen the skin. In fact, her powerful green leaves, crisscrossed with prominent veins, remind me of a healthy skin barrier. Her creative nature even extends to her deep blue flowers which curl flamboyantly like a scorpion’s tail.
We search for magic in a world that leaves us battered and bruised, and she brings her profound healing magic. Is there anything more magical than her mystical ability to knit bones together? She is the Supreme Weaver, able to sew together both our torn tissues as well as our shredded emotions. She is even able to heal herself – dig up her roots and she will easily mend herself and continue to grow unabated. Both of her names tell of her powers. Comfrey from “con firma,” which means “made firm” or “to boil together.” Her genus name, Symphytum is from the latin “symphis” meaning “to grow together or unite.” If you already know her, you may know her as Queen Comfrey. Both upper and lower parts of her she offers as medicine, both externally, as a vulnerary, as well as internally, for her demulcent, bone strengthening and nutritive powers. A magnificent Green Queen she is.
I have used comfrey internally many times myself as well as with clients. Some of the most dramatic healings I have seen were with clients who had internal abdominal injuries, ripped ligaments, traumatic births, severe varicose veins, bleeding ulcers, wrenched muscles, and multiple broken bones. A client years back who had shredded the ligaments in his shoulder from catching a heavy object, was given a tissue implant that failed, resulting in an autoimmune reaction that the doctors could not halt. I designed a protocol to calm the immune system and to heal the torn ligaments. Comfrey infusions were given to take daily until he was healed. He made me a video of his dramatic, fast and complete recovery which I will never forget. Many of my clients suffering from herpes infections have benefited from daily infusions of comfrey leaf. One client I remember from years ago was taking a preparation of herbs I had given him for a severe, tenacious genital herpes infection. This time, the herbs weren’t working fast enough to stop the blistering infection from bubbling up to the surface, causing a relentless breakout. Following my recommendations to take daily comfrey infusions, and after only the first 2 cups, his breakouts ceased abruptly and never returned. I have often been amazed and grateful at the power of comfrey when no other herb could adequately substitute. Many of my herbalist friends and colleagues have similar stories.
From Adoration to Fear
Comfrey is, and has been, an extremely popular herb throughout history – recorded for the past around 2,500 years and likely much earlier than our ability to trace. And for most of that time, her medicine has been used internally without safety concerns. But all that changed dramatically in the 1970s and 80s. At that time, scientists with questionable motivations and funding sources, began to mount controversies about 3 important herbs: ephedra, kava and comfrey – with the message that they were toxic and should never be ingested. Scientists sounded the alarm, declaring comfrey was not safe to ingest because it was found to contain a variety of Pyrrolizidine Alkaloids (PAs). The PAs were found in the fresh young leaves and in the root, but according to two separate investigations, not in the dried herb.
Pyrrolizidine alkaloids (PAs) are naturally occurring toxins found in a wide variety of plant species. PAs are produced as a defense mechanism against insect herbivores by plants. More than 500 PAs have been found in 200 different plants. All PAs are not all equal, with some being toxic and some harmless. It is well-known that PAs can be hepatotoxic, or harmful to the liver. Actually, to put it more specifically, some PAs can be harmful to humans, depending on the type of PA and the dose given. And of course, given as a pure extraction of a single PA, and injected into lab mice in massive doses, naturally this has been found to cause liver damage.
Fear of Comfrey Impacts Our Community
The effect of this research beginning in the 70s on the herbal community as well as comfrey users across the US and Europe was paralyzing. The grip of fear ushered in an era of self-doubt and self-censorship toward the internal use of comfrey that still stands today. I’ve heard many clients gasp at the mention of taking comfrey internally, as if it were actual poison they were being offered. I either educated them on the topic if they were open-minded, or dropped the topic entirely and chose a different protocol if I felt they feared comfrey too much to use it. Many of us felt, and still feel, the pressure. Myself, having been a frequent user of comfrey since the beginning of my herbal career 34 years ago, felt the uncertainty myself. I have gone back and forth over the years, mostly reserving internal use for severe conditions only until just a few years back, when I began to look carefully at the research and discovered that evidence that comfrey is not safe was not adequate to warrant my excluding it from internal use. Following the release of the PA research however, many herbalists and comfrey users that I know quickly extinguished their use of comfrey internally. Many of them decided that since the red flag of alarm had been raised by the scientific community, it should never be used internally.
Not long ago, a client of mine had a traumatic birthing experience. The birth process was long and arduous, and there was great difficulty in getting the baby out of the birth canal. Following the birth, the baby quickly healed, but the trauma of the birth left the mom unable to walk. Tests revealed a crack on either side of her sacrum. A few inches more and she would have been permanently injured and partially paralyzed. Although she used comfrey salve externally, the ingestion of healing infusions containing comfrey, even in small amounts, was out of the question. It took over 3 months before she was beginning to walk normally. How I wished she could have turned to comfrey to help mend her wrenched body. It likely would have sped up her healing, strengthened her body and given her much comfort.
10 years ago, I was in an immersion Spanish program in Costa Rica. One day, the husband of the family I stayed with, upon learning that I was an herbalist, ask me for help for his father. The man was a nurse, and his father was a patient in the hospital that he worked in. He was suffering from a rather large bleeding ulcer and the doctors were unable to staunch the internal bleeding from the open sore in his abdomen. In my first aid kit I had goldenseal root and comfrey root powders. Help was on the way! I knew the mixture would make quick work of healing the man’s father and that he would be amazed. I mixed the two powders and told him to give his father ½ teaspoon of the mixture in water, several times per day. Before giving him the herbal powders, I cautioned him about the negative information he would find on the internet about “Consuelda”, (the Spanish name for comfrey). The next day he returned and told me that his father was worse, but that he had learned from a doctor at the hospital that internal use of comfrey was deadly and although he did not know who to believe, he was afraid to give the comfrey. He was confused and upset that I had made the recommendation. I hope his father eventually healed, although I never heard.
Other herbalists, having used comfrey internally themselves and with their clients for many years without any problems or concerning issues, or had taken the time to dig deep into the research, knew that the research was problematic and did not warrant the discontinuation of comfrey. They didn’t trust the research and refused to discontinue the internal use of this powerful herb, nor were they willing to blacklist her. Instead, they stood up for our Queen Comfrey. Outspoken, well-known elders in the herbal community, who have taken Comfrey for many years without harm have come forward over the years. One of these herbalists is David Hoffmann, who I studied with over 30 years ago. David was the one who first taught me about the healing power of using comfrey internally without fear. In Susan Weed’s online Comfrey Conference time to end the fear (2022), [10], He was interviewed about the internal use of comfrey. He shared a formula that he had used many times with clients to heal ulcers:
Guideline from the British Herbal Pharmacopeia:
Peptic Ulceration:
To address the pain of the ulcer quickly:
Either use straight Comfrey root or:
Comfrey root – 2 parts
Marshmallow – 1 part (Marshmallow root really does add a quality of support to it.)
Chamomile infusion ad libidum
To actually heal the ulcer:
Comfrey root – 3 parts
Goldenseal root – 1 part
Chamomile infusion ad libidum
It should be taken at least 3 times a day or more.
The Spread of Fear Can Wreak Havoc
Following the 70s PA research, comfrey was banned from sale in the United Kingdom, Australia, Canada and Germany. What could be next? According to David Hoffmann, although there is no evidence that Europeans are dying of PAs, the European Union has a paper pointing out that PAs are dangerous. As a response they are suggesting that citizens tear out the historic hedgerows that surround their property which house small wild animals, insects and birds. “They are suggesting that people trim all of their wild plants, from the edges of your property. This is supposed to keep PAs from contaminating the wheat in nearby farms”. He points out that “One of the last places where there is some biodiversity left are the edges of fields. Where they are going with this is making the crisis of climate change worse because of meaningless paranoia. PAs get blown around from field to field. But it is impossible for them to contaminate plants. So the implication is that you should never buy herbs or supplements because they could be contaminated. To turn that into legislative guidelines is just ridiculous. “
Comfrey Fear is Rampant on the Internet
Regardless of a lack of evidence proving comfrey to cause harm when ingested, the public, as well as herbalists, are frequently subjected to misleading information about the dangers of comfrey circulated through various formulaic articles posted on the internet. As just one example of many: Healthline recently posted an article entitled “The Risks of Eating Comfrey”, in which it was stated: “Today, eating or taking any form of comfrey by mouth isn’t recommended. It’s considered unsafe, due to the pyrrolizidine alkaloids that comfrey contains. These are dangerous chemicals that can cause cancer, severe liver damage, and even death when you consume them. For this reason, the Food and Drug Administration and European countries have banned oral comfrey products.” This is misleading and untrue. The actual fact is that the Food and Drug Administration (FDA) released an advisory in July 2001 recommending that comfrey products be removed from the market based on the faulty PA research done.
Examining the Faulty Research – a Closer Look
Long-term rodent studies showed PAs found in comfrey to be hepatotoxic, carcinogenic and mutagenic at an extremely high concentrations of 5x10 -3M. In one study, an extract of pure symphytine PA was used. Male rats were injected with 13 mg/kg twice weekly for 4 weeks and then once a week for 52 weeks. All 20 rats developed liver disease. The equivalent in human risk would be between 15-2,288 pounds of dry leaf per dose, if you assumed 5% of comfrey PA is symphytine. This is an example of a typical PA mouse study, which cannot be used to determine human risk, as the dosing was 100 – 10,000 times greater in the rat study than in real life oral usage by humans or animals. [1]
Looking at the research, it is important to note that this none of the individual PAs have been shown to be toxic, in quantities in which they appear in whole plant material, at common human doses. The two major PAs, lycopsamine and intermedine, have not been shown to be hepatotoxic at all, even when given as a single injection to 2-week old rats at doses up to 60 and 120 mg/kg This would be equivalent to 8,181 milligrams or about 16 “00” capsules per day of the extracted PAs taken by a 150-pound person. It didn’t even have any absorbable toxicity to the potato beetle and noctuid month larvae. [2] [3]
Human Studies Show Comfrey to be Safe
Prior to the PA studies of the 70s and 80s, comfrey leaf was a readily available herb for sale in the US and UK and was a popular tea in which many people had been ingesting for many years. An interesting study was conducted that set out to determine if occult (hidden) liver damage was present in a small group of 29 people who had been using it on a long-term basis. The study subjects had been using 0.5 - 25 grams (equivalent to about 1-50 cups of infusion/capsules/tincture) of comfrey leaf per day for 1-30 years. The researchers measured aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT), bilirubin, and alpha-fetaprotein (AFP) as markers of liver inflammation, liver disease and cancer. All measurements for all study group members were within normal limits and no sign of disease was observed. [9]
Comfrey Poisoning Reports do not Show it to be Unsafe
A clear link has never been found between liver damage and the consumption of whole comfrey. There are only five poisoning reports involving people who were taking comfrey. All of those cases occurred between 1980 and 1990. The cases involved varying doses combined with other medications and/or preexisting medical conditions. There have only been 2 verified incidents of PA poisoning casing death, one in Ethiopia and one in Europe neither of them from Comfrey. The last incident occurred over 50 years ago.
The research to demonstrate potential toxicity from ingesting comfrey simply does not exist.
A thoroughly researched, balanced review of the toxicity potential of comfrey by Dorena Rode “Comfrey Toxicity Revisited” 2002 [4], reveals a lack of evidence to implicate comfrey using neither the established research, nor in any of the case reports of liver damage. Dorena concluded that the evidence to convict this multitalented plant as hepatotoxic is lacking. Her conclusion was based on the following reasons which I have paraphrased:
- Purified PAs were the substances used in most of the studies, and these don’t reflect the actions of the whole plant. We can conclude that these studies way over-emphasize the risks of using whole plant extracts or the whole plant itself.
- The dosing was way too high, (at times thousands of times higher than typical human dosing) my words.
- Not all animals suffer ill effects from ingestion of PAs. The vast majority of the unwilling subjects of the PA studies were rodents, who are known to display different reactions to PA poisoning than humans or even other animals. For example, rabbits commonly eat Senecio species plants containing PAs with no health problems but are killed from a single injection of purified PAs [8]. Pigs show nothing but an increase in health when comfrey is eaten as 40% of their regular diet.
- The rats were injected with the pure PA extracts. This method of ingesting PAs is known to increase toxicity.
- All of the 5 case reports had extenuating factors including liver disease, use of OTC hepatotoxic medications such as acetaminophen, or protein deficiency, that could have all be contributors to liver damage.
- Lastly, research or case reports involving PAs from plants other than comfrey can’t be used as credible evidence against comfrey as the toxicity of PAs varies greatly based on each specific PA. In other words, not all PAs have the same toxicity.
Comfrey is More Than a Sum of its Parts
It is important to note that a plant cannot be reduced to its individual parts to prove that one constituent is toxic and thereby conclude that the entire plant is toxic. Comfrey does not contain merely PAs. It contains a whole matrix of constituents. As David Hoffmann writes in his book “Medical Herbalism”, the average cup of fresh comfrey leaf tea may contain up to 8.3 mg of PAs, far lower than the amount forced into rodents during the PA experiments. In his book, he gives preparation and dosage information for tincture, decoction and cold infusion of dried comfrey roots. In his article “Is Comfrey Safe?” he emphasizes the lack of evidence that comfrey is unsafe. “Comfrey is not simply a vehicle for the pharmacological effects of a specific constituent. The herb’s pharmacological effects are far more complex than that. The fact that PAs pose risks cannot be simply used by extension to imply that comfrey is an unsafe herb.”
Whole Plant Research Turned up Anti-Cancer Properties in Comfrey
Contrary to research using administration of high dose PAs, a research study done in 1963 discovered a protective effect from Comfrey leaves which were prepared in the traditional manner, through cold-water extraction. In the study, 71 control and 63 experimental animals bearing transplanted mammary tumors were given comfrey infusion. The survival of the tumor-bearing mice that received the cold-water comfrey extract was increased by an average of 59% as compared with the controls. Their tumor weight at autopsy was 24% less in the comfrey mice as compared with the controls. Pretty exciting stuff, huh? Besides the fact that ugg, I just hate the horrors of animal research, don’t you? But this research has been overshadowed by the fear of one constituent.
Not all Plant Parts are Equal
The research on Comfrey did bring up some valuable information for herbalists and consumers of the herb. It was discovered that the amount of PAs varies depending on the growth state of the plant. Small young leaves were found to contain higher concentrations of PAs than larger leaves later in the season. [5] Within the roots, the PAs are concentrated in the smaller young roots [6]
Is Comfrey Held to an Impossible Safety Standard?
In an article entitled “Is Comfrey Safe?” David Hoffmann brings up the topic of what is known as the therapeutic index. This measurement weighs the beneficial effective dose of a drug or herb to a toxic dose of a substance. The relative safety of a drug or herb is based on any possibility of risk compared to the benefits provided. There is simply no clear evidence that comfrey leaf or even root is toxic when taken orally. It does contain a variety of PAs, the majority of which are not toxic. Others, if isolated or taken in enormous quantities, can be harmful. But the evidence that typical historical as well as modern dosing, from several caps, droppers, or cups of infusions taken once or several times per day, is non-existent.
As a comparison to the way comfrey is held to an much different safety standard than OTC drugs, let’s look at Tylenol (acetaminophen), a common OTC pain and fever reducer. When taken occasionally and within recommended doses, it is considered to be safe. However, frequent use, chronic use, or even one large dose, can cause liver damage. The warnings for Tylenol are not to never ingest it internally, but to not exceed the recommended dose, to avoid drinking alcohol while taking it, and to check to see if you are taking it from different sources which could add up to an overdose. In the case of comfrey, we need to assess how the benefits compare with the risks.
In his article, “Is Comfrey Safe?” [7], Hoffmann brings up other issues to consider when assessing herb safety, including:
- Has traditional use of the plant revealed any knowledge of toxicity?
- Does the plant contain constituents with established toxicity?
- Does objective data for both toxicity and efficacy exist? Are the research results valid enough to form some basis for approximate risk assessment?
- How does the science compare with the perceived risk expressed by the FDA, practitioners of orthodox medicine, or herbalists?
Hoffmann wisely implores herbalists not to jump to conclusions about herbal contraindications from research if:
- They are derived from animal experiments
- The studies use isolated constituents instead of whole plants
- They disagree with established phytotherapeutic experience and protocols.
LET’S REVIEW
FACT: Comfrey contains a variety of PAs.
FACT: Some PAs, if isolated and consumed or injected, at doses 100 or more times the normal dose, can be toxic.
FACT: No studies have been done to compare the toxicity of isolated comfrey PAs to a whole plant preparation.
FACT: Rodents are more susceptible to injury from PAs than humans.
FACT: Comfrey plant contains lots of constituents, not just PAs
FACT: Comfrey has been historically used without signs of liver or lung damage, for around 2,500 years.
FACT: The FDA is in bed with big pharma. They don’t like powerful herbs that threaten to compete for pharmaceutical dollars.
FACT: Big pharma does not like the powerful benefits and lack of toxicity of herbal medicines to overshadow their chemicalized medicines.
Are Herbalists Allowing Unwarranted Fear to Control Us?
As herbalists, we have enough to contend with from the FDA, who are clearly in bed with big pharma. More than ever, the FDA is breathing down the necks of herbal companies, searching our websites for claims, either based on research, historical fact, or personal or customer experience. The war has been waged, mainly though social media censorship, to hinder our ability to educate the public about the health benefits of herbs. Considering this all-out attack, shouldn’t we question this censorship as well as the blacklisting of herbs? And shouldn’t we think twice before we censor our own selves from using an incredibly powerful herbal ally based on inconclusive evidence?
There is currently no FDA regulation that says we have to have a label comfrey products “not for internal use.” In the Comfrey Conference, David Hoffmann stated “there is no regulation that says we have to have a label with a big caution that it should not be taken internally. That is our community that is doing that. We are agreeing with what scientists say, not with what the SCIENCE says. We should question ourselves for buying into this misinformation.” The warning against comfrey’s PAs is now being applied to Boneset, Petasites, and Coltsfoot. Where does the fear end? What herbs will be torn from our materia medica and our apothecaries next? Will we comply? Will we accept poor quality scientific studies that seek to cast doubt on our most powerful herbal allies? Will we tear the herbs out of our gardens ourselves? Or will we stand up against the blacklisting of herbs with established historical use and exemplary safety records?
Finally, we should all make up our own minds about taking comfrey internally. We must ask ourselves: do scientists know more about the safety of herbs by taking plant chemicals apart, injecting some of those chemicals into rodents, than we, as herbalists, know from years of our own use and a millennia of traditional use? For those of us who have decided that the PA studies do not prove that comfrey is unsafe for internal use, and have chosen to use and recommend comfrey internally, many of us, myself included, are using a similar set of guidelines just to stay to the extreme left of even the lowest possibility of toxic exposure.
Most of us, out of an overabundance of caution, recommend internal dosing of no more than around 1 cup of infusion/capsule/dropper of comfrey, up to 2 x per day for no more than about 4 days per week. Some may say no more than 1-3 months at a time. Some see no need to limit the length of time comfrey is ingested. Most of us recommend avoiding comfrey altogether in those who have a compromised liver. But it is critical for the future of herbalism, including future herbal damnations from the scientific community, to decide not based on fear and ignorance. Let’s take into consideration the scientific evidence, or lack thereof, the 2,500 years of historical use of comfrey as both an internal herbal medicine as well as a forage crop, and finally we must check in with our inner wisdom and guidance before we decide to cast out one of our most valuable herbal healing gifts.
[1] Culvenor, C.C., et al., Structure and toxicity of the alkaloids of Russian comfrey, a medicinal herb and item of human diet. Experientia 1980. 36(4): p. 377-9
[2] Reina, M., et al., Pyroolizidine alkaloids from Heliotropium megalanthum. Journal of Natural Products, 1998. 61 (11): p. 1418-20.
[3] Culvenor, C.C., et al., Hepato- and pneumotoxicoity of pyrrolizidine alkaloids and derivatives in relation to molecular structure. Chemico Biological Interactions, 1976. 12(3-4): p. 299-324.
[4] Rode D. Comfrey toxicity revisited. Trends in Pharmalogical Sciences 2002; 23:497—9.
[5] Mattocks, A.R., Toxic pyrrolizidine alkaloids in comfrey [letter]. Lancel, 1980. 2 (8204); p. 1136-7.
[6] Muetterlein, R. and C. – G. Arnold, Investigations concerning the content and pattern of pyrrolizidine alkaloids in Sympytum offinale L. (Comfrey). PZ (Pharmazeutische Zeitung) Wissenschaft, 1993. 138(5-6): p. 119-125.
[7] Hoffmann, D, Is Comfrey Safe? http://herbcraft.org/hoffmanncomfrey.html
[8] Pierson ML, et al. Resistance of the rabbit to dietary pyrrolizidine (Senecio) alkaloid. Research Communications in Chemical Pathology and Pharmacology 1977; 16:561—4
[9] Anderson, P. and A.E.M. McLean, Comfrey and Liver Damager. Human Toxicology, 1989. 8 (1): p. 68-69
[10] Susan Weed’s online Comfrey Conference 2022 available for download https://www.ashtreepublishing.com/comfrey-conference
Other research used to write this article:
Röder E. Medicinal plants in Europe containing pyrrolizidine alkaloids. Pharmazie 1995; 50:83—98.
Rothschild M, Edgar JA. Pyrrolizidine alkaloids from Senecio vulgaris sequestered and stored by Danaus plexippus. Journal of Zoo and Wildlife Medicine 1978; 186:347—9.
Schneider D, Boppré M, Schneider H, et al. A pheromone precursor and its uptake in male Danaus butterflies. Journal of Comparative Physiology 1975; 97:245—56.
Beers MH, Berkow R, eds. The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 1997.
Stickel F, Seitz HK. The efficacy and safety of comfrey. Public Health Nutrition 2000; 3:501—8.
Comments
Be the first to comment...