What Is Comfrey? What Are Its Uses And Side Effects?

Medically reviewed by Vd. Babita Sharma, Ayurveda Physician
by Swathi Handoo

Comfrey’s use in medicine dates back to the era of ancient Greeks and Romans. The roots and aerial parts of this plant were used in ancient medicine to manage sprains, arthritis, digestive disturbances, and skin ailments (1).

The presence of a unique biochemical called allantoin makes this herb a powerful tissue regenerator. However, high levels of another bunch of unique phytochemicals (alkaloids) in comfrey may cause organ damage and cancer. So, is comfrey unsafe for you? What do the researchers say about using this plant? What’s the verdict?

In this article, we will explore the answers to these questions, along with a few others.

Comfrey: In Detail

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Comfrey (Symphytum officinale) is an herb belonging to the Boraginaceae family. The plant has been cultivated as a healing herb since 400 BC in Europe and Asia (1), (2).

It is primarily a food and forage crop. But research has proven its therapeutic properties. In fact, the ancient Greeks, Native Americans, and Romans used comfrey to stop heavy bleeding, treat bronchial problems, and heal broken bones (1).

Comfrey poultices were used for curing external wounds. Drinking its tea could heal internal ailments.

The plant parts have active biochemicals, like allantoin, rosmarinic acid, polysaccharides, alkaloids, saponins, etc. These molecules are responsible for the pain-relieving, wound-healing, and anti-inflammatory properties of comfrey (1), (2), (3).

 However, modern research has raised concerns over the safety of this plant. Before we get to that, let’s take a quick look at the proven benefits of comfrey. Swipe up!

What Are The Benefits Of Comfrey?

Comfrey heals wounds, muscle pain, burns, ulcers, fractures, and inflammation. It accelerates recovery from such injuries because of its biochemical ingredients.

1. Accelerates Wound Healing

The leaves and other aerial parts of comfrey have potent wound-healing properties. When applied topically for 2-3 days, the wounds show faster initial reduction (3).

Studies report an increase in collagen deposit (about 8%) at the treated site. Also, the active biochemicals reduce the migration (infiltration) of pro-inflammatory components to the affected site (4).

According to lab trials, an oil-water emulsion of comfrey leaves is said to be the most effective treatment for open wounds (4).

2. Relieves Back Pain

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Upper and lower back pain is a prevalent condition. It impairs the functional movement and quality of life in affected individuals. Pain/ache of this nature is typical and challenging to treat in one-go (5).

Commonly, non-steroidal anti-inflammatory drugs (NSAIDs) are administered to manage the pain. A majority have received this approach well. Herbal medicine has also shown comparable results (with Diclofenac) in managing acute back pain. Herbs like comfrey can substitute NSAIDs in an alternative approach (5), (6).

Several lab trials show a significant difference between subjects who are treated with comfrey and those who are not. Comfrey was found to decrease pain intensity by about 33% in just the first hour of treatment (5), (6).

However, the effect of topical comfrey formulations needs more research (5).

3. Hydrates And Repairs Skin

The comfrey root extract has active compounds. They include allantoin, rosmarinic acid, caffeic acid, polysaccharides, mucilage, and protein complexes. Allantoin stimulates the proliferation of healthy cells. Hence, it can remove scars and blemishes on your skin (6), (7).

Rosmarinic acid and caffeic acid inhibit the synthesis of  pro-inflammatory compounds. Polysaccharides and mucilage hydrate and moisturize your skin. They cool your skin down by calming the nerve endings (6), (7).

Therefore, this extract heals ulcers and irritation. About 5-10% of this extract could effectively reduce skin damage induced by UV rays (redness, sunburns, etc.). Creams with comfrey ingredients are used to treat insect bites and painful boils (abscesses, furuncles, carbuncles) (3), (6), (8).

4. Boosts Bone Health

Traditional practices use comfrey (Symphytum uplandica) tea and root extract to promote healing of bone fractures and sprains. It was used in plasters and poultices to set and cure broken bones, thereby giving it the name ‘knit bone’ (9), (10).

Homeopathic preparations of this herb (6CH) have shown to boost bone density in study subjects. Comfrey may also treat swelling around bone and titanium implants (11).

Comfrey is also externally applied to manage the inflammation of bone joints. With further research, comfrey may be applied to heal chronic bone diseases like rheumatoid arthritis and osteoarthritis (12).

Trivia Time!

  • The anti-inflammatory properties of comfrey may help treat digestive, respiratory, and other inflammatory disorders (including ulcers, gout, and irritable bowel disease) (13).
  • But, scientific studies have not shown a green flag yet. Comfrey may have adverse effects on your health. Using it as the principal anti-inflammatory agent may not be a great idea (13).
  • The active ingredient in this plant, allantoin, is a powerful growth stimulant. You can find comfrey extracts in skin, hair, and dental care products (14).
  • But the effectiveness of allantoin rich-comfrey extract compared to pure allantoin is still being studied. There is insufficient data to prove the safety of comfrey in cosmetic use.
  • In optimal concentrations, this herb can be included in veterinary medicine. You can use comfrey poultices, plasters, and other preparations on animals too (1).

5. Might Have Anti-Cancer Effects

Research links comfrey to several cancers. But recent studies have demonstrated anti-cancer properties in its extracts. The extracts also have strong antioxidant, anti-inflammatory, and immunity-boosting effects (15), (16).

The active molecules in comfrey could induce cell death in cancerous cells of the prostate, liver, and blood. They also interfere in the critical stages of cancer development, like cell division and angiogenesis (15), (16).

Moreover, comfrey extracts showed no toxicity in the subjects of these trials. How comfrey manages to be a carcinogen and yet treats/manages certain cancers remains a mystery. Research is ongoing to understand this dual mechanism (15), (16).

According to experimental data, such benefits are because of the unique phytochemical profile of comfrey.

Its roots, leaves, and other parts have varying amounts of polyphenolic components. Find out more about these components in the next section.

Biochemical Composition Of Comfrey

Comfrey roots are abundant in allantoin and mucilage that is made of fructose and glucose molecules. Rosmarinic, caffeic, and chlorogenic acids were identified in chemical analyses. The presence of saponins, terpenoids, and alkaloids has also been reported (3).

The leaves are also a reserve of allantoin and alkaloids. The alkaloids have received a lot of attention from the scientific community in recent times (17).

Experiments on comfrey root and leaf extracts have revealed that these active molecules (alkaloids) can cause cancer.

Hence, wild or common comfrey is considered toxic/unsafe for humans (and animals). Read on to know the side effects of comfrey in detail.

Is Comfrey Toxic To Your Body? What Are The Side Effects?

Due to the presence of pyrrolizidine alkaloids, comfrey is considered unfit for human ingestion (especially via the oral route).

The leaves and roots of comfrey possess symphytine, symlandine, and echimidine, which make a unique set of pyrrolizidine alkaloids. Chronic ingestion of these molecules causes liver toxicity, kidney disease, hypertension, and skin allergies (13).

Moreover, a few cases demonstrate the carcinogenic (cancer-causing) properties of comfrey (12).

Such effects make comfrey and its extracts unsafe for pregnant and lactating women (17).

Some countries like Germany, UK, and Canada have either banned or restricted the use of this herb in medicine/treatment.

The American Herbal Products Association recommends comfrey to be used only externally. In 2001, the U.S. Food and Drug Administration (FDA) advised dietary supplement manufacturers to remove comfrey products from the market (12).

However, the safety of comfrey remains undecided. Some countries have no restrictions on using comfrey, to date.

You can also find comfrey supplements in various forms on the internet and market.

Read the next section to know how to get these products.

How To Use Comfrey? Where To Buy It?

It is best to use comfrey topically. Oral consumption may not be beneficial for your health because of the presence of alkaloids and other toxic phytochemicals.

Pain relief creams (Buy here!), cosmeceutical lotions, ointments (Buy here!), oils (Buy here!), herbal salve (Buy here!), etc. are the common products of comfrey.

It is also available over-the-counter (OTC) as a remedy for sprains, wounds, cuts, rashes, and so on.

Comfrey tea is a popular product of this plant. You can brew dried comfrey leaves to make a therapeutic tea that is known to relieve bone pain.

If you wish to try comfrey tea, you can buy the dried leaves here. Here’s how you make it:

How To Make Comfrey Tea

  • Add 1–2 teaspoons of the dried comfrey leaves to a teapot.
  • Pour 1- 1½ cups of boiling water over the leaves.
  • Let it steep for 10-20 minutes.
  • Strain into serving cups and drink warm.

Given the adverse effects of this plant, is there a recommended dose of comfrey tea/extracts? Scroll down to know.

What Is The Recommended Dose Of Comfrey?

If it is comfrey tea, split a cup of it into small doses. Take it four times a day (10).

If it is a tincture, use 5-20 drops four times daily. Use only freshly-made poultices of dried or fresh comfrey leaves (10).

You also need to keep the duration of treatment in mind. Prolonged usage of comfrey would set in adverse effects because of the toxic alkaloids.

Instead, try using PA-free (pyrrolizidine alkaloids free) extracts. Or search for comfrey products that have less than 10 µg of these alkaloids. They would be within/below its daily allowance limit (3).

In Summary

Comfrey is a traditional remedy for broken bones, sprained ankles, open wounds, and an aching back. Ancient Romans swore by its poultices, salves, creams, and teas to treat chronic ailments.

But scientists have identified active molecules in comfrey that may cause cancer and liver injury. Therefore, it is recommended to talk to your doctor about using comfrey. Do not self-medicate. Most importantly, find out if comfrey is legal in your country.

If all goes well, you might be relieved of that nagging backache after using it! In that case, do share your experiences with us by leaving a comment in the box below!

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Swathi Handoo

Swathi holds a Master’s degree in Biotechnology and has worked in places where actual science and research happen. Blending her love for writing with science, Swathi writes for Health and Wellness and simplifies complex topics for readers from all walks of life.And on the days she doesn’t write, she learns and performs Kathak, sings Carnatic music compositions, makes plans to travel, and obsesses over cleanliness.
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