Wise Mind Herbs

The information on this page has been prepared with reference to published scientific literature, not by a medically qualified expert. It is not medical advice. Any decision to use a supplement or herb-based product is your responsibility. Consult a suitably qualified medical professional, especially if you have underlying conditions. Remember, nothing is for everyone, and not everything sold is what it claims to be. Some things work for some people, some of the time.

Comfrey - Symphytum officinale

Comfrey is a perennial herb belonging to the family Boraginaceae. The most commonly used species in herbal medicine is Symphytum officinale (common comfrey), though Symphytum asperum (prickly comfrey) and Symphytum x uplandicum (Russian comfrey, a hybrid of S. officinale and S. asperum) are also utilized. Other common names include knitbone, boneset, bruisewort, and healing herb, reflecting its traditional use in treating bone and tissue injuries. Plants sometimes confused with comfrey but botanically distinct include Tussilago farfara (coltsfoot) and various Borago species (borage).

Active Constituents

Comfrey contains several bioactive compounds, including allantoin (0.5-1.7%), rosmarinic acid (up to 6%), mucilage (29%), tannins, and most notably, pyrrolizidine alkaloids (PAs) such as symphytine, lycopsamine, and intermedine. The PAs are the source of significant safety concerns associated with comfrey use. Research has focused primarily on allantoin and rosmarinic acid for their potential therapeutic effects, while seeking to minimize PA content.

Therapeutic Applications with Scientific Support

Contrary to traditional claims of comfrey "curing" conditions, scientific evidence supports more limited applications, primarily for topical use:

• Acute back pain: Randomized controlled trials show efficacy of topical comfrey preparations in reducing pain intensity
• Osteoarthritis: Moderate evidence for pain reduction and improved mobility in knee and ankle osteoarthritis
• Sprains and strains: Several studies demonstrate accelerated healing and pain reduction in ankle sprains and muscle injuries
• Wounds and contusions: Limited evidence for improved healing of minor skin wounds and bruises
• Inflammation: In vitro and animal studies show anti-inflammatory properties, primarily attributed to rosmarinic acid

Dosages and Standardization

For topical applications, clinically studied preparations typically contain:

• 5-20% comfrey root extract, standardized to 0.2-1% allantoin
• Creams/ointments containing 10% comfrey extract with 0.2% diethylamine salicylate for pain relief
• Products standardized to contain less than 0.35 μg pyrrolizidine alkaloids per day as recommended by German Commission E

Application frequency in clinical studies ranges from 2-4 times daily for up to 4-6 weeks. There is no standardized effective dosage for internal use, as oral consumption is strongly discouraged due to safety concerns.

Side Effects and Safety Concerns

The safety profile of comfrey is dominated by concerns regarding pyrrolizidine alkaloids:

• Hepatotoxicity: PAs are hepatotoxic and can cause veno-occlusive disease (hepatic sinusoidal obstruction syndrome)
• Carcinogenicity: PAs have demonstrated carcinogenic and genotoxic properties in animal studies
• Cumulative toxicity: PAs accumulate in the body over time, potentially causing delayed-onset liver damage
• Topical absorption risks: While significantly lower than oral consumption, some studies suggest limited systemic absorption of PAs through skin application
• Pregnancy/lactation: Contraindicated due to potential developmental toxicity
• Drug interactions: May interact with hepatotoxic medications, enhancing liver damage risk

Regulatory Status and Restrictions

Due to safety concerns, regulatory authorities in multiple countries have placed restrictions on comfrey:

• FDA (USA): Prohibits internal use products; issues warnings against oral consumption
• EMA (Europe): Recommends limiting PA content in topical preparations and duration of use
• German Commission E: Permits external use only, with PA limitations
• Australia/TGA: Prohibits internal use and restricts external use to specific formulations

Research on High-Dose Applications

There is a significant knowledge gap regarding high-dose applications of comfrey. Ethical concerns regarding PA toxicity have prevented dose-escalation studies in humans. Animal studies examining doses above therapeutic range consistently show increased hepatotoxicity rather than enhanced benefits. No clear maximum efficacious dose has been established for topical preparations, and researchers have focused instead on minimizing PA content while maintaining therapeutic effects of other compounds. This represents a significant research gap in understanding the full dose-response relationship.

Commercial Pharmaceutical Products

Several pharmaceutical-grade products containing comfrey extracts are commercially available, primarily in European markets:

• Kytta-Salbe®: Contains PA-depleted comfrey root extract, marketed for sprains, strains, and contusions
• Traumaplant®: Contains extract from aerial parts of S. x uplandicum, used for contusions and muscle pain
• Beinwell-Salbe®: Topical comfrey preparation for joint and muscle pain
• Symphytum Comp.®: Homeopathic preparation containing Symphytum

These products typically use specialized extraction techniques to minimize PA content while preserving other active compounds, particularly allantoin and rosmarinic acid.

Conclusion

Scientific evidence supports limited therapeutic applications for comfrey, primarily as a topical agent for musculoskeletal conditions and minor wounds. However, significant safety concerns persist regarding pyrrolizidine alkaloid content. The therapeutic window appears narrow, with potential benefits outweighed by risks in many contexts, particularly for internal use. Modern pharmaceutical preparations focus on PA-depleted extracts to minimize risk while maintaining efficacy. Future research should explore safer analogues of active compounds and improved extraction methods to address the benefit-risk balance.

References

Steinhoff, B. (2019). Pyrrolizidine alkaloid contamination in herbal medicinal products: Limits and occurrence. Food and Chemical Toxicology, 130, 262-266.

Frost, R., O'Meara, S., & MacPherson, H. (2014). The external use of comfrey: A practitioner survey. Complementary therapies in clinical practice, 20(4), 347-355.

Kucera, M., Barna, M., Horácek, O., Kálal, J., Kucera, A., & Hladíkova, M. (2005). Topical symphytum herb concentrate cream against myalgia: a randomized controlled double-blind clinical study. Advances in therapy, 22, 681-692.

Oberlies, N. H., Kim, N. C., Brine, D. R., Collins, B. J., Handy, R. W., Sparacino, C. M., ... & Wall, M. E. (2004). Analysis of herbal teas made from the leaves of comfrey (Symphytum officinale): reduction of N-oxides results in order of magnitude increases in the measurable concentration of pyrrolizidine alkaloids. Public Health Nutrition, 7(7), 919-924.

Salehi, B., Sharopov, F., Boyunegmez Tumer, T., Ozleyen, A., Rodríguez-Pérez, C., M Ezzat, S., ... & Martins, N. (2019). Symphytum species: a comprehensive review on chemical composition, food applications and phytopharmacology. Molecules, 24(12), 2272.

Smith, D. B., & Jacobson, B. H. (2011). Effect of a blend of comfrey root extract (Symphytum officinale L.) and tannic acid creams in the treatment of osteoarthritis of the knee: randomized, placebo-controlled, double-blind, multiclinical trials. Journal of Chiropractic Medicine, 10(3), 147-156.

Staiger, C. (2012). Comfrey root: from tradition to modern clinical trials. Wiener Medizinische Wochenschrift (1946), 163(3), 58.

Trifan, A., Wolfram, E., Skalicka-Woźniak, K., & Luca, S. V. (2024). S ymphytum genus—from traditional medicine to modern uses: an update on phytochemistry, pharmacological activity, and safety. Phytochemistry Reviews, 1-58.

Weston, C. F., Cooper, B. T., Davies, J. D., & Levine, D. F. (1987). Veno-occlusive disease of the liver secondary to ingestion of comfrey. British Medical Journal (Clinical research ed.), 295(6591), 183.