Topical Comfrey Helps Sprained Ankles

Townsend Letter for Doctors and Patients,  Jan, 2001  by Kerry Bone

• E-mail
• Print
• Link

In Germany, a double-blind, multicenter, randomized, placebo-controlled trial on 142 patients suffering from unilateral acute ankle sprains (mean age 31.8 years, 78.9% male) conclusively demonstrated the efficacy of a comfrey root extract ointment. [1] Treatment consisted of 4 applications per day for 8 days. Compared to placebo, comfrey treatment was superior in terms of pain reduction (tonometric measurement, p[less than]0.0001) and ankle edema (figure of eight method, p=0.000l). In relative terms pain was reduced by 63% for the active treatment after 8 days (vs 25% for placebo) and edema by 61% (vs 36% for placebo). Statistically significant differences between active treatment and placebo could also be demonstrated for ankle mobility and global efficacy. In terms of the latter, 81% of patients rated comfrey treatment as good or very good (vs 50% for placebo, p[less than]0.0009) and 86% of physicians rated comfrey as good or very good (vs 23% for placebo, p[less than]0.0001). No side effects were reported.

Commentary

Comfrey contains potentially toxic unsaturated pyrrolizidine alkaloids (PA). In Germany the maximum allowed PA dosage from topical application is 100 [micro]g per day and treatment is limited to 4 to 6 weeks per year (for doses between 10 and 100 [micro]g per day). However these restrictions are not relevant to the test medication used in the trial which contained only 0.35 [micro]g/g of PA, resulting in a daily dose of PA well under 10 [micro]g.

The authors attributed their striking findings to the anti-inflammatory, antioxidant, antiexudative and healing properties of allantoin and rosmarinic acid, which are key components of comfrey. While this is certainly the case for effects of comfrey on the skin, with our current knowledge it is difficult to explain the deeper healing effect observed in the trial.

It is certainly true that there is a reasonable body of evidence for the anti-inflammatory and healing effects of comfrey on various skin conditions. A key component here is the allantoin which has been used for over 70 years as an 'effective' and 'non-irritating' skin moisturizer in cosmetics and toiletries. It acts on the non-keratin soluble cement matrix, binding the cornified cells of the horny layer of the skin and thus promoting the water binding ability or hydroscopicity of the layer. Allantoin also acts directly on keratin molecules causing them to hold more water. This application would benefit disease states such as psoriasis.

Allantoin acts to reduce or remove callus and other forms of hyperkeratinization by its action in dissolving the cement holding the cornified cells together. [2] Specific research findings are:

* Allantoin applied locally is useful in the treatment of skin ulcers, burns, scalds and fistulas. Allantoin stimulated epithelial regrowth, effectively removed necrotic tissue and stimulated leukocytosis. [3]

* Local application was observed to accelerate the healing of wounds and ulcers by stimulating the formation of granulation tissue. [4-7] Allantoin stimulated abundant growth of healthy granulation tissue in slowly healing suppurative wounds. [8]

* In concentrations of 0.01-0.2% it was keratolytic, promoted epithelization and wound healing and also had anti-inflammatory activity. [9]

* In vitro tests confirm the protein-dispersing activity of allantoin as measured by the concentration of reactive sulphhydryl groups released from the protein of skin samples. Keratolytic activity on psoriatic scales was demonstrated in vitro by incubation with 0.2% allantoin solution. Keratolysis is a process in which horny cells are dispersed with a release of non-keratinous material (such as free amino acids and acid mucopolysaccharides), which contributes to the appearance and physiological properties of the horny layer. [10-12] Using the same experimental model, 0.6% allantoin solution was found to release more free amino acids and acid mucopolysaccharides from normal horny layers than control solutions. [12]

* The wound healing activity of allantoin may be mediated via hyaluronic acid. [9]

There is also some evidence for the beneficial skin effects of comfrey. Comfrey has been used for hundreds of years traditionally to heal wounds and mend bones. During World War I it was found that serious wounds healed quickly when treated with comfrey. Later, allantoin was isolated as an active ingredient responsible for the healing. [13] (In early research wounds infested by blowfly maggots were observed to heal more rapidly than those without. The maggots were found to be excreting allantoin.) [8,14]

An ointment containing comfrey extract with reduced pyrrolizidine alkaloid content demonstrated an anti-inflammatory effect (as measured by decreased redness and pain sensitivity of UV-B irradiation) on human skin. [15]

In an open study, over 300 patients with various dermatological complaints were treated with comfrey products over 12 months. [12] The comfrey products included comfrey ointment (alcoholic extract of comfrey leaf and root in ointment base), comfrey salve (comfrey leaf in salve base), comfrey tincture (alcoholic extract of leaf) and comfrey compress (aqueous poultice of comfrey leaf or root). The best results were obtained for conditions that required improved circulation and local stimulation.