Comfrey tea is made the same way as most herbal teas: pour boiling water over dried or fresh leaves, steep for several minutes, and strain. The recipe itself is simple. The problem is that comfrey contains a family of toxic compounds called pyrrolizidine alkaloids that can cause serious, sometimes fatal liver damage. Comfrey has been consumed as a tea and a vegetable for more than two thousand years, but the accumulated evidence against drinking it is now strong enough that health authorities in the United States, the European Union, and Australia have either banned or restricted its sale for internal use.
The Traditional Recipe
Since the title asks how to make it, here is what traditional herbalists and older recipe books describe. Dried comfrey leaves, typically one to two teaspoons, are placed in a mug and covered with boiling water. The tea steeps for ten to fifteen minutes, is strained, and served. Some recipes call for fresh young leaves instead of dried ones, and a few older sources suggest adding honey or lemon to mask the mildly bitter, mucilaginous taste. The resulting liquid is green to golden-brown and has a grassy, slightly earthy flavor. That is the entire process. There is nothing complicated about it, which is part of the reason people still stumble into making it after reading about comfrey’s long folk-medicine reputation for healing bones and soothing digestive complaints.
The simplicity of the recipe is also what makes it deceptively dangerous. Unlike, say, preparing a pufferfish, where the risk is obvious and the skill required is extreme, making comfrey tea looks and feels identical to brewing chamomile or peppermint. Nothing about the process warns you that the cup in your hand contains compounds your liver may not be able to handle.
What Pyrrolizidine Alkaloids Do to Your Liver
Comfrey contains as many as fourteen different pyrrolizidine alkaloids, including symphytine, echimidine, lycopsamine, intermedine, and lasiocarpine, among others.1PubMed Central. Metabolism, genotoxicity, and carcinogenicity of comfrey These compounds are not immediately poisonous in the way that, say, cyanide is. They need to be processed by your liver’s own enzymes before they become harmful. Once activated inside the liver, the metabolites bind to DNA in liver cells and the cells lining the liver’s small blood vessels. The damage tends to be cumulative rather than sudden, which means a person can drink comfrey tea for weeks or months feeling perfectly fine before symptoms appear.
The specific type of liver injury most commonly linked to comfrey is called hepatic veno-occlusive disease, now more often referred to as sinusoidal obstruction syndrome. In plain terms, the tiny veins inside the liver become blocked and scarred. Blood backs up, liver tissue dies from lack of flow, and the organ progressively fails. Symptoms include abdominal pain, a swollen liver, fluid buildup in the abdomen, and jaundice. By the time these symptoms become obvious, the damage can be severe and, in some cases, irreversible.
People Who Got Sick or Died
The medical literature includes several case reports that connect comfrey tea directly to this kind of liver destruction. A 47-year-old woman developed veno-occlusive disease after drinking comfrey-containing herbal tea daily for about four months; her liver biopsy confirmed the characteristic changes.2PubMed Central. Veno-occlusive disease of the liver secondary to ingestion of comfrey In another case, a 23-year-old man on a vegetarian diet who had been consuming comfrey leaves presented with severe portal hypertension and widespread liver-cell death. His liver biopsy and imaging showed occlusion of the small veins throughout the liver, and he ultimately died from liver failure.3PubMed. Hepatic veno-occlusive disease associated with comfrey ingestion A separate published case similarly documented comfrey herb tea as the cause of hepatic veno-occlusive disease.4PubMed. Comfrey herb tea-induced hepatic veno-occlusive disease
These cases are not flukes buried in obscure journals. They come from mainstream gastroenterology and internal medicine publications, and they share a consistent pattern: a person consumes comfrey internally over weeks to months, develops liver symptoms, undergoes biopsy, and shows the hallmark vascular damage that pyrrolizidine alkaloids are known to cause. In each instance, other potential causes of the disease were investigated and ruled out, leaving comfrey as the most plausible explanation. The 23-year-old’s death is a particularly sobering reminder that this is not a risk confined to frail or elderly people.
Leaves vs. Roots and the “Safe Part” Myth
A common claim in herbal communities is that comfrey leaves are relatively safe and that the dangerous alkaloids are concentrated in the roots. There is a grain of truth here, but it badly misleads. Research on Polish comfrey samples confirmed that roots do contain more pyrrolizidine alkaloids than leaves, and that the alkaloid profiles in roots vary widely depending on growing conditions and geographic origin, while leaf profiles tend to be more stable.5PubMed Central. LC-MS/MS Evaluation of Pyrrolizidine Alkaloids Profile in Relation to Safety of Comfrey Roots and Leaves from Polish Sources “Lower” does not mean “low enough.” The case reports described above involved leaf consumption, not root consumption. And there is another wrinkle that makes the picture worse than simple alkaloid counts suggest.
Pyrrolizidine alkaloids exist in comfrey in two chemical forms: the free-base form and the N-oxide form. When researchers analyzed teas prepared from commercially purchased comfrey leaves using methods consistent with how consumers actually brew them, they found that chemically reducing the N-oxides to their parent alkaloids increased the measurable concentration of the key toxins by an order of magnitude.6PubMed. Analysis of herbal teas made from the leaves of comfrey (Symphytum officinale): reduction of N-oxides results in order of magnitude increases in the measurable concentration of pyrrolizidine alkaloids In practical terms, the gut bacteria in your digestive tract can perform a version of this same reduction, converting N-oxides back into the toxic parent compounds after you swallow the tea. So a test that measures only free-base alkaloids in the cup dramatically underestimates your actual exposure. Anyone telling you that leaf tea has been tested and found safe may be relying on analyses that missed the bulk of the problem.
Comfrey and Cancer
Liver damage from veno-occlusive disease is the acute risk, but comfrey also carries a longer-term concern. The metabolites of its pyrrolizidine alkaloids form adducts with DNA, meaning they chemically bond to your genetic material in ways that can cause mutations and, eventually, tumors. A study using a transgenic rat model found that rats fed comfrey had a mutation frequency in liver tissue roughly five times higher than control rats. In a related carcinogenicity study, rats receiving a diet containing 2% comfrey root developed liver tumors at a rate of 42%, while no liver tumors appeared in the control group.7British Journal of Cancer. Mutagenicity of comfrey (Symphytum Officinale) in rat liver The correspondence between mutation induction and tumor formation strongly suggests that comfrey causes cancer through direct DNA damage rather than some indirect route.
A broader review of comfrey’s genotoxicity concluded that the activated metabolites interact with DNA in both liver endothelial cells and hepatocytes, producing a consistent profile of DNA adducts and mutation patterns.1PubMed Central. Metabolism, genotoxicity, and carcinogenicity of comfrey This is important because it means the damage is not random or unpredictable: comfrey’s alkaloids leave a recognizable molecular fingerprint. Whether a person who drank comfrey tea occasionally for a few months decades ago has a meaningfully elevated cancer risk is hard to say with precision, but the mechanism is well established in animal models. The cumulative nature of DNA damage is the reason oncologists and toxicologists treat any genotoxic exposure as a “less is better” situation, with no clear safe threshold.
Why People Still Recommend It
Comfrey’s folk-medicine pedigree is genuinely old. It has been used as a food and a medicine for over two thousand years, long predating any understanding of pyrrolizidine alkaloid toxicity.1PubMed Central. Metabolism, genotoxicity, and carcinogenicity of comfrey Its common name, “knitbone,” reflects the long-standing belief that it speeds the healing of fractures. It was also used for stomach ulcers, bronchial complaints, and wound healing. In many pre-industrial communities, comfrey was a trusted household remedy. That cultural momentum did not vanish when the toxicological evidence arrived in the late twentieth century.
Modern recipe websites and social-media herbalism accounts sometimes frame the regulatory bans as overreach, arguing that the case reports involve unusually high consumption or that leaf tea is different from root preparations. The sources reviewed here make clear that leaf consumption has been directly implicated in serious liver disease and that standard brewing methods release more toxin than casual testing reveals. The recipes circulate because the internet rewards confidence and tradition over nuance, and because comfrey genuinely does contain allantoin and other compounds with real wound-healing properties. The mistake is assuming those benefits transfer safely from external poultices to an internal drink.
Topical Comfrey Is a Different Story
If you have heard that comfrey creams and ointments are available at pharmacies in Europe and wonder how that squares with everything above, the answer lies in skin absorption. Multiple randomized controlled trials have demonstrated that topical comfrey preparations are effective for treating pain, inflammation, and swelling from conditions like osteoarthritis, back pain, sprains, and sports injuries, including in children aged three and older.8PubMed Central. Comfrey: a clinical overview These products work and are considered safe for external use because pyrrolizidine alkaloids cross the skin barrier poorly.
A skin-penetration study found that after 24 hours, the alkaloid lycopsamine had not detectably migrated through the skin in five of six test setups, and even in the worst-case scenario, the theoretical skin penetration was under 5% of the applied dose, a figure the researchers noted was likely a significant overestimate due to conservative assumptions.9PubMed. Safety of medicinal comfrey cream preparations (Symphytum officinale s.l.): The pyrrolizidine alkaloid lycopsamine is poorly absorbed through human skin In other words, the skin acts as an effective barrier that the gut does not. Rubbing comfrey cream on a sore knee is a completely different proposition from pouring comfrey extract down your throat. Regulated topical comfrey products in Europe are also formulated to minimize alkaloid content, adding another layer of safety. The distinction matters because some people hear “comfrey is dangerous” and throw out their joint cream, which is an overcorrection based on a misunderstanding of the route of exposure.
Pyrrolizidine Alkaloids Are Not Unique to Comfrey
Comfrey gets the most attention, but pyrrolizidine alkaloids occur in hundreds of plant species. They can contaminate common herbal teas and honey when bees forage on PA-containing plants or when PA-producing weeds grow alongside tea crops. A survey of retail teas and honeys in Berlin found total PA concentrations in tea samples ranging from undetectable to over 5,600 micrograms per kilogram, while honey averaged about 10 micrograms per kilogram.10PubMed. Determination of pyrrolizidine alkaloids in tea, herbal drugs and honey These are not teas marketed as containing comfrey; they are ordinary black, green, rooibos, chamomile, peppermint, and fennel teas that happened to be contaminated.
The European Food Safety Authority assessed this broader exposure and concluded that there is a possible health concern related to pyrrolizidine alkaloid intake, particularly for people who are frequent and high consumers of tea and herbal infusions.11PubMed Central. Risks for human health related to the presence of pyrrolizidine alkaloids in honey, tea, herbal infusions and food supplements This does not mean your morning cup of chamomile is as dangerous as comfrey tea. The concentrations in comfrey are vastly higher than in incidentally contaminated products. But it does mean that the class of toxin is more widespread in the food supply than most people realize, and that anyone interested in minimizing their PA exposure should be aware that comfrey is the extreme end of a broader spectrum.
Comfrey in the Garden
If you have comfrey growing in your yard or are thinking about planting it, there is a perfectly productive use for it that involves no drinking whatsoever. Comfrey is widely valued in organic gardening as a nutrient-rich mulch and liquid fertilizer. Its deep taproot mines minerals from the subsoil, concentrating potassium and other nutrients in the leaves. Gardeners chop the leaves and either lay them directly around plants as mulch, or steep them in water to create a concentrated liquid feed. A comparative study found that organic comfrey liquid fertilizer produced the highest mean tomato yield per plant among the treatments tested, outperforming both a standard inorganic fertilizer and unfertilized controls by a wide margin.12International Journal of Advanced Multidisciplinary Research and Studies. A Comparative Analysis of the Impact of Organic Comfrey Liquid Fertilizer and Inorganic Fertilizer on the Growth and Yield of Tomato (Solanum Lycopersicum) The comfrey-fed plants also showed greater height and leaf development, particularly in later growth stages.
The pyrrolizidine alkaloids in comfrey do not transfer to the vegetables you grow with comfrey fertilizer in any meaningful amount, so this use raises no food-safety concerns. Many permaculture practitioners consider comfrey one of the most useful plants in their gardens precisely because it is so productive and so good at cycling nutrients. The variety most commonly recommended for garden use is “Bocking 14,” a sterile hybrid of Russian comfrey that does not self-seed aggressively and has particularly high potassium content in its leaves. If you have a comfrey patch and have been wondering whether to brew it into tea or brew it into plant food, the plant food is the right answer in every respect.
What About Livestock
Comfrey’s toxicity is not limited to humans. The pyrrolizidine alkaloids it contains are hepatotoxic in animals as well, and some have been shown to induce tumors in experimental animals.13PubMed. Comfrey: assessing the low-dose health risk Historically, comfrey was grown as a fodder crop for pigs and poultry, and it was even promoted for this purpose in some agricultural extension materials. Livestock that graze on comfrey or are fed comfrey-containing hay can develop the same kind of progressive liver damage seen in humans, though the timeline and dose required vary by species. Horses and cattle appear to be more susceptible than sheep, which can tolerate somewhat higher levels of pyrrolizidine alkaloids due to differences in how their digestive systems process the compounds. If you keep animals and have comfrey in your pasture, it is worth knowing that most grazing animals will avoid it when other forage is available because of its rough, hairy leaves. Problems tend to arise when comfrey is mixed into hay or silage, where animals cannot selectively avoid it, or when pasture quality is poor and animals eat whatever is available.