Comfrey Root: The Controversial Healer
Let me tell you about the plant that makes people nervous.
Comfrey — Symphytum officinale — has been used by healers for over two thousand years. Its common names tell you everything about its traditional reputation: knitbone, boneset, bruisewort, healing herb. These are not the names of a plant that people were ambivalent about. These are the names of a plant that worked — visibly, reliably, in ways that left an impression strong enough to survive in language for centuries.
And yet, if you search "comfrey" online today, you will find warnings. FDA advisories. Headlines about liver damage. Recommendations to avoid it entirely.
So which is it? A time-honored healer or a dangerous herb?
The honest answer — the one that requires actually reading the research rather than just the headlines — is more nuanced than either extreme. And I think you deserve the nuanced answer.
A Brief History of a Very Old Plant
Comfrey's medicinal use is documented as far back as ancient Greece, where Dioscorides — the physician whose herbal text De Materia Medica remained the standard reference for over 1,500 years — described it for wound healing and bone repair. The name Symphytum comes from the Greek symphyo, meaning "to unite" — a reference to its traditional use for bringing broken things back together.
In medieval European herbal tradition, comfrey was one of the most widely used medicinal plants. It grew in monastery gardens, in cottage gardens, in the herb beds of every healer who had access to it. It was used as a poultice for wounds, bruises, sprains, and fractures. It was used as a compress for inflamed joints. It was used, in various preparations, for skin conditions ranging from eczema to ulcers.
This is not a thin historical record. This is two thousand years of consistent, cross-cultural use for a specific set of applications — and that kind of record deserves to be taken seriously, even as we subject it to modern scrutiny.
Growing up, we knew it as comfrey or boneknit - and grandma had it planted EVERYWHERE. Fun fact - comfrey is also a fantastic plant for your compost! More on that later.
The Controversy: What It Actually Is
In the 1980s, researchers identified a class of compounds in comfrey called pyrrolizidine alkaloids — or PAs. These compounds, present in varying concentrations in different parts of the plant (highest in the root, lower in the leaves), were found to be hepatotoxic — capable of causing liver damage — when consumed internally in significant quantities.
This finding was significant and legitimate. Internal consumption of comfrey — as a tea, a tincture, or a food — carries real risk, particularly with long-term or high-dose use. Several countries have restricted or banned the sale of comfrey for internal use. The FDA has issued warnings against consuming comfrey internally. These warnings are appropriate and I support them fully.
But here is where the nuance matters enormously, and where I think the public conversation has done people a disservice:
The research on pyrrolizidine alkaloid toxicity is almost entirely based on internal consumption — not topical application.
The liver damage associated with PAs occurs because, when ingested, these compounds are metabolized by the liver into toxic metabolites. The question of whether topically applied comfrey poses the same risk is a fundamentally different question — one that requires looking at dermal absorption rates, the concentration of PAs in topical preparations, and the metabolic pathway of dermally absorbed compounds.
And when you look at that research specifically, the picture is considerably more reassuring. Realistically, the quantity of comfrey ingested in the studies was way, way more than any reasonable human would be able to consume.
What the Research on Topical Comfrey Actually Shows
I want to be careful here, because I am not a toxicologist, and I am not making safety claims about any specific product. What I can do is share what the published research says and let you draw your own informed conclusions.
On dermal absorption of pyrrolizidine alkaloids:
Studies examining the dermal absorption of PAs from comfrey preparations have found that absorption through intact skin is low — significantly lower than absorption through the gastrointestinal tract. A a study from 2017 as well as a more recent study in 2020, both published in Science Direct, examined the systemic availability of PAs from a topical comfrey root extract preparation and found that dermal absorption was minimal under normal use conditions - and concluded that the risk of topical preparations is overestimated.
On the safety of topical comfrey preparations:
The European Medicines Agency (EMA) — the regulatory body responsible for evaluating medicinal products in the European Union — has issued a positive assessment for topical comfrey root preparations for the relief of muscle pain, sprains, and bruises. Their assessment concluded that topical use of comfrey root preparations is acceptable when used on intact skin for limited periods, and that the benefit-risk balance for topical use is favorable.
This is not a fringe position. This is the considered conclusion of one of the world's most rigorous pharmaceutical regulatory bodies, based on a comprehensive review of the available evidence.
On the concentration of PAs in topical preparations:
The EMA's guidelines for topical comfrey preparations specify a maximum daily PA exposure of 100 micrograms — a threshold that well-formulated topical products remain well below under normal use conditions. The key variables are the concentration of comfrey in the preparation, the PA content of the specific plant material used, and the amount applied.
The Traditional Wisdom, Revisited
Here is something I find genuinely interesting about the comfrey story: traditional herbalists, long before anyone had identified pyrrolizidine alkaloids or understood their mechanism of toxicity, had already arrived at a set of use guidelines that align remarkably well with what modern research supports.
Traditional herbal texts consistently recommend comfrey for external use. The internal use of comfrey — while documented in some traditions — was never the primary application. The poultice, the compress, the salve, the infused oil: these are the forms in which comfrey has been most consistently and most enthusiastically recommended across cultures and centuries.
Traditional herbalists also consistently recommended against applying comfrey to broken skin or open wounds — not because they understood PA absorption, but because they observed, empirically, that this was the appropriate boundary for its use.
Modern research has given us the mechanism behind that traditional wisdom. The traditional wisdom got there first.
What Comfrey Is Known For — And Why We Use It
With all of that context established, let me tell you what comfrey is actually known for in the herbal tradition and in the research literature — and why it earns its place in Rainroot formulas.
Allantoin
The compound most associated with comfrey's skin-supportive properties is allantoin — a naturally occurring constituent found in significant concentrations in comfrey root. Allantoin is well-studied, widely used in cosmetic formulations, and recognized by the FDA as a safe and effective skin protectant ingredient.
Allantoin is known for its ability to support the skin's natural renewal processes, its soothing properties on irritated skin, and its role in maintaining skin comfort and softness. It is one of the reasons comfrey has such a long traditional association with skin recovery — and one of the reasons it remains relevant in modern botanical skin care.
Rosmarinic acid
Comfrey also contains rosmarinic acid — a polyphenol with well-documented antioxidant properties that is found in a number of medicinal plants including rosemary, sage, and lemon balm. Rosmarinic acid is known for its skin-supportive properties and contributes to comfrey's overall profile as a botanical ingredient.
Traditional vulnerary action
Beyond specific compounds, comfrey has a two-thousand-year track record as a vulnerary herb — one traditionally used to support the skin's natural recovery processes. That record, combined with the modern research on allantoin and rosmarinic acid, gives us a reasonably clear picture of why this plant has been so consistently valued.
How We Use Comfrey at Rainroot
Given everything above, here is our approach to comfrey — transparent, considered, and consistent with both traditional practice and current research:
We use comfrey leaf and root — slow-infused in our rice bran and sunflower oil blend — as a key ingredient in our most therapeutic formulas, including our First Aid Salve.
We use it only in topical preparations — never in any ingestible product. This is consistent with both traditional guidance and modern regulatory recommendations.
We apply it only to intact skin — our product directions specify this clearly, consistent with traditional practice and the EMA's guidelines.
We are transparent about its presence — comfrey root appears clearly on every ingredient list where it is used, in both INCI format and plain language, so that every customer can make an informed decision.
We do not make drug claims — comfrey is an ingredient with a long traditional history and an interesting research profile. What it does in any specific product, for any specific person, is not something we claim to know or control. We include it because it is known for its skin-supportive properties, and because the traditional record and the available research both support its topical use on intact skin.
The Bigger Picture
The comfrey story is, I think, a useful lens for thinking about herbal medicine more broadly.
The narrative that "natural equals safe" is wrong — comfrey's internal use risks are a clear example of why. But the counter-narrative that "if it has any risk it should be avoided entirely" is also wrong — it flattens a nuanced picture into a useless binary and throws away two thousand years of carefully accumulated knowledge in the process.
The truth is more interesting and more useful than either extreme: plants are complex, their effects depend on how they are used, and the appropriate response to complexity is not fear but careful, informed engagement.
That is what traditional herbalists did. That is what good modern research does. And that is what I try to do in every formula I make — hold the traditional knowledge and the modern evidence together, let them inform each other, and arrive at something that is both rooted in the past and honest about what we currently know.
Comfrey has earned its place in this apothecary. Two thousand years of healers reaching for it, and a growing body of research explaining why — that is not nothing.
That is, in fact, quite a lot.
— Briana, The Village Wisewoman, Renton, Washington
⚠️ Disclaimer: This post is for informational and educational purposes only and does not constitute medical advice. Comfrey is recommended for external use on intact, unbroken skin only. This product is not intended to diagnose, treat, cure, or prevent any disease or health condition. If you have a known liver condition or are pregnant or breastfeeding, consult your healthcare provider before using products containing comfrey.
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