Other names: Slippery root, Knitbone, Boneset, Black Root, Blackwort
Comfrey is part of the borage family of plants, originating from Europe. With a history of traditional use stretching back thousands of years, the herb has been cultivated for traditional medicinal use. The leaf, root and root-like stem (known as the rhizome), are used in herbal medicine. From the 17th century it is documented that comfrey is used for internal and external wounds. The British Herbal Pharmacopeia provides more specific understandings of pathology; suggested applications include for gastric and duodenal ulcers and colitis, as well as skin ulcers and wounds. Other common modern uses include oral intake for conditions such as heavy menstrual periods, diarrhoea, bronchitis and chest pain associated with angina. It is also used as a gargle for gum disease, and may also be used for sore throats, however more robust scientific evidence is needed to support these claims. Other applications include topical use for conditions such as muscle soreness, bruising, rheumatoid arthritis, varicose veins, gout and fractures.
Mechanisms of Action:
In 1912, Macalister reported the presence of a major component in comfrey, allantoin and its promoting effect on cell proliferation (cell reproduction supporting the management of healthy tissues in the body by speeding up the process of new tissue growth) [i]. Allantoin is known to be present in foetal development, the placenta contains this compound as the baby grows. This compound is also present in breast milk to support growth after birth [ii].
Benefits of Comfrey:
Joint Pain and Relief of Pain from Injury:
Comfrey has also been used historically for many varieties of injuries and accidents, including but not limited to broken bones. The traditional name of Knitbone, given to comfrey, alludes to the traditional reports of its healing properties in muscle sprains, brushing, burns and joint inflammation.
A research article, including analysis of individual clinical trials, showed evidence of benefit for conditions such as ankle distortion, back pain and osteoarthritis [iii].
One particular study was a randomised, controlled clinical trial. It demonstrated an improvement of symptoms such as acute back pain and restriction of movement with use of comfy root extract cream including methyl nicotinate [iv]. Moreover, authors of a trial concluded comfrey extract may be superior to Diclofenac gel (a Non-Steroidal-Anti-Inflammatory conventional medical application) in treating sprained ankles [v]. Similarly, comfrey was said to show promise in treating pain after minor dental surgery [vi].
Comfrey also contains vitamins and minerals such as vitamin C, B vitamins, cell protective antioxidants and minerals such as calcium and magnesium to support healthy bones and tissues [vii]
Health of the Skin:
The aforementioned compound contained in comfrey, allantoin, has been used in the treatment of skin ulcers and skin scarring. A study highlighted the improvement in skin elasticity from application of allantoin. This compound was also said to have hydrating and moisturising effects on skin [viii]. Evidence from the journal Complementary Therapies in Medicine supports use of comfrey topical ointment for its beneficial effects on abrasion wounds as well as venous leg ulcers.
Naturally occurring allantoin as found in Comfrey [ix] may reduce abnormal thickening of the skin caused by a condition known as hyperkeratinisation; denoting to excess production of keratin and the subsequent compromised structure of the barrier function [x].
Allantoin interacts with the skin’s keratin to thin out an abnormal, thick stratum corneum, and this is the reason that allantoin is known for leaving skin feeling smooth [xi].
Pregnancy and Breastfeeding: Comfrey is not safe to take by mouth or applied to the skin if you are pregnant or breastfeeding. The active components in comfrey might cause birth defects, these components can also be absorbed through the skin.
Liver disease: There is a concern that comfrey might make liver disease worse. Do not use comfrey in cases of liver disease.
Medications that have actions on the liver:
Taking comfrey along with medication that might harm the liver can increase the risk of liver damage. Do not take comfrey if you are taking a medication that can harm the liver. There are many drugs which may have negative actions on the liver, please consult with your prescribing doctor prior to taking comfrey.
Medications that increase break down of other medications by the liver:
Cytochrome P450 3A4 (CYP3A4) inducers interact with comfrey. Comfrey is broken down by the liver. Some substances which form when the liver breaks down comfrey can be harmful to the body. Medications that cause the liver to break down comfrey might increase the toxic effects of chemicals contained in comfrey. Please consult with your prescribing doctor prior to taking comfrey.
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