"However, while information is generally lacking to establish a cause-effect relationship between comfrey ingestion and observed adverse effects in humans, the adverse effects that have been seen are entirely consistent with the known effects of comfrey ingestion that have been described in the scientific literature."
- Food and Drug Administration press release, July 6, 2001
When I owned my health-food store in the Hudson Valley, one of my favorite customers was the Bear Mountain Zoo. Susie, the zookeeper, would buy a pound of catnip at a time for Bobby, the bobcat, since they wanted to keep him extra happy. (I harvested it fresh from my own herb garden.) One day Susie came in, very upset, because Molly, the porcupine, had eczema on her little tummy and asked for something to heal the irritated skin since Molly was so “cuddly.” (Yes, I wanted to know too how one cuddles a porcupine; they put a towel over her quills and let her snuggle up on the zookeeper’s lap.) I told Susie to come back the next day, and that night, I made up a nice, big batch of my comfrey healing salve. When treating animals (or small children), the first consideration is that they’ll lick and ingest whatever you put on them. Therefore, you must be certain of the healing balm’s safety, every consequence of any treatment pre-stirred in the herbalist’s brainpan.\
Powerful Remedy
In his original 1939 Back to Eden, Jethro Kloss explained that comfrey (Symphytum officinale) is “a powerful remedy in coughs, catarrh, ulcerated or inflammation of the lungs, consumption, hemorrhage, excessive expectoration in asthma, and tuberculosis. Very valuable in ulceration of the kidneys, stomach or bowels, or when sore … A poultice of the fresh leaves is excellent for ruptures, sore breasts, fresh wounds, ulcers, white swellings, burns, bruises, and sores … gangrene, mortifications, and moist ulcers.”
Even today, Dr. James Duke writes in The Green Pharmacy Herbal Handbook that the therapeutic uses include arthritis, bedsores, bronchitis, colitis, eczemas, gastritis, gum disease, hemorrhage, inflammation, intestinal inflammation, psoriasis, rashes, sores, and wounds. Some uses are internal and some are external. (A major New York City hospital sends home new mothers with a tea containing comfrey to help speed their childbirth healing.) Dr. Duke further states, “Not for long-term internal consumption … comfrey contains pyrrolizidine alkaloids, which in excessive amounts have been linked to severe, even lethal, liver toxicity. The warnings have given comfrey a bad rap.”
Pyrrolizidine Alkaloids
It is the pyrrolizidine alkaloids (PAs) that are of medical interest because they “have been shown to cause” a toxic reactions in humans. In studies, huge, isolated amounts of PAs demonstrated their toxicity by destroying liver cells or by causing abnormal cellular growth. This cellular-damage residue aggregates and can result in hepatic veno-occlusive disease (HVOD) and/or eventual liver cancer.
“The PAs, which have minimal toxicity in their original form, are metabolized in the liver and can become toxic metabolites, depending on the PA and on the particular condition of the liver enzymes.” (emphasis added) (Huxtable RJ and Cooper RA, “Pyrrolizidine alkaloids: Physiochemical correlates of metabolism and toxicity,” in Tu AT and Gaffield W (editors), Natural and Selected Synthetic Toxins: Biological Implications, 2000 American Chemical Society, Washington D.C. pp: 100-117.) Rightfully, herb advocates argued that the laboratory studies did not apply to the human use of the whole plant – its ethnobotanical and safe use. Yet, as the long arm of the Food and Drug Administration (FDA) sweeps across the alternative health marketplace, the condition of one’s liver and the form of the comfrey are “forgotten,” and our herb choices are slowly being modulated, altered, and eliminated.
In June 1993, then again in a revision in 1996, the American Herbal Products Association adopted a policy that all herbs containing PAs, including comfrey, be labeled as follows: "For external use only. Do not apply to broken or abraded skin. Do not use while nursing." This AHPA policy was later incorporated in its Botanical Safety Handbook. (Herbalgram)
The FDA and Federal Trade Commission (FTC) regularly patrol the alternative health marketplace for products containing comfrey, issuing warnings with restrictive limits. Under the heading of “fraudulent health claims,” the FTC sought an injunction against Christopher Enterprises of Springville, Utah, to stop selling comfrey as a dietary supplement and an ointment for open wounds. Health-food store shoppers can rarely find bulk comfrey since health-food stores are afraid of legal consequences. A major tincture manufacturer now has on its label, “For external use only.” It is the exact formula they had made previously for internal use.
This limit setting does not recognize the availability of PA-free comfrey extracts, which are sold by at least two companies in the U.S. and are available as a raw material in Europe. (Herbalgram)
Instances of Real Harm are Rare
Only a small number of actual cases where severe illness reactions involving the possible use of comfrey have been reported in published studies; there do not seem to be more cases to report.
A 13-year-old boy in England was admitted to a hospital with symptoms that were found to be caused by veno-occlusive disease. He had been suffering from Crohn's disease for three years and had been treated with prednisolone and sulphasalazine, which removed symptoms. At his parents' request, the drugs were discontinued and he was treated with acupuncture and comfrey root prescribed by a naturopath. Exact quantities and frequency are unknown. When admitted to the hospital it appeared that he was again taking prednisolone and sulphasalazine. The authors concluded, "The only possible causal factor in this patient was comfrey." (Dharmananda) Responsible health practitioners can debate the reasons for this child’s illness based on an overload of medications, a faulty diet, and possibly inaccurate acupuncture treatments. What is most significant here is the wholesale blame of the herb comfrey for a complex medical reaction that clearly had been some time in the making.
When I am teaching herbs and nutrition to my college students, I tell them anything can be fatal in large-enough doses. (Case in point: sadly, a college freshman died last year from the rough hazing he got when the frat boys poured 27 gallons of water down his throat in one hour.) There is evidence that too much comfrey on an already toxic liver can be damaging, a skilled herbalist or naturopath ascertains the person’s health history and the state of that person’s liver. No one would tell a man with a broken leg to run in the Olympics; likewise, someone with a compromised liver should not be offered comfrey as a healing aid. And we are smart enough to understand that difference, and we are smart enough to make that choice ourselves, thank you.
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While practicing as a medicinal herbalist for over 30 years, Marguerite Dunne earned a double master's degree in Education and certification in herbology. She has lectured, written articles, made media appearances, and has her own radio program every Monday on WTBQ 1110 AM (WTBQ.com) from 12:30-1:00 p.m. (Eastern Standard Time), The Urban Herbalist. Marguerite is profiled as the featured herbalist in the recently published book, The New Healers (Vista Publications), by Dr. Barbara Stevens Barnum.
References
Hoffman, David, A User’s Guide to Medial Herbalism (Healing Arts Press, 1988).
Wulff-Tilford, Mary L. and Gregory L. Tilford, Herbs for Pets (Bow-Tie Press, 1999).
Duke, Dr. James A., The Green Pharmacy Herbal Handbook (St. Martin’s Press, 2000).
Tenney, Louise, Today’s Herbal Health (Woodland Publishing, 2000).
