Sometimes called knitbone or All Heal, comfrey (Symphytum officinale L.) has been used for centuries to support bone, wound and lung healing, and at one time was recommended as a tea to soothe digestive issues. These days it’s also often recommended for:
- Soothing sprains, bruises, swelling, minor shallow-cut skin injuries and burns
- Easing tight muscles
- Boosting softness and shine when used as a hair rinse
- Moisturizing skin, which is why it’s incorporated into many skin serums and creams
Comfrey is rich in a compound called allantoin, which supports cell formation and granulation, also known as the creation of new tissue and microscopic blood vessels during the healing process.
Is comfrey safe?
Although it has been traditionally used both externally and internally, recent documentation of serious liver damage from drinking comfrey tea has prompted many herbalists to stop recommending the internal use of comfrey. External use of comfrey is still considered safe, though, so comfrey shouldn’t be thrown out of your herbal toolkit altogether.
The problem with comfrey is that every plant contains varying levels of several kinds of pyrrolizidine alkaloids, or PAs. PAs cause veno-occlusive liver disease in some people, a condition where the breakdown of the PAs release pyrroles that damage the veins in the liver that eventually leads to scarring and clogging (1).
This isn’t based on some petri dish or lab-rat study…these are real people and veno-occlusive liver disease can – and has been – fatal. However, those are individual occurrences, and no human clinical trials can be done to test the safety of comfrey due to the potential risks. (2)
In addition, some herbalists argue that the risks have not been properly assessed because there are several kinds of comfrey – common comfrey (S. officianale), prickly comfrey (Symphytum asperum) and Russian comfrey (S. uplandicum) – and it’s unclear which one was consumed in the cases that reported negative effects. Certain cultivars are thought to be lower in PAs than others, but more research is needed to confirm that.
The chances of someone getting liver occlusion from PA ingestion can’t be predicted. Liver occlusion is more likely to occur in people with compromised livers or people with malnourishment, but it can occur in anyone, any age, any time. On the other hand, some people can ingest comfrey and never get an occluded liver.
The entire comfrey family contains PAs, including the common garden companion borage. PAs are in the largest amounts in the root, and lowest in the oldest leaves. Other medicinal plants with PAs are the lung-remedy coltsfoot, and the recently discovered presence in immune supporting boneset (Eupatorium perfoliatum). The aster, pea, and orchid families also contain PAs (over 6,000 plants).
This debate is compounded by the fact that not all PAs are dangerous. Of the 650+ PAs currently known, non-toxic PAs are found in Echinacea and other medicinal aster family species. Coltsfoot (an antitussive herb) PAs are rumored toxic, but many attribute this to mistaken identification of a known toxic look alike, Petasites, and not coltsfoot. Coltsfoot PAs are mostly the non-toxic kind, but it does have extremely small amounts of the known hepatotoxic PAs. (1) Some herbalists will use coltsfoot long term; some will use it short term; some won’t use it with pregnant women/children; some won’t use it at all.
Should I drink comfrey tea?
The Botanical Safety Handbook, 2nd Edition, lists comfrey as Class 2a, 2b, and 2c: which means that it is recommended for external use only, and not for use in pregnancy or nursing. Comfrey is not recommended for use with deep wounds or unset bones.
Alternatives to comfrey tea for internal use
Comfrey was historically recommended internally to support healing when there is a dry cough or connective tissue injury (bone and skin). Fortunately, there are alternative herbs for both of these situations that don’t pose the same risk as comfrey.
Mullein leaf and marshmallow root can be taken together as a moistening, healing, lung-supportive remedy when a dry cough is present. To make a simple tea, pour 1/2 ounce of each into a jar and steep in 1 quart of lukewarm/cold water for 4-8 hours, then strain and drink.
For bone or other connective tissue injuries, consuming foods that provide nutrients for healing can go a long way. Bone broth, ample protein, healthy fats, foods and herbs high in B-vitamins, vitamin C, vitamin E, bioflavonoids, and minerals can be consumed during an injury, as well as getting adequate sun exposure for Vitamin D along with the benefits of infrared light. Comfrey can be used externally to support healing as well.
How to use comfrey externally
Although ingesting comfrey is not recommended, using comfrey externally is considered safe and can be very helpful for supporting the healing process with breaks, sprains, and strains, as well as minor shallow-cut skin injuries and burns. (3) It’s even been shown to ease tight muscles and support a healthy inflammatory process. (4)(5) Comfrey roots are the most powerful, followed by young leaves, with older leaves considered the least powerful.
Some people do get a skin rash reaction from comfrey leaves, so be careful during your first time handling them or using remedies made from comfrey leaves.
Both the leaves and roots can be used to make external comfrey remedies, often in either an oil, salve, or plaster. It’s best to use these acutely, no more than 4-6 weeks at a time, to avoid toxicity issues for any comfrey that gets into the blood stream through the skin (although chemically speaking PAs have very low solubility in oils, so comfrey oils and salves should be low in PAs.) (1)
Where to buy comfrey oil and salve
Below you’ll find recipes for making comfrey oil and salve at home, but if you don’t want to DIY here are some good pre-made options:
How to make comfrey oil
The most common way of using comfrey externally for connective tissue injuries or small wound healing is through comfrey-infused oils.
- Organic dried comfrey leaves or comfrey roots
- Olive oil (Or another oil that you prefer. Almond and avocado are good options, as is jojoba)
Instructions (Slow Method)
This is the traditionally preferred method because it is thought to preserve the delicate constituents found in comfrey (and other herbs) best. However, sometimes it’s just not practical to wait 4-6 weeks for a batch, so I’ve also included a faster method below.
- Place comfrey leaf or root in a clean, dry glass jar.
- Next, pour in the oil – add enough so that the comfrey is covered by about one-half inch of oil. The reason this is done is that herbs expand as they soak in the liquid, so you add extra to ensure that they stay covered. Comfrey root will stay at the bottom so it’s easy to tell how much to add, but comfrey leaves float so it’s a bit more challenging. What I do is use my thumb to mark the top of the dried comfrey in the jar before I add the oil, then add about 1/2 inch above that.
- Cover the jar with a tight fitting lid and give it a good shake. Place the jar in a paper bag and store near a warm, sunny window. (Some people skip the paper bag, but others believe it helps protect some of the valuable constituents found in comfrey from breaking down due to UV light.) Give the jar a good shake when you walk by it every day.
- Once the oil has been infusing for 4-6 weeks, strain out the herbs and pour the oil in a clean, glass jar. Store in a cool, dark cabinet until needed.
Instructions (Quick Method)
- Place comfrey in a clean, dry glass jar.
- Next, pour in the oil – add enough so that the comfrey is covered by about one-half inch of oil. Comfrey root will stay at the bottom so it’s easy to tell how much to add, but comfrey leaves float so it’s a bit more challenging. What I do is use my thumb to mark the top of the dried comfrey in the jar before I add the oil, then add about 1/2 inch above that.
- Cover your jar with cheesecloth (or a paper towel that is cut into a small square) and secure it with a rubber band.
- Place a kitchen towel in the bottom of your slow cooker and place your jar inside. Add enough water to cover about half the jar and set to the lowest setting for 4-24 hours.My slow cooker has a warm setting so I can infuse it at a very low temperature for 24 hours, but for slow cookers that only have a “low” setting instead of a “warm” setting, I recommend only infusing for 4-8 hours. Leave slow cooker uncovered and allow to infuse, adding water if needed to keep the slow cooker basin from drying out.
- Strain out the oil using cheesecloth and pour the oil in a clean, glass jar. Store in a cool, dark cabinet until needed.
How to make comfrey salve
Comfrey oil doesn’t have to be turned into a salve. However, some people prefer the transferability ease of salves. Also, oils are messy and can attract dust and dirt, so outdoor use of plain oils is usually not practical. To turn the above comfrey oil into a salve, follow this method:
- 4 ounces comfrey infused oil (make your own using the recipe above or buy it here)
- 1/2 ounce by weight beeswax (about 2 tablespoons grated, packed beeswax)
- 25-50 drops essential oil, optional (lavender, frankincense, chamomile and tea tree are good choices)
Gently heat the beeswax in a double boiler. (If you don’t have a double boiler you can use a stainless steel bowl set inside a pot of boiling water.) When the beeswax is melted, add in the comfrey oil. Allow it to warm up for 30-60 seconds, then stir until the beeswax and oil are thoroughly mixed. If you’re adding essential oils, wait until the mixture has cooled just a little and then stir them in.
Pour your salve into a clean, dry container and allow to cool – I used three of these 2 ounce tins. Now you’re ready for the next bug attack, bee sting, scrape, etc.
How to make comfrey plaster
If you want to avoid the time and effort of oils and salves, comfrey leaf and root plasters can be placed directly on unbroken or unabraded skin. Use an immersion blender, regular blender, or just scissors and mortar and pestle to crush the comfrey leaves into a pulp. Then wrap them in gauze, paper towels, or cheese cloth, or place them directly on the skin.
If you live in an area where comfrey only grows part of the year, you can freeze plasters to be used as needed. To freeze, put the gauze, paper towels, or cheese cloth into a freezer safe container and freeze them for future use.
Have you used comfrey before?
Please tell me about your experience in the comments below!
About the authors: This article was coauthored by Heather Dessinger and Dr. Lori Valentine Rose (PhD). Dr. Rose, PhD is a college biology, nutrition, herbal, and wellness instructor, Certified Nutrition Professional (CNP), Registered Herbalist with the American Herbalist Guild, and is Board Certified in Holistic Nutrition. She created, developed, and instructs the Hill College Holistic Wellness Pathway, the most thorough, affordable, degreed wellness program in the country. She loves spreading love and light, and helping others feel awesome on the inside and out so they can live their dreams and make this world more awesome!
Sources for this article:
1. Ganora, Lisa. (2009) Herbal Constituents: Foundations of Phytochemistry
2. Case Reports of Toxicity with Internal Use of Comfrey. Retrieved from https://comfreycentral.com/research/case_reports.htm
3. Barna, M et. al. (2007) Wound healing effects of a Symphytum herb extract cream (Symphytum x uplandicum NYMAN: ): results of a randomized, controlled double-blind study. Retrieved from http://europepmc.org/abstract/med/18157595
4. Kucera, M et. al. (2005) Topical symphytum herb concentrate cream against myalgia: a randomized controlled double-blind clinical study. Retrieved from https://europepmc.org/abstract/med/16510384
5. Grube, B et. al. (2007) Efficacy of a comfrey root (Symphyti offic. radix) extract ointment in the treatment of patients with painful osteoarthritis of the knee: results of a double-blind, randomised, bicenter, placebo-controlled trial.. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/17169543