Comfrey, Coltsfoot and Pyrrolizidine Alkaloids in Teas: Why Regulators Warn
Why official bodies and researchers warn about comfrey, coltsfoot and other plants with pyrrolizidine alkaloids in teas, what liver injury reports describe, and what we could not verify.
Content last updated . This page has not been medically reviewed.
Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.
Urgent first. Pyrrolizidine alkaloids (PAs) can injure the liver. The sources we read describe abdominal pain, an enlarged liver and fluid swelling in the abdomen (ascites) after PA-containing teas. [1][2] If someone has these signs, or a child or adult may have swallowed a plant or tea they cannot identify, call Poison Help at 1-800-222-1222 (US) or 911 in an emergency. Other countries: see poison help by country. This page is information only and gives no preparation steps.
Short answer: comfrey (Symphytum officinale L.) and coltsfoot (Tussilago farfara L.) are plants that can contain PAs, a group of natural compounds with documented liver toxicity. [3][4] Reviews and case reports describe liver injury, and sometimes death, after PA-containing teas. [5][2] PAs can also turn up as contaminants in other herbal teas. [6]
What the terms mean
- Pyrrolizidine alkaloids (PAs): natural plant compounds. More than 660 types have been identified and about 120 of them are hepatotoxic (toxic to the liver). [6]
- Comfrey: Symphytum officinale L. (family Boraginaceae). The EU monograph covers the root, in skin products only. [3][4]
- Coltsfoot: Tussilago farfara L. (family Asteraceae). [3]
- Veno-occlusive disease: the typical liver injury from PAs, a blocking of small liver veins that can lead to cirrhosis and liver failure. [1][5]
Traditional use and what it does not tell us
Traditional use and research are different things. The EMA's committee on herbal medicines (HMPC) accepted a comfrey root preparation as a traditional medicine for minor sprains and bruises, in creams or ointments applied to the skin, for adults only and not for longer than 10 days. [4] That conclusion rests on long-standing use, not on strong clinical trials. [4] A 2000 review notes that in Western Europe comfrey had also been used for conditions such as arthritis and diarrhea, and that the leaves were later recognized as a substantial hazard. [1] Skin use of an approved product says nothing about drinking comfrey as a tea.What official bodies say
| Body, place, year | What it says | Evidence label |
|---|---|---|
| EMA/HMPC, European Union, monograph corrected 31 January 2024 | Animal studies suggest PAs are hepatotoxic after oral administration; the PA amount in the daily dose should be limited to below 1 µg/day for adults; pregnancy and breastfeeding use is not recommended. [7] | Regulatory statement |
| EMA herbal summary for comfrey root (year not shown on the page we read) | Comfrey root contains PAs with toxic effects on the liver by mouth; it states patients should not be exposed to more than 0.35 microgram of PAs per day. [4] | Regulatory statement |
| European Commission (as described in a 2024 review) | Maximum levels of PAs are regulated in certain products. [8] | Regulation, as described by a review |
| Germany and Canada (as reported in a 2000 review) | The review refers to a ban on distributing comfrey in both countries. [1] | Secondhand report, not checked at the source |
The two EMA figures differ (0.35 and 1 µg a day); we report both as the sources state them. Both apply to medicines, not to teas, and are not advice for readers. A clinician or pharmacist decides what is right for a person.
Proper evidence not found for a coltsfoot-specific regulator statement we could read. We searched the EMA herbal pages for coltsfoot under several names (all returned "not found"), and the FDA comfrey advisory and NIH LiverTox pages could not be retrieved. We do not describe them from memory.
What research found
| Question | What the source found | Evidence label |
|---|---|---|
| Can PA-containing teas harm the liver in adults? | Four adults took an unidentified herbal tea daily; three developed ascites, an enlarged liver and abnormal liver tests within 19 to 45 days, one of them died, and all had liver findings of veno-occlusive disease. PAs were found in the brewed tea. [2] | Evidence of harm (case report, 1985) |
| Can it harm a child? | An 18-month-old boy who regularly drank a herbal tea mixture developed veno-occlusive disease and recovered within 2 months. The tea held high PA amounts. [9] | Evidence of harm (case report, 1995) |
| Is coltsfoot the cause? | In that case the parents thought they had coltsfoot, but analysis found a different plant, Adenostyles alliariae, and the authors say identity should be checked by trained experts. [9][3] | Case report: look-alike mix-up |
| How serious can acute PA toxicity be? | High PA exposure may lead to liver failure and even death, as documented by case reports. [5] | Evidence of harm (risk assessment) |
| Do PAs get into the cup? | In controlled lab tests, 30% to 68% of PAs and tropane alkaloids transferred from contaminated black and herbal tea into the infusion, average 49%. [10] | Laboratory study |
| Are other herbal teas affected? | A study of 203 rooibos samples from 18 European countries found PAs in 98% of them, all below the EU maximum level of 400 µg/kg. [11] | Product survey |
| Do extracts of these plants harm living cells? | Dry extracts of Symphytum officinale, Tussilago farfara and others were toxic to two small aquatic animals. [12] | Preclinical (animals) |
Limits and uncertainty
Most human evidence is a small set of case reports and reviews, not controlled trials, so no one can say how much tea is "safe". The studies above looked at specific plants, products and amounts; results for one tea do not transfer to another. Tea contamination studies report PA levels in dried material and in infusions, and one study says teas should be analyzed as infusions for realistic exposure estimates. [10] Whether a particular product on a shelf contains PAs is not something a reader can tell by looking, which is why this page does not offer identification or preparation advice.Safety and who should ask a clinician
- Liver conditions, pregnancy and breastfeeding: EMA says pregnancy and breastfeeding use of comfrey root products is not recommended because safety is not established. [7] See pregnancy and breastfeeding and liver safety.
- Medicines: none were reported to interact with the skin product in the EMA monograph, but that does not cover drinking comfrey. [7] Ask a pharmacist; see how interactions work.
- Look-alike plants and mislabeled products: do not rely on a photo or app; ask a poison center or an expert local botanist. See plant and mushroom poisoning and product quality and contamination.
- Before surgery or if you have liver disease: tell the care team about every herbal tea you drink.
Related reading: the comfrey profile, herbs and liver injury, herbal tea adulteration, mold and mislabeling and herbal tea, the liver and kidneys.
Frequently asked questions
Why do regulators warn about comfrey tea?
Comfrey contains PAs, which the EMA says have toxic effects on the liver when taken by mouth. [4] Reviews describe veno-occlusive disease as the main liver injury. [1]
Is coltsfoot tea safe?
Proper evidence not found that it is safe. Coltsfoot (Tussilago farfara) was named in an infant liver injury report, though the plant in that tea turned out to be a look-alike. [9] An extract of coltsfoot was toxic to small animals in a lab study. [12] We could not read a regulator statement on coltsfoot.
Can ordinary herbal teas contain PAs?
Yes, as contaminants. A review says PAs are found in spices, herbal teas, honey and milk. [6] A rooibos survey found PAs in 98% of samples, all below the EU maximum level. [11]
Does brewing longer remove PAs?
In one lab study brewing time was not a significant factor; the acidity of the infusion and the compounds' chemistry mattered more. [10] This is a lab finding, not advice.
What should I do if I think I drank a PA-containing tea?
Ask a pharmacist, clinician or Poison Help (1-800-222-1222 in the US) about it, and get medical care quickly if there is abdominal pain or swelling, which the sources we read describe. [1][2] The liver safety page lists more warning signs.
References
- Stickel F, Seitz HK. The efficacy and safety of comfrey. Public Health Nutr. 2000. PubMed 11276298. Read 2026-10-23.
- Herbal tea induced hepatic veno-occlusive disease: quantification of toxic alkaloid exposure in adults. Gut. 1985. PubMed 3965360. Read 2026-10-23.
- GBIF Secretariat. GBIF Backbone Taxonomy, species match API for Symphytum officinale L., Tussilago farfara L., Adenostyles alliariae (Gouan) A.Kern., Mitragyna speciosa Korth., Ilex paraguariensis A.St.-Hil., Senna alexandrina Mill. (all returned ACCEPTED). Read 2026-10-23.
- European Medicines Agency, HMPC. Symphyti radix (comfrey root): herbal medicinal product summary. Page undated in the text we read. Read 2026-10-23.
- Risk assessment of short-term intake of pyrrolizidine alkaloids in food: derivation of an acute reference dose. Food Addit Contam Part A, 2023. PubMed 36794362. Read 2026-10-23.
- Levels, Toxic Effects, and Risk Assessment of Pyrrolizidine Alkaloids in Foods: A Review. Foods. 2024. PubMed 38397512. Read 2026-10-23.
- European Medicines Agency, HMPC. European Union herbal monograph on Symphytum officinale L., radix, EMA/HMPC/572846/2009 Corr1, 31 January 2024. Read 2026-10-23.
- Pyrrolizidine Alkaloids as Hazardous Toxins in Natural Products: Current Analytical Methods and Latest Legal Regulations. Molecules. 2024. PubMed 39064851. Read 2026-10-23.
- Reversible hepatic veno-occlusive disease in an infant after consumption of pyrrolizidine-containing herbal tea. Eur J Pediatr. 1995. PubMed 7720737. Read 2026-10-23.
- Transfer of pyrrolizidine and tropane alkaloids from tea and herbal tea to infusions. Food Chem. 2025. PubMed 40483819. Read 2026-10-23.
- Occurrence of tropane alkaloids, pyrrolizidine alkaloids and mycotoxins in rooibos: a comprehensive safety assessment. Food Addit Contam Part A. 2026. PubMed 42615889. Read 2026-10-23.
- Toxicity of plant extracts containing pyrrolizidine alkaloids using alternative invertebrate models. Mol Med Rep. 2018. PubMed 29620235. Read 2026-10-23.