The World Health Organization estimates that 80% of people around the world use herbal medicine (Null & Gale, 2018). In fact, most of us turn to herbal options before opting for conventional drugs.
Despite these trends, herbal and alternative healing options are quickly reported when someone has an adverse effect. Comfrey, Symphytum officinale, is one of these herbs, despite its great benefits to our health.
The name comfrey comes from the Latin word “confirma,” which means to heal or to unite. It can be used as an anti-inflammatory, antiseptic, astringent, demulcent, emollient, diuretic, expectorant, laxative, and tonic (Petersen, 2014).
To find out what these terms mean, look at these articles:
It also can cause harm when it is over-consumed or over-used and should thus be used with caution. Believe it or not, this is the case with most things we consume. Take alcohol for example. It is readily available, but if we over-consume it, it can have dire negative consequences on our health. That is why proper use is cautioned for alcohol and other such substances.
Natural medicines are not given the same treatment. In fact, natural medicines are often vilified to make us wary of them and to instead lead us to commercially available medical options. This is what has happened with comfrey.
Please read this article in its entirety to make sure you understand the full effects of using comfrey.
Beneficial Effects of Comfrey
Comfrey can be used externally, particularly as a poultice, to treat abscesses, bedsore, boils, bruises, burns, hemorrhoids, inflammation, sprains, and swelling (Petersen, 2014).
It can be used as a tea to alleviate asthma, bleeding, bronchitis, coughs, constipation, diarrhea, fractures, and whooping cough (Petersen, 2014).
It can also be used in a gargle to treat laryngitis and tonsillitis. A decoction of the root is the best form of treatment. You can read about how to prepare poultices, teas, and decoctions here.
Studies have shown that ointment made from comfrey root extract is more effective than over-the-counter pain relieving and anti-inflammatory medical ointments (Predel, Giannetti, Koll, Bulitta, & Staiger, 2005).
Beneficial Components of Comfrey
The roots of comfrey contain the beneficial components or constituents of the plant. Comfrey leaves also have active constituents, however, some of the most therapeutic ones, such as mucilage and allantoin, are found in higher concentration in the roots.
Comfrey root has high amounts of allantoin, which helps in tissue repair and stimulates tissue growth; carotene, which is precursor to Vitamin A; mucilage, which is a useful and active demulcent; rosmarinic acid, which is an active expectorant, antioxidant, anti-inflammatory and antimicrobial; tannin, which is antiseptic and astringent; pyrollic ester, a mild antimuscarinic; and pyrrolizidine alkaloid (PA), which is the most controversial (Petersen, 2014).
The controversy is based on evidence that a species related to comfrey, namely Symphyti radix, which contains a high amount of PAs, was found to cause liver failure or liver damage, as well as carcinogenic or mutagenic action (Wichtl, 2004). These concerns arose from reports from people who over-consumed the herb internally, as well as from testing the herb on animals, such as bacteria and fruit flies (Dharmananda, 2001). As a result, the FDA has limited all types of comfreys to external use only.
How to Use Comfrey
Given the controversy surrounding PAs in comfrey, the herb is contraindicated to be consumed internally. Some herbalists may still recommend consumption of the herb, but in small dosages and not over long periods of time. Preparing the herb with heat, as a tea or hot infusion, seems to inactivate the PAs and make it safe for consumption.
Even for external use, the herb should not be placed on open wounds. Since allantoin stimulates tissue growth, there is a danger that in an infected open wound tissue would grow around the infection without healing it and thus, push the infection internally.
It also should not be applied topically for more than four to six weeks, particularly if used daily.
The safest application is through a poultice, given that PAs are not absorbed through the skin. It should also not be consumed internally. Pregnant or nursing women should not use it at all, even applied externally.
An additional precaution is to ensure properly identifying the herb. Comfrey has been confused with other more toxic Symphytum species. When using comfrey, make sure it is listed as Symphytum officinale.
My Take on the Concern Over Comfrey
In evidence-based medicine, a valid cause and effect relationship between two variables requires a clinical study with a randomized, placebo-controlled trial (Portney & Watkins, 2009). The studies that led to the contraindications on the use of comfrey are not only from a species related to comfrey and not from comfrey itself but are also based on reports from four individuals. I don't believe this constitutes as enough evidence to meet the criteria to prove that comfrey causes deleterious effects on humans.
In contrast, people have more severe adverse effects from modern medical drugs. In 2014, prescription drugs caused 1.6 million injuries and 770,000 hospital stays. In 2016, prescription overdoses caused over 64,000 deaths, and in 2017 opioids caused over 42,000 deaths (Null & Gale, 2018). In many of these incidences, drugs were used as indicated, and still caused adverse effects. Yet, the FDA doesn’t limit the use of these drugs.
In addition, the studies conducted on animals also do not provide enough evidence for caution against the use of comfrey in humans. Weiss & Fintelmann (2000) warn that most animal experiments involve testing herbal drugs at dosages that are different from therapeutic dosages in humans. In addition, animals are usually administered the herb in unnatural conditions, which could also contribute to their adverse reaction. Lastly, humans have completely different constitutions to animals and the effect of something on an animal cannot be equally compared to its effect on humans. I am certain that the comparison between humans and bacteria or fruit flies is even more far-fetched.
Despite the concerns raised, given that there is no direct evidence of comfrey’s damage to humans, I believe the FDA should not be as concerned with internal use of comfrey, but instead be concerned with creating careful guidelines under which the herb can be consumed, ensuring the clear labeling of contraindications, interaction with other drugs, maximum daily dosage, and frequency of use.
Dharmananda, S. (2001). Safety Issues Affecting Herbs: Phyrrolizidine Alkaloids. Institute for Traditional Medicine. Retrieved from http://www.itmonline.org/arts/pas.htm
Null, G. & Gale, R. (2018). Chinese botanical medicine: Wikipedia claims it is fake, we are certain it is real. GreenMedinfo. Retrieved on September 6, 2018 from http://www.greenmedinfo.com/blog/chinese-botanical-medicine-wikipedia-claims-it-fake-we-are-certain-it-real
Petersen, D. (2014). HERB 502 Advanced Herbal Materia Medica I. Portland, OR: American College of Healthcare Sciences.
Portney, L. G. & Watkins, M. P. (2009). Foundations of Clinical Research: Applications to Practice. (3rd ed.). Upper Saddle River, NJ: Pearson Prentice Hall.
Predel, H. G., Giannetti, B., Koll, R., Bulitta, M., & Staiger, C. (2005). Topical comfrey root is superior to diclofenac (NSAID) gel in the treatment of ankle distortions.Phytomedicine, 12(10), 707-714.
Ulbricht, C. E. (2010). Natural Standard: Herb & Supplement Guide- An Evidence-Based Reference. St. Louis, MO: Elsevier Mosby.
Weiss, R. F. & Fintelmann, V. (2000). Herbal Medicine, 2nded. Stuttgart, Germany: Georg Thieme Verlag.
Wichtl, M. (Ed.). (2004).Herbal Drugs and Phytopharmaceuticals: A Handbook for the Practice on a Scientific Basis, 3rd ed. Boca Raton, FL: CRC Press.