Botanical: Symphytum officinale
parts used: aerial parts, root
actions: anti-inflammatory, anodyne, demulcent, mucilagenous, nutritive, styptic, vulnerary
Comfrey is a perennial herb with a black, many fingered root and large, hairy broad leaves that bears small bell-shaped flowers of various colours. The flower color on our plants is a light beautifully streaky purple. The botanical name for comfrey, Symphytum, means “to unite” or “grow together.” (from the Greek symphis, meaning growing together of bones, and phyton, a plant). This gives a clue to the ancient use of this wonderful herb.
To differentiate it from other members of the genus Symphytum, this species is known as common comfrey or true comfrey. Other English names include blackwort, bruisewort, consormol, consound, knitbone, and slippery root. Note: this is NOT Russian comfrey (the ‘Bocking 14’ cultivar).
One of comfrey’s many folk names, knitbone, says it all, and modern studies have demonstrated that comfrey is a medicine with genuine merit. Randomized controlled trials have shown that topical use is effective at treating injury, arthritis, and inflammation.
Researchers have identified a compound called allantoin which explains at least some of how comfrey heals. Allantoin makes cells grow, giving rise to new collagen, connective tissue, and bone.
Using Comfrey in the Garden
Comfrey’s deep roots work to bring nutrients up from the subsoil. These nutrients are then made available in the abundant number of leaves it produces every year (4-5 lbs of leaves per established plant/ per year). The leaves are rich in nitrogen and potassium with a decent amount of phosphorus as well, making them a wonderful homegrown fertilizer. Researchers in British Columbia analyzed the NPK (nitrogen-phosphorus-potassium) ratio of comfrey* and discovered that the leaves have a remarkable NPK ratio of 1.80-0.50-5.30. When we compare these nutrient ratios to that of animal manure we can see how far superior comfrey is. 
Dairy Cow: .25-.15-.25
Note: Naturally, nutrient values of animal or plant based manure can vary greatly from specimen to specimen. * Air-dried powdered comfrey leaf tissues.
Comfrey grows best in soggy and marshy areas, but extremely moist conditions are not necessary to grow excellent plants. Comfrey prefers a sweet soil with a pH of 6.0-7.0 and grows best in rich, moist soil in full sun, but will tolerate some shade. It will grow well in clay or light sandy loam; in dry or wet areas. It adapts well to most any environment growing strong with deep roots. It can be propagated from its seeds during spring or by root division during autumn. The leaves and the flowering aerial parts are usually collected during the summer months. The root of comfrey is harvested during autumn.It also casts doubt that comfrey can cause cancer outside of laboratory experiments, and states that a toxicological study has shown that normal human use of comfrey cannot cause death or toxicity. Click To Tweet
Using Comfrey for Wellness
Comfrey salve is typically used as a topical herbal remedy for painful muscle and joint conditions, such as low back pain, osteoarthritis, and sprains. It’s also used in alternative medicine for the following problems:
- Rheumatoid arthritis
- Sprains and strains
Here’s a look at some key findings on the potential health benefits of comfrey oil or salve:
Comfrey salve could help ease back pain, suggests a 2010 study from the British Journal of Sports Medicine. The study included 120 patients with acute upper or lower back pain, each of whom were treated with comfrey ointment or a placebo for five days. Study results revealed that pain intensity decreased an average of 95.2 percent in the group given comfrey ointment (compared to 37.8 percent in the placebo group). 
Comfrey contains an element called allantoin. Allantoin encourages cell growth and, thereby, aids in mending damaged tissue. Many of the beneficial properties of comfrey are attributed to its high content of allantoin, a substance that helps promote new skin cell growth.  In addition, the herb contains rosmarinic acid and additional phenolic acids that enable comfrey to function as an anti-inflammatory agent.
Topical comfrey root is superior to diclofenac (NSAID) gel in the treatment of ankle distortions. 
According to Susan Weed, “Comfrey leaf infusion is a classic for restoring good functioning to mucus surfaces, such as the lungs.” 
The results suggest that the comfrey root extract ointment is well suited for the treatment of osteoarthritis of the knee. Pain is reduced, mobility of the knee improved and quality of life increased. 
I highly respect the words of Heather Nic an Fhleisdeir who states…
Also, As trained herbalists we learn how to harvest and prepare herbs for best effects. Herbs with PA alkaloids traditionally are harvested and extracted in ways that would avoid the peak of concentration and extraction of PA’s.
Another way to obtain lower PA’s is that we know that PA’s are not very water soluble, and so drying these herbs and making herbal infusions is traditionally how they are used. Tinctures of these herbs are made from fresh plant material, using low alcohol content, such as 40% alcohol, which is 80 proof. The resultant tincture tends to be 30-35% alcohol in its finished state, depending on juiciness of the herb. If you follow both science and tradition it is evident that they often confirm and validate each other, especially when it comes to using herbs that contain PA alkaloids. 
Throughout history, comfrey has been used to heal wounds in battle, and was used extensively in World War I to treat maggot-infested wounds. Early American herbalist Samuel Thomson claimed to have used comfrey to heal his foot from a farm equipment accident when he was only 9. You can read more about this extremely influential herbalist at the School of Modern Herbal Medicine with Steven Horne and Thomas Easley.
Some herbalists still use it today to treat leaky gut syndrome— a condition where substances that are supposed to stay in the intestines leak into the blood stream. Comfrey is said to patch the holes in the gut.
When we say comfrey oil, we are talking about “infused” oil, not essential oil. Infused oil is simply herb soaked in oil for a length of time or over low heat to extract the herbs constituents into the oil. An essential oil is a concentrated hydrophobic (repels water) liquid containing volatile (easily evaporated at normal temperatures) aroma compounds from plants.
- For skin rashes – Comfrey oil can help in treating rashes. However, caution should be taken when it comes to deep wounds – the oil can help heal the skin so quickly that the new tissue may cover the wound before deep healing inside, resulting in an abscess or skin infection. 
- As a poultice – A poultice is a good alternative if you have an infection but don’t want to apply comfrey oil directly. Here’s how to do it: blend four cups of chopped leaves and stems with one-fourth cup of carrier oil, such as jojoba, almond, or olive oil. Without straining out the herb, wrap the comfrey oil paste with a cotton cloth. Freeze this poultice to help reduce pain and inflammation. Otherwise, you may apply it directly on the affected area for at least 30 minutes.
- For bone fractures – Apart from helping treat superficial wounds, comfrey oil has also been applied to fractured bones or torn ligaments in areas of the body where it is not possible to place a cast, such as a rib. It can be applied directly onto your skin or in a poultice, potentially promoting fast healing. It is also said to help reconstruct torn muscles that might have been injured.
” ‘But these are weeds, Sister. Weeds for broken bones and burns?’ The poultice was finally ready, and Gunnhilde knelt beside the boy’s head.
‘These are not weeds, Brother Cuillin, they are weapons in God’s armory.’ “
~ The Island House, by Posie Graeme-Evans
Is Comfrey Safe?
For starters, please listen to what the HomeGrown Herbalist has to say about it…
Comfrey oil appears to be safe when applied to unbroken skin.
It is “discussed” as unsafe to take comfrey by mouth because of its pyrrolizidine alkaloids (PAs), which it is proposed, can cause liver damage. The US Food and Drug Administration (FDA) has recommended banning oral forms of Comfrey.
However, in the Garden Web community forum, (now Houzz) Garden Web it was argued that the pyrrolizidine alkaloids (PAs) in comfrey are qualitatively and quantitatively less than toxic than those found in known poisonous plants, such as ragwort.
It also casts doubt that PAs cause cancer outside of laboratory experiments, and states that a toxicological study has shown that normal human use of comfrey cannot cause death or toxicity. Emphasis mine.
During studies undertaken to ascertain the elements present in comfrey, scientists have noticed that when pyrrolizidine alkaloids are present as solitary substances, they are extremely poisonous to the liver. However, the scientists are yet to ascertain whether pyrrolizidine alkaloids are also toxic when using the entire plant. In any case, they are present in tiny quantities in comfrey and sometimes they are totally lacking in samples of the dehydrated aerial parts of the plant. It has been found that the greatest intensity of pyrrolizidine alkaloids is in the roots of the plant.
Hence, until the time the scientists are able to validate or deny the safety of using the comfrey roots, it is not recommended to use the roots or herbal products enclosing them for internal use. However, it has been established that internal use of the aerial parts of the comfrey plant is harmless. Many herbalists are of the view that the legal question raised over the safety of using comfrey as a medication requires being secured by undertaking a more profound perception of the herb’s healthful aspects. I couldn’t agree more.
This may be long for an “Materia Medica” but Charles W. Kane in his book, Herbal Medicine, Trends and Traditions wrote…
As with most medicinal plants used today, if objective scientific research is applied, their traditional uses are substantiated or at least clarified. in Comfrey’s case, due to a configuration of events, the research that today is used to site Comfrey as a toxic plant was and still is mis-appplied. The short story, that an array of PAs found within Comfrey are harmful agents and a number of hapatoxic cases have been linked to the plant’s usage should be looked at more closely.
- Not all PAs are created equal. Depending on the family – genus – species, some PA-containing plants are completely non-toxic (Echinacea) or are overt poisons (many Senecia species). These differences are due to the type of contained PA. The American garden variety falls more to the non-toxic side of the continuum, whereas Russian varieties contain higher percentages of the more toxic PA, senecionine.
- The few cases of hepatotoxicity that were “reported” for Comfrey use in the lated 80s/ early 90s mainly involved individuals who had pre-existing liver-centered illnesses, and/or who who were users of hapatotoxic drugs. At least one individual ingested an extraordinary amount of the herb daily (10 cups of tea/”handfuls(s) of tablets daily) – a huge dosage for anyplant.
- Comfrey toxicity is mainly theoretical and is essentially based only upon animal studies. Purified PA fractions (not Comfrey) were fed to rats, who then developed hapatotoxic reactions. High administered PA to body weight ratio, and the fact that not all animals process PAs the same, factor into the alarmist result. Pigs, cows, chickens, and horses are less sensitive to PAs than rats, rabbits, goats, and sheep.
- Where do humans fit in? The fact is we don’t really know, but the most likely the situation with Comfrey is not as dire as some would suggest. Some perspective is needed. How many individuals die each year of liver-related pharmaceutical/over-the-counter poisonings? Hundreds, if not thousands. How many individuals have succumbed to the rational use of only Comfrey, with no pharmaceutical/prior disease history… zero!
- Comfrey’s overall usage history is so empty of toxicity report, it is strange that an apparent concentration of cases developed when they did. With some speculation it is not far-fetched to suggest that the few individuals supposedly affected by “Comfrey toxicity” were stricken, despite, not because of Comfrey. 
One last thing from Charles W. Kane’s notes…
I find it remarkable, yet typical that an individual can be on an organ transplant list, taking a slew of pharmaceuticals, drinking alcohol to excess just to dull the misery of the situation AND taking an herbal remedy. If the individual dies due to precarious health, guess who is blamed for that person’s death… you betcha… the herb. 
I love Charles Kane’s books.
In an old issue of Let’s Live (Oct.-Dec., 1958), H. E. Kirschner, M.D., wrote an almost unbelievable article about several important clinical uses of Symphytum officinale.
Dr. Kirschner used comfrey in his medical practice to promote the healing of ulcers and wounds. He traces the history of comfrey back to 1568 and W. Turner’s Herball which said “of Comfrey Symphytum, the rootes are good if they be broken and dronken for them that spitte blood, and are bursten. The same, layd to, are good to glewe together freshe woundes. They are good to be layd to inflammation…” He then cites Gerard’s 1597 Herball, which indicated comfrey for ulcers of the lungs and ulcers of the kidneys, and Parkinson’s 1640 Theatrum Botanicum:
“The rootes, taken fresh, beaten small, spread upon leather, and laid upon any place troubled with the gout, doe presently give ease of the paines and applied in the same manner, giveth ease to pained joynts, and profiteth very much for running and moist ulcers, gangrenes, mortifications and the like.”
Most significant is a citation from Tournefort’s 1719 Compleat Herbal, which tells of one who “cured a certain person of a malignant ulcer, pronounced to be a cancer by the surgeons, and left by them as incurable, by applying twice a day the root of comfrey bruised, having first peeled off the external blackish bark or rind; but the cancer was not above eight or ten weeks standing.” Even allowing for a misdiagnosis, this account is interesting.
Dr. Kirschner personally observed the powerful anticancer effects of comfrey on a patient of his who was dying from advanced, externalized cancer. He prescribed fresh, crushed-leaf comfrey poultices throughout the day. He writes that, “Much to the surprise of the patient and her family,” there was obvious healing within the first two days of treatment, with continued visible improvement over the next few weeks. “What is more,” he writes, “much of the dreadful pain that usually accompanies the advanced stages of cancer disappeared,” and there was a dramatic decrease in swelling.
Dr. Kirschner concludes by regretfully saying that the cancer had already spread to the inner organs “which could not be reached with the comfrey poultices, and the woman died.”
Just in terms of quality of life, the degree of healing that did occur under the comfrey poultice treatment is of tremendous significance. Here is a “folk” remedy undeniably providing, at the very least, significant palliative relief, and to a remarkable extent reversing a cancerous growth. We can ill afford to overlook the full potential of external comfrey leaf poultices to heal sores and wounds of all types, including burns and gangrene, as well as “tumors both benign and malignant,” says Dr. Kirschner.
Taken internally as decoction (boiled root tea), Symphytum officinale is described as effective against tuberculosis, internal tumors and ulcers, and promotes the healing of bone fractures. If it is hard to understand how one simple, easy to grow and easy to apply plant can be so widely useful in healing, remember that penicillin’s supporters have made some pretty broad claims for the mold on oranges. 
Note: I would like to add that I would copy his entire article here for you to read, but it is copywrited. So please do yourself a favor if you would like to know more about using this herb and visit his website. (link in credits)
Before leaving the wide comments relieving comfrey of its currently diminished status, I quote
Barbara Griggs and Bruce Ames (as quoted by James Duke PhD)…
Teas, almonds, apples, pears, mustard radishes, and hops, to list only a few items, all contain substances which, if extracted, can be shown to be poisonous when tested under conditions similar to those used in the comfrey experiments. Must we then ignore our experience of the usefulness and wholesomeness of these foods because controlled trials and scientific evidence have not been published to establish their safety? 
Other data supporting the relatively low toxicity of comfrey was published in the journal of Science by noted biochemist Bruce Ames, Ph.D., of the University of California at Berkeley, indicates that comfrey leaf tea is less carcinogenic than an equivalent amount of beer. 
The Washington Post article quotes Mark Blumenthal, president of the American Botanical Council, (one of eight groups that received the FDA letter being discussed as saying…
The agency failed to distinguish Russian and prickly comfrey, which contain liver-toxic chemicals, from common comfrey, which lacks them. The agency failed to point out that comfrey’s root has about 10 times the alkaloids as its leaf, and didn’t acknowledge that alkaloid-free comfrey extracts are available.
The FDA did not cite any new proof about comfrey in its letter, nor did it mention recent cases of comfrey-related poisoning and FDA’s Christine Lewis, who wrote the letter, says “it’s not clear there is a consensus against internal use of the herb. Our concern is the unsafe ingredients out there”
James Duke, former chief of the U.S. Department of Agriculture’s medicinal plants research laboratory, thinks otherwise. Duke, who grows comfrey in his garden, says
It (comfrey) is an excellent herb externally and very unlikely to cause problems internally. It does contain traces of pyrrolizidine alkaloids, and anyone eating it like spinach three times a day for 10 years might have a problem, but nobody in their right mind is going to do that.”
Video! Herbalists Rosemary Gladstar, Michael Tierra and Brigitte Mars discuss the benefits and uses of comfrey herb, also known as knit bone. Concerns about pyrrolizidine toxicity are addressed.
Susan Weed discussing true comfrey (Symphytum officinale) and concerns about pyrrolizidine alkaloids.
“If those of these times would but be, by a joint concurrence, as industrious to search into the secrets of the nature of herbs, and make trial of them. They would no doubt find the force of simples many times no less effectual, then that of compounds to which this present age is too much addicted.”
– William Cole, Adam in Eden
- Rodale Guide to Composting Rodale Books; Revised, Updated edition (June 5, 2018)
- Rodale’s Illustrated Encyclopedia of Organic Gardening: The Complete Guide to Natural and Chemical-Free Gardening
- David Hoffmann “The New Holistic Herbal” A Safe and Practical Guide to Making and Using Herbal Remedies, April 1, 1996
- Giannetti BM, Staiger C, Bulitta M, Predel HG. Efficacy and safety of comfrey root extract ointment in the treatment of acute upper or lower back pain: results of a double-blind, randomised, placebo-controlled, multicentre trial. Br J Sports Med. 2010 Jul;44(9):637-41.
- Phytomedicine. 2005 Nov;12(10):707-14. PMID: 16323288
- Weed, Susan, Wise Woman Wisdom, newsletter June 2008 http://www.susunweed.com/herbal_ezine/June08/wisewoman.htm
- Phytomedicine. 2005 Nov;12(10):707-14. PMID: 17169543
- Pyrrolizidine Alkaloids in Healing Herbs, Heather Nic an Fhleisdeir August 8, 2013
- Charles W. Kane, Herbal Medicine, Trends and Tradition by Lincoln Town Press May 1, 2009
- This is the writing of Andrew Saul, DOCTOR YOURSELF: Natural Healing that Works (webpage http://www.doctoryourself.com/comfrey_herb.html)
- Griggs, Barbara Green Pharmacy Healing Arts Press 1997
- Duke, James A. Ph.D. Handbook of Medicinal Herbs, CRC Press 2002
- Comfrey: A Healing Plant With a Misguided Reputation By Conan Milner, Epoch Times September 1, 2016
- MacAlister, C. J. and Titherley, A. W. (1936) Narrative of an Investigation Concerning an Ancient Medicinal Remedy and its Modern Utilities Together with an Account of the Chemical Constitution of Allantoin. London: John Bale, Sons, and Danielsson.
Here is a link for even more detailed study and General Information about Pyrrolizidine Alkaloids: Comfrey Central – A Clearinghouse for Symphytum Information