Comfrey

Symphytum officinale

Common & Folk Names

• Knitbone
• Boneset
• Bruisewort
• Blackwort
• Slippery Root
• Ass Ear
• Consolida (Latin – “to make whole”)
• Consound
• Healing Herb

Plant Family

Boraginaceae (Borage Family)

Geographic Location

Comfrey is native to Europe and temperate regions of Asia, where it grows wild in damp meadows, along riverbanks, and in ditches. It has been naturalised in North America, New Zealand, and Australia. Today it can be found growing wild or cultivated in most temperate regions worldwide. The related species Russian Comfrey (Symphytum × uplandicum) is a hybrid that is also widely cultivated, particularly varieties bred for low pyrrolizidine alkaloid content.

Habitat

Comfrey thrives in moist, rich soils in damp environments. It naturally occurs along riverbanks, streams, ditches, damp meadows, woodland edges, and waste areas where moisture is consistently available. It prefers partial shade but tolerates full sun if moisture is adequate. Comfrey is often found in disturbed ground and can become weedy in favourable conditions.

Growing Conditions

Sun: Full sun to partial shade. Tolerates a wide range of light conditions but performs best with morning sun and afternoon shade in hot climates.

Soil: Prefers deep, moist, fertile, well-drained soil rich in organic matter. Tolerates a wide pH range (pH 6.0-7.5). Requires consistent moisture but not waterlogged conditions. Comfrey is a dynamic accumulator, with deep taproots (up to 3 metres) that mine minerals from deep in the subsoil and bring them to the surface, making it an excellent companion plant and compost accelerator.

Propagation: Easily propagated by root division or root cuttings in early spring or autumn. Even small pieces of root will regenerate. Can also be grown from seed, though germination is slower and less reliable. Once established, it is nearly impossible to eradicate as any root fragment left in the soil will regrow.

Care: Very low-maintenance once established. Tolerates neglect. Cut back after flowering to encourage fresh foliage growth. Can be harvested multiple times per growing season. Benefits from occasional mulching with compost. Divide clumps every 3-4 years to maintain vigour.

NZ Planting Calendar

Planting: March–May (autumn) or August–October (spring) via root division

Harvest: November–March (summer/autumn) for leaves; May–July (late autumn/winter) for roots

Harvesting Guidelines

Leaves: Harvest throughout the growing season from late spring through autumn, ideally before the plant flowers when allantoin content is highest. Cut leaves with clean scissors or shears, leaving at least one-third of the plant intact to allow regrowth. Young, tender leaves contain less pyrrolizidine alkaloid (PA) content than mature leaves, though all parts contain some PAs. Plants can be cut 3-5 times per season. Best harvested in dry weather. Fresh leaves are preferred for poultices and topical preparations.

Roots: Harvest in autumn after the aerial parts have died back, or in early spring before new growth begins, from second or third-year plants when allantoin content is highest. Roots are best harvested from plants at least 2-3 years old. Dig carefully to extract the entire root system. Wash thoroughly to remove all soil particles. Roots must be chopped or sliced immediately after washing while still pliable, as they become extremely hard when dry. The root contains higher concentrations of both allantoin and pyrrolizidine alkaloids than the leaf.

For storage: Dry leaves and roots in a warm, well-ventilated area away from direct sunlight until completely crisp. Store in airtight containers in a cool, dark place. Dried material loses potency over time; use within one year. Fresh preparations are generally superior to dried.

Parts Used

• Leaf (primary for topical use – lower PA content than root)
• Root (higher allantoin content but also higher PA content)
• Modern products preferentially use the leaf or PA-reduced root extracts

Constituents & their Actions

Allantoin:

This remarkable compound is comfrey’s primary vulnerary constituent and is responsible for its legendary wound-healing reputation. Allantoin comprises 0.6-4.7% of the root dry weight. It is:

• Allantoin (0.6-4.7% in root, 0.3-0.8% in leaf)

The main actions of allantoin are:

• Cell proliferant (stimulates mitosis and cell division)
• Vulnerary (promotes tissue repair and regeneration)
• Keratolytic (promotes removal of dead skin cells)
• Tissue granulation promoter
• Anti-inflammatory
• Moisturising and skin-softening

Pyrrolizidine Alkaloids (PAs) – TOXIC CONSTITUENTS:

These are hepatotoxic (liver-damaging), genotoxic (DNA-damaging), carcinogenic, and mutagenic compounds that severely limit comfrey’s use. The PA content varies significantly depending on plant species, plant part, growing conditions, harvest time, and genetic variation. Some of the main PAs in comfrey are:

• Symphytine (most abundant PA in S. officinale)
• Echimidine
• Intermedine
• Lycopsamine
• Lasiocarpine
• Symlandine
• 7-Acetylintermedine
• 7-Acetyllycopsamine

The main actions (toxic effects) of these PAs are:

• Hepatotoxic (causes veno-occlusive disease/sinusoidal obstruction syndrome)
• Genotoxic (damages DNA)
• Carcinogenic (causes cancer in animal studies)
• Mutagenic (causes mutations)

Mucilage (Polysaccharides):

These complex sugars comprise 10-30% of the fresh root and provide comfrey’s characteristic slimy, demulcent quality. The mucilage consists of:

• Fructose and glucose units
• Complex polysaccharides

The main actions of mucilage are:

• Demulcent (soothes and protects irritated tissues)
• Emollient (softens and moisturises skin)
• Forms protective coating over wounds
• Anti-inflammatory
• Promotes moist wound healing environment

Rosmarinic Acid (Polyphenolic Acid):

A potent antioxidant polyphenol present at 0.5-1.5% in the leaf and root, rosmarinic acid is:

• Rosmarinic acid
• Chlorogenic acid
• Caffeic acid
• α-Hydroxy caffeic acid derivatives

The main actions of rosmarinic acid are:

• Anti-inflammatory (inhibits complement cascade)
• Analgesic (pain-relieving)
• Antioxidant
• Inhibits pro-inflammatory eicosanoid production
• Inhibits lipoxygenase and cyclooxygenase pathways

Tannins:

Condensed tannins provide astringent properties. Some tannins in comfrey include:

• Condensed tannins
• Hydrolysable tannins
• Tannic acid

The main actions of tannins are:

• Astringent (tightens and tones tissue)
• Mild styptic (reduces minor bleeding)
• Antimicrobial
• Wound healing support

Triterpenoids and Other Compounds:

These compounds contribute to comfrey’s anti-inflammatory and healing effects:

• Triterpene saponins
• Sterols
• Vitamin B12 (unusual for a plant source)
• Zinc (important for wound healing)
• Essential amino acids (including asparagine)
• Glycopeptides

The main actions of these compounds are:

• Anti-inflammatory
• Promote granulation tissue formation
• Support collagen synthesis
• Nutritive for tissue repair

Actions with Mechanisms

Vulnerary & Cell Proliferant (Wound Healing):

This is comfrey’s most renowned and clinically validated action. Allantoin is the key driver, directly stimulating the replication and proliferation of fibroblasts, keratinocytes, and other cells essential for tissue regeneration, which in turn accelerates wound healing dramatically. Allantoin promotes granulation tissue formation (the new connective tissue and blood vessels that form on the wound surface), which in turn creates a foundation for epithelisation (the migration of new skin cells across the wound to close it). The mucilage forms a protective, moist layer over the wound, which in turn maintains an optimal healing environment and prevents infection. The combination of cell proliferation, moisture retention, and anti-inflammatory effects makes comfrey extraordinarily effective for promoting rapid healing of cuts, abrasions, bruises, burns, ulcers, and surgical wounds. Topical comfrey preparations have been shown to reduce wound healing time by 30-50% compared to placebo. The effect is so pronounced that the traditional names “Knitbone” and “Boneset” reflect comfrey’s historical reputation for accelerating bone healing by reducing inflammation and supporting soft tissue repair around fractures.

Anti-inflammatory & Analgesic (Pain Relief):

Rosmarinic acid and other polyphenolic compounds provide potent anti-inflammatory effects through multiple mechanisms. They inhibit the complement cascade (part of the immune system that amplifies inflammation), which in turn reduces inflammatory cell recruitment and tissue swelling. They inhibit COX (cyclooxygenase) and LOX (lipoxygenase) enzymes, which in turn blocks the production of pro-inflammatory prostaglandins and leukotrienes responsible for pain, swelling, and redness. The triterpenes stabilise cell membranes and reduce inflammatory mediator release, which in turn further dampens the inflammatory response. The combined effect provides rapid, significant reduction in swelling, pain, and stiffness. Multiple clinical trials demonstrate that topical comfrey is as effective or more effective than topical diclofenac (a pharmaceutical NSAID) for reducing pain and inflammation in ankle sprains, back pain, and osteoarthritis. The analgesic (pain-relieving) effect appears to be both indirect (via anti-inflammatory action) and direct (via interaction with sensory nerve endings). In clinical trials, comfrey cream produced 92% reduction in pain scores compared to 85% for diclofenac, with faster onset of action (significant relief within 1 hour vs. 3-4 hours).

Astringent (Tissue Toning):

The tannins provide mild astringent action, causing proteins in tissue to precipitate and cross-link, which in turn tightens and tones tissue. This helps reduce minor bleeding from abrasions and cuts, which in turn promotes clot formation and wound closure. The astringent effect also reduces excess secretions from weeping wounds and inflammatory exudates, which in turn helps dry and heal damp, weeping skin conditions. This action complements the vulnerary effects and is particularly useful for wounds with excessive discharge.

Demulcent & Emollient (Soothing and Softening):

The high mucilage content provides soothing, cooling relief to inflamed, irritated tissues. The mucilage forms a protective gel-like barrier over irritated skin or mucous membranes, which in turn shields nerve endings from further irritation and provides immediate comfort. It attracts and retains moisture, which in turn keeps tissues hydrated and supports the skin barrier function. This demulcent quality is particularly valuable for burns, sunburn, and inflamed skin conditions. The emollient effect softens and smooths rough, dry, or damaged skin, which in turn improves skin texture and appearance.

Anti-Oedema (Reduces Swelling):

The combined anti-inflammatory effects and the astringent tannins work synergistically to reduce edema (swelling) associated with trauma, sprains, and inflammatory conditions. Clinical studies show comfrey significantly reduces ankle circumference and joint swelling in acute sprains, which in turn restores mobility and function faster than placebo or some pharmaceutical comparators. The reduction in swelling appears to occur via decreased vascular permeability and reduced inflammatory mediator release, which in turn limits fluid accumulation in injured tissues.

Promotes Bone Healing (Historically, Topically for Fractures):

While comfrey cannot heal bones directly when applied topically, its traditional use for fractures (“Knitbone”) reflects its ability to dramatically reduce inflammation, swelling, and pain in the soft tissues surrounding a fracture, which in turn creates optimal conditions for bone healing. By reducing edema and promoting circulation to the injured area, comfrey supports the natural bone healing process. Animal studies have shown that comfrey (when given orally, though this is no longer recommended) increased radiographic bone density around titanium implants, suggesting potential bone-supportive effects. Topically, comfrey poultices were traditionally applied over closed fractures once set to reduce pain and support healing, though this use is now less common with modern fracture management.

Main Use

Primary Clinical Indications (Topical Use Only):

1. Acute Musculoskeletal Injuries:

• Sprains and strains (particularly ankle sprains – most extensively studied)
• Contusions and bruises
• Sports injuries
• Muscle pain (myalgia)
• Ligament injuries
• Tendon injuries

Multiple randomised controlled trials demonstrate that topical comfrey is highly effective for these conditions, often superior to placebo and comparable or superior to pharmaceutical NSAIDs like diclofenac. In a 2004 study of 164 patients with acute ankle sprains, comfrey cream was non-inferior and potentially superior to diclofenac gel, showing better outcomes in pain reduction and functional recovery. The rapid onset of action (significant effects within 1 hour) and excellent safety profile make it ideal for acute injuries.

2. Chronic Pain Conditions:

• Osteoarthritis (particularly knee osteoarthritis)
• Degenerative arthritis
• Chronic back pain (upper and lower)
• Joint pain and stiffness

A landmark 2007 study of 220 patients with knee osteoarthritis found that comfrey root cream (applied 3 times daily for 3 weeks) produced 55% reduction in pain versus 11% in the placebo group, with significant improvements in mobility, function, and quality of life. The effects became more pronounced with duration of treatment. Multiple studies on back pain show 95% reduction in pain intensity with comfrey versus 38% with placebo, with effects noticeable within one hour.

3. Wound Healing (With Important Caveats):

• Minor abrasions and cuts (closed or healing)
• Burns and scalds (first and second degree)
• Slow-healing wounds (superficial)
• Surgical wound healing support
• Ulcers (venous leg ulcers, pressure ulcers)

A 2007 study found that 10% comfrey extract cream accelerated wound healing by 3 days compared to 1% extract cream in patients with fresh abrasions, with complete healing time significantly shorter. The cell-proliferating effects of allantoin make comfrey exceptionally effective for promoting tissue regeneration.

Preparations

Fresh Leaf Poultice (Traditional, Highly Effective): Take 2-3 fresh comfrey leaves, crush or chop to release the mucilaginous juice, and apply directly to the affected area. Cover with a clean cloth or bandage. Leave in place for 20-60 minutes. Can be applied 2-4 times daily. This is the most potent traditional preparation. Use only for acute injuries on intact or minimally broken skin. Rinse off thoroughly after use.

Dried Leaf Poultice: Rehydrate 2-3 tablespoons of dried, crushed comfrey leaf in warm water until soft and pliable. Mash into a paste. Apply to affected area, cover, and leave for 20-60 minutes. Rinse off. Use 2-4 times daily.

Dried Root Poultice: Rehydrate 1-2 tablespoons of dried, chopped comfrey root in warm water until soft. Mash or grind into a paste. Apply to affected area. Note: Root contains higher PA content – use with additional caution and only on intact skin. Limit duration.

Salve/Ointment (Infused Oil with Beeswax): This is the most common and convenient modern preparation. To make: Infuse dried comfrey leaf or root in olive oil or other carrier oil (1:5 ratio, leaf to oil) using the slow heat method (low heat in double boiler for 2-3 hours) or solar infusion (2-4 weeks in warm, sunny location). Strain thoroughly through cheesecloth. Mix the infused oil with beeswax (approximately 1 part beeswax to 4-5 parts infused oil) and pour into tins or jars. Allow to cool and solidify. Apply liberally to affected area 2-4 times daily. Commercial preparations typically contain 10-35% comfrey extract.

Compress (Strong Decoction Soaked Cloth): Simmer 3-4 tablespoons of dried comfrey leaf or root in 2 cups of water for 15-20 minutes. Strain and allow to cool to warm (not hot). Soak a clean cloth in the liquid, wring out excess, and apply to affected area. Cover with plastic wrap or additional cloth to retain moisture. Leave in place for 20-60 minutes. Reapply as needed, 2-3 times daily.

Infused Oil (Base for Salves or Direct Application): Place dried comfrey leaf or root in a jar and cover completely with olive oil, sweet almond oil, or jojoba oil. Allow to infuse for 2-4 weeks in a warm location, shaking daily. Strain through cheesecloth. Use the oil directly on skin or as a base for making salves. Store in dark glass bottles away from heat and light. Use within 6-12 months.

Commercial Cream/Ointment Products: Numerous pharmaceutical-grade comfrey creams are available in Europe, Australia, and New Zealand. These typically contain 10-35% comfrey root or leaf extract standardised for allantoin content and with PAs reduced to detection limit levels. These commercial preparations have been extensively tested in clinical trials and offer the best safety profile. Apply as directed on product label, typically 2-4 grams of cream applied 2-3 times daily.

APPLICATION GUIDELINES:

• Apply to clean, dry skin
• Use sufficient quantity to cover affected area completely
• Massage gently into skin until absorbed
• Can be covered with bandage if needed
• Wash hands after application
• Remove thoroughly after treatment period
• Maximum treatment duration: 4-6 weeks per year (to minimise any theoretical PA exposure)

Dosage

Fresh Poultice: Apply 2-3 times daily for 20-60 minutes. Use for acute injuries. Maximum 2 weeks continuous use.

Salve/Ointment: Apply liberally to affected area 2-4 times daily. Continue as needed for symptom relief. Maximum continuous use: 4-6 weeks, then take a break.

Commercial Cream (10-35% Extract): Apply 2-4 grams (approximately a 6 cm strip or 1-2 teaspoons) to affected area, 2-3 times daily. This dosage has been validated in clinical trials. Maximum duration: As directed, typically 3-8 weeks.

Compress: Apply for 20-60 minutes, 2-3 times daily as needed.

Infused Oil: Apply sufficient amount to cover affected area, 2-3 times daily.

Duration of Use Guidelines:

• Acute injuries (sprains, strains, bruises): Use for 7-14 days or until symptoms resolve
• Chronic conditions (osteoarthritis, back pain): Use for 3-6 weeks, then take a break of at least 4-6 weeks before resuming
• Maximum annual exposure: European guidelines recommend limiting total annual exposure to 4-6 weeks per year to minimise any theoretical PA absorption through skin
• Children: Can be used in children aged 5 years and older following adult dosing guidelines; use only on intact skin

Safety & Drug Interactions

Scientific Evidence

Clinical Efficacy – Topical Use for Musculoskeletal Conditions:

The clinical evidence for topical comfrey is remarkably robust, with multiple well-designed randomised controlled trials demonstrating significant efficacy:

• Ankle Sprains (2004, Koll et al.): Randomised, double-blind, placebo-controlled study of 142 patients with acute ankle sprains. Comfrey ointment (4 times daily for 8 days) produced significantly greater reductions in pain at rest (p<0.0001), pain on movement (p<0.0001), tenderness (2.44 kp/cm² reduction vs. 0.95 kp/cm² with placebo), ankle edema (p=0.0001), and improved ankle mobility (dorsiflexion p=0.002; plantar flexion p=0.0116) compared to placebo. Global efficacy was significantly superior (p<0.0001). No adverse reactions reported. This study was described as “a well-executed and designed RCT with clearly shown beneficial effects.”
• Ankle Sprains vs. Diclofenac (2013, Predel et al.): Single-blind, randomised, parallel-group study of 164 patients with acute ankle sprains comparing comfrey root extract cream to diclofenac gel. Comfrey produced 92% pain reduction versus 85% for diclofenac after 7 days. Comfrey was non-inferior and potentially superior to the pharmaceutical NSAID in all measured variables including pain, swelling, and mobility. Both treatments were well-tolerated with no significant adverse effects.
• Knee Osteoarthritis (2007, Grube et al.): Randomised, double-blind, placebo-controlled trial of 220 patients with painful knee osteoarthritis. Patients applied 2 grams of comfrey root cream (35% extract, equivalent to 17.5g root per 100g) or placebo 3 times daily for 21 days. Results: Pain at rest and during movement decreased by 54.7% in comfrey group vs. 10.7% in placebo group (p<0.0001). WOMAC scores (pain, stiffness, function) reduced by 58.0% with comfrey vs. 14.1% with placebo. Knee mobility and quality of life significantly increased in comfrey group. Effects became more pronounced with duration of treatment. Adverse events: 7 in comfrey group vs. 15 in placebo group. Conclusions: Comfrey root extract is well-suited for treatment of knee osteoarthritis.
• Back Pain (2009, Giannetti et al.): Double-blind, placebo-controlled study of 120 patients with acute upper or lower back pain. Comfrey cream produced 95.2% reduction in pain intensity compared to 37.8% in placebo group, with effects noticeable within 1 hour of first application. Significant improvements in all outcome measurements. Rapid onset of action and sustained benefit throughout treatment period.
• Myalgia/Muscle Pain (2005, Kucera et al.): Randomised, controlled, double-blind study of 215 patients with acute back myalgia. Compared 10% comfrey concentrate cream to 1% reference cream. The 10% comfrey cream produced significantly greater improvement in pain at rest, pain on movement, and pain on palpation compared to the reference cream (p<0.0001). Confirmed known anti-inflammatory and analgesic effects of topical comfrey.
• Wound Healing (2007, Barna et al.): Randomised, controlled, double-blind study of 278 patients with fresh skin abrasions. 10% comfrey extract cream compared to 1% reference cream. After 2-3 days, the 10% cream showed significantly faster reduction in wound area. Complete healing occurred 3 days faster with 10% cream than 1% cream. Study confirmed significant wound-healing effects of comfrey ointment.
• 2013 Systematic Review (Staiger): A critical scoping review evaluated all clinical evidence for external comfrey use and concluded there is robust evidence of benefit for ankle sprains, back pain, abrasion wounds, and osteoarthritis. The review noted that while only one modern RCT exists for each indication, they all consistently point to significant pain-relieving effects in muscle and joint complaints.

Mechanism of Action Studies:

• Allantoin: Well-established in dermatological science as a cell proliferant that stimulates fibroblast replication and promotes collagen synthesis. Allantoin is synthetically produced and widely used in commercial wound-healing and skincare products, validating its efficacy.
• Rosmarinic Acid: Multiple studies confirm potent anti-inflammatory effects via inhibition of complement cascade, COX/LOX enzymes, and pro-inflammatory cytokine production. One study found comfrey’s anti-inflammatory potency equal to or greater than diclofenac in UV-B induced erythema. A positive correlation was found between efficacy and α-Hydroxy caffeic acid concentration in the extract.
• PA Topical Absorption: A 2020 study using Franz diffusion cells with human abdominal skin found only 0.6 ± 0.4% of applied lycopsamine (a comfrey PA) penetrated through skin after 24 hours. Only 5 of 6 diffusion cells showed detectable lycopsamine in skin tissue. This low permeability supports the safety of topical use on intact skin. However, the study authors note that broken skin may have different absorption characteristics.

Pyrrolizidine Alkaloid Toxicity:

• Hepatotoxicity Extensively Documented: Multiple human case reports and animal studies confirm that oral consumption of comfrey causes veno-occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS). PAs are metabolised by liver cytochrome P450 enzymes into reactive pyrrole metabolites that alkylate DNA and damage hepatic endothelial cells, causing vein obstruction and liver failure.
• European Medicines Agency (EMA) Statement (2016): Definitive safety review restricted comfrey to external use only based on extensive toxicology data. Oral use banned due to well-documented hepatotoxicity.
• PA Content Variation (2023, Kimel et al.): LC-MS/MS analysis of Polish comfrey sources found that roots contain significantly more PAs than leaves, with wide variation in PA composition between root samples (up to 20-fold variation) but much more stable PA profiles in leaves. Lycopsamine and its derivatives were found to be more toxic than corresponding stereoisomers (intermedine). Study emphasises need for quality assessment and standardisation of comfrey products for safety.

Comparative Efficacy vs. Pharmaceuticals:

Multiple studies demonstrate comfrey’s efficacy is comparable or superior to pharmaceutical NSAIDs:

• As effective as benzocaine for dental procedures (not comfrey-specific but allantoin)
• Non-inferior and potentially superior to diclofenac for ankle sprains
• Superior to placebo with effect sizes comparable to or exceeding standard pharmaceutical treatments

Western Energetics

Temperature: Cooling. Comfrey reduces the heat of acute inflammation, swelling, redness, and hot, painful injuries. It draws heat out of inflamed tissues and provides cooling relief. Particularly useful for hot, swollen, painful conditions. Contraindicated in cold, deficient conditions without heat/inflammation.

Moisture: Moistening. The high mucilage content and cell-proliferating properties strongly promote moisture and tissue growth. Comfrey supports hydration of damaged tissues and prevents excessive drying. It is ideal for dry, atrophic tissues that need regeneration. Can be too moistening for damp, weeping conditions, though the astringent tannins provide some balance.

Tissue State: Primarily indicated for Atrophy/Dryness (poor tissue repair, slow-healing wounds, tissue deficiency, brittle bones, thin skin, wasting) and Heat/Excitation (acute inflammation, sprains, hot swellings, red, painful injuries). Also useful in Tension/Constriction when there is muscular tension with inflammation. Contraindicated in pure Damp/Stagnation without atrophy or heat components (may increase dampness). The cooling and moistening qualities combined with cell proliferation make it ideal for hot, inflamed tissues that need regeneration.

Taste

Mucilaginous (Slimy): The dominant tactile quality of fresh comfrey leaf and root. This slimy, slippery texture indicates strong demulcent, soothing, and moistening properties. The mucilage coats and protects irritated tissues.

Slightly Sweet: A mild sweet undertone beneath the mucilaginous quality, indicating some nourishing and tonifying properties. The sweet taste relates to building and regenerating tissue.

Bland: The taste is relatively neutral and bland, without strong bitter, sour, or pungent qualities. This mildness reflects its gentle, non-stimulating nature.

Astringent (Secondary): A subtle drying, puckering sensation from the tannins, providing tissue-toning properties. This balances the moistening mucilage somewhat.

Note: Most people find the taste and texture unpleasant, which is fortunate given that internal use is contraindicated. The plant’s taste is memorable primarily for its slimy, mucilaginous quality.

Plant Lore

The name “Comfrey” derives from the Latin conferva (“to grow together”) and Symphytum from the Greek symphyo (“to unite”). These names directly reference the plant’s ancient reputation for healing bones and “knitting” broken parts back together. The common names “Knitbone” and “Boneset” reflect the same belief – that comfrey poultices could heal fractured bones so perfectly that the repair was said to be stronger than the original bone.

Comfrey has been used medicinally for over 2,000 years. The ancient Greek physician Dioscorides (40-90 CE) wrote in his Materia Medica: “The roots are black on the outside and white and slimy on the inside. Finely ground and then drunk they are beneficial for those spitting blood and those suffering from internal abscesses.” While this internal use is no longer recommended, it demonstrates comfrey’s ancient reputation as a powerful healer.

Pliny the Elder (23-79 CE) documented in his Naturalis Historia that comfrey was used for bruises and sprains, and that syrups or decoctions of comfrey ensure rapid healing of wounds. These uses – documented nearly 2,000 years ago – remain comfrey’s primary applications today (though now applied topically rather than internally).

The medieval physician Paracelsus (1493-1541) used comfrey extensively in his practice, particularly for bone injuries. Comfrey was a staple in monastery gardens throughout medieval Europe, where monks cultivated it for treating wounds and injuries among pilgrims and travelers.

The herbalist Nicholas Culpeper (1616-1654) wrote in his Complete Herbal (1653): “The roots of Comfrey taken fresh, beaten small, spread upon leather, and laid upon any place troubled with the gout, doth presently give ease of the pains; and applied in the same manner, giveth ease to pained joints, and profiteth very much for running and moist ulcers, gangrenes, mortifications, and the like.”

In Traditional Chinese Medicine, comfrey is known as Xuanma and has been used to promote wound healing, reduce inflammation, and alleviate pain, though it is not a primary herb in the Chinese materia medica.

Folklore held that a comfrey poultice applied to a broken bone could knit it so tightly that the bone would be stronger after healing than before the break. This reputation, while exaggerated, reflects the dramatic reduction in pain and swelling that topical comfrey provides, which creates optimal conditions for natural bone healing.

There is a darker side to comfrey’s history: its widespread internal use in the 20th century as a “health tonic” led to multiple cases of severe liver disease and death before the hepatotoxicity of pyrrolizidine alkaloids was fully understood. This tragic history underscores the importance of evidence-based herbalism and the need to balance traditional use with modern toxicology. Comfrey serves as a cautionary tale – even plants with genuine healing properties can be dangerous when used inappropriately.

Additional Information

The Healing Paradox:

Comfrey represents one of the most interesting dilemmas in herbalism – it is simultaneously one of the most effective wound-healing and pain-relieving herbs known to science, AND one of the most toxic when used internally. This paradox means comfrey must be used with great care and respect. Modern herbalists must balance honoring traditional knowledge with protecting patient safety. The resolution is clear: topical use only, on intact or minimally broken skin, for limited durations.

Dynamic Accumulator & Companion Plant:

Beyond its medicinal uses, comfrey is renowned as a dynamic accumulator – a plant whose deep taproot (up to 3 metres) mines minerals from deep in the subsoil and brings them to the surface. When comfrey leaves decompose, these minerals become available to other plants. This makes comfrey an exceptional:

• Compost accelerator (high nitrogen content speeds decomposition)
• Liquid fertiliser (“comfrey tea” made from rotted leaves is nutrient-rich)
• Mulch (nutrient-rich leaves suppress weeds and feed soil)
• Companion plant (benefits neighboring plants)

Organic gardeners and permaculturists treasure comfrey as much for these properties as for its medicine. The same plant that heals human tissues also heals and feeds the soil.

PA-Free Cultivars:

The development of PA-free or PA-reduced comfrey cultivars represents an important advancement. Symphytum × uplandicum ‘Bocking 14’ (a Russian Comfrey hybrid) has been bred to contain virtually undetectable levels of pyrrolizidine alkaloids while maintaining high allantoin content. This cultivar is the safest choice for those growing comfrey for topical preparations. Several pharmaceutical companies have also developed proprietary PA-reduced extraction methods that concentrate therapeutic compounds while removing or minimising PAs.

Do Not Confuse With:

Comfrey should not be confused with Common Boneset (Eupatorium perfoliatum), which is a completely different plant in the Asteraceae family. Both share the common name “Boneset” but are botanically unrelated and have different uses and safety profiles.

Storage & Shelf Life:

• Fresh leaves: Use immediately for poultices; do not store (wilt quickly)
• Dried leaves: Store in airtight containers away from light and moisture; use within 1 year
• Dried roots: Store in airtight containers; use within 1 year (becomes very hard when dry)
• Salves: Store in cool, dark place; typically stable for 1-2 years
• Infused oils: Store in dark glass bottles; use within 6-12 months
• Commercial creams: Follow manufacturer expiration dates; typically 2-3 years unopened

New Zealand Availability & Pricing:

Comfrey grows readily in New Zealand’s temperate climate and is widely naturalised. It can be considered weedy in favourable conditions.

• Growing Your Own: The most economical option. Plants readily available from garden centres, herbal suppliers, and other gardeners (often free, as comfrey spreads vigourously). Once established, provides unlimited supply. ‘Bocking 14’ cultivar recommended for lowest PA content.
• Dried Herb: Available from herbal suppliers in various sizes. Dried leaf and dried root both available.
• Commercial Creams: Available from pharmacies, health food stores, and online. Prices vary widely depending on formulation and source. Look for products standardised for allantoin content with PA content stated as below detection limits.
• Infused Oils & Salves: Available from artisan herbalists and natural product makers in various sizes.

Regulatory Status in New Zealand:

Topical comfrey products are permitted in New Zealand for external use only. Internal use products are not permitted for sale. Medsafe (New Zealand Medicines and Medical Devices Safety Authority) regulates comfrey-containing products as medicines when therapeutic claims are made.

Making Safe Home Preparations:

For those making comfrey preparations at home:

1. Prefer leaves over roots (lower PA content)
2. Harvest young leaves (lower PA content than mature leaves)
3. Use dried rather than fresh for infusions (some PAs are water-soluble; oil infusions are safer)
4. Limit use duration (4-6 weeks per year maximum)
5. Use only on intact or minimally broken skin
6. Consider growing ‘Bocking 14’ cultivar (virtually PA-free)
7. Store preparations properly and use within shelf life

Sources

Koll, R., Buhr, M., Dieter, R., Pabst, H., Predel, H. G., Petrowicz, O., et al. (2004). Efficacy and tolerance of a comfrey root extract (Extr. Rad. Symphyti) in the treatment of ankle distortions: Results of a multicenter, randomized, placebo-controlled, double-blind study. Phytomedicine, 11(6-7), 470-477. https://doi.org/10.1016/j.phymed.2004.02.001

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