What centuries of traditional use can and can’t tell you

Key takeaways

• The European Union registers herbal medicines on tradition alone after 30 years of use, 15 of them in the EU, without requiring clinical trials⁵.
• Health Canada lets products carry traditional claims but bars them for serious diseases and for conditions a tradition couldn’t diagnose, such as high cholesterol⁷.
• A 2001 count found 122 plant compounds approved worldwide as single-ingredient medicines, and at least 80% of them traced back to a plant’s traditional medical use¹¹.
• Tradition missed comfrey’s liver toxicity when taken by mouth, and in 2001 the FDA urged companies to pull comfrey supplements from the market⁴.
• Before you try an herb, place it on the ladder in this article: the lower its rung, the milder the problem you should use it for.

Comfrey’s old nicknames include knitbone and bruisewort¹. For centuries, its leaves and roots were used to help heal wounds and calm inflammation¹.

In 2015, the European Union’s committee on herbal medicines gave part of that tradition an official nod. It accepted comfrey root creams and ointments for easing minor sprains and bruises, based on long-standing use²³. The fine print is strict: adults only, never on broken skin, and no more than 10 days of use².

Fourteen years earlier, the U.S. Food and Drug Administration (FDA) had moved the other way. In July 2001, it urged companies to pull comfrey supplements off the market and tell customers to stop using them⁴.

Comfrey contains pyrrolizidine alkaloids, compounds that damage the liver⁴. Doctors had linked comfrey tea to hepatic veno-occlusive disease, in which small veins inside the liver become blocked¹.

Same plant, two verdicts. Tradition was close to right about the skin and blind to what regular comfrey tea or pills could do to a liver.

That split is this article’s story. Long use is real information, and it deserves respect. It just answers some questions far better than others. Here is how to tell which is which.

Three countries license remedies on tradition, and each draws a line

Some regulators treat long use as a form of evidence, as long as the product is low risk.

The European Union. Since a 2004 directive, an herbal medicine can earn a “traditional use registration”⁵. It needs at least 30 years of medicinal use, including 15 years inside the EU⁵. No clinical trials of safety or effectiveness are required. Regulators ask instead whether safety data are sufficient and whether a benefit is plausible, given the long use⁵. These products must be meant for use without a doctor’s supervision, and they can’t be injected⁵.

A second route, called “well-established use,” asks for more. The herb needs at least 10 years of medicinal use in the EU, plus published science showing that it works and is acceptably safe⁵. Both routes still demand proof of quality and good manufacturing⁵.

Tradition is the busier road. By the end of 2016, EU countries had granted 1,719 traditional registrations⁶. Well-established use approvals numbered about 800 to 860; the report’s own charts and tables disagree⁶. Devil’s claw root topped the single-herb traditional list, while ivy leaf and ginkgo leaf led the evidence-based list⁶.

Canada. Health Canada lets licensed natural health products carry traditional claims⁷. It asks for at least two generations of safe use, backed by a recognized pharmacopoeia (an official reference book of medicines) or by two independent, authoritative references⁷. The claim has to name its system, such as “traditionally used in Ayurvedic medicine”⁷.

Canada also spells out what tradition can’t support. Traditional claims can’t cover serious diseases, meaning those that need a doctor’s care or can become life-threatening, such as diabetes⁷. They can’t cover conditions the tradition had no way to diagnose, such as high cholesterol, or drug-like actions such as stimulating the immune system⁷. And a history of use, Health Canada says, can’t cancel out a risk that modern science has found⁷.

Australia. The Therapeutic Goods Administration (TGA) accepts traditional claims when a substance’s medicinal use meets or exceeds three generations, or 75 years, and the culture behind that tradition must be identified⁸. Its 2014 evidence guidelines, now marked as a historical document, required each traditional claim to name its tradition, as in “Traditionally used in Western herbal medicine”⁹. Those guidelines also noted that the TGA didn’t evaluate these lower-risk “listed” medicines before they went on sale⁹.

The united states. There is no traditional-use pathway. Most herbs are sold as dietary supplements, and the FDA has no authority to check them for safety or effectiveness before they go on sale¹⁰. Our article on what herbalism is explains the law behind that.

Region	History required	Trials required for traditional claims?	Notable limits
European Union	30 years, 15 in the EU	No; safety data plus a plausible benefit	For use without a doctor’s supervision; no injections5
Canada	Two generations	No	Must name the tradition; no serious diseases or conditions the tradition couldn’t diagnose7
Australia	Three generations (75 years)	No	Must identify the tradition’s culture8
United States	No traditional pathway	No pre-sale review of supplements	FDA can’t check safety or effectiveness before sale10

Notice what the three licensing systems share. They trust tradition for mild problems that people can judge for themselves, and they keep it away from serious disease.

Tradition is a powerful search engine for useful plants

Long use isn’t guesswork. Generations of people noticed what settled a stomach, eased a cough or soothed a burn, and passed it on.

Drug hunters have profited from that. In 2001, pharmacognosists Daniel Fabricant and Norman Farnsworth counted 122 plant compounds approved around the world as single-ingredient medicines, drawn from 94 plants¹¹. (Pharmacognosy is the study of medicines from natural sources.) At least 80% of those compounds traced back to a plant’s traditional medical use, according to a 2002 summary by Geoffrey Cordell of the University of Illinois at Chicago¹¹.

Tradition also keeps details a lab might miss: which part of the plant to use, when to harvest it, how to prepare it and who should avoid it. Our articles on traditional knowledge and on plant-derived medicines tell the famous discovery stories.

Tradition is best at one kind of observation. It catches effects that show up quickly and that people can feel: a calmer stomach, an easier cough, relief by morning. Health Canada’s rules reflect the same idea. A tradition can speak to what its healers could observe, not to a condition they had no way to measure⁷.

Tradition misses harms that are rare, slow or silent

That strength has a mirror-image weakness. If a remedy harms one user in thousands, or causes damage that surfaces months later, no single healer may ever connect the two. The harm can look like an ordinary illness.

Comfrey fits that pattern. Its alkaloids were firmly established as liver toxins in animal studies, and outbreaks of liver vein blockage had been reported in other countries, the FDA wrote in 2001⁴. In people, published case reports tied comfrey tea to the same liver disease¹.

The FDA concluded that supplements containing comfrey were adulterated, meaning unlawful to sell, under federal law⁴. It also asked that liver problems tied to comfrey be reported to MedWatch, its safety reporting program⁴.

Europe’s comfrey cream decision rests on the same science. The European Medicines Agency (EMA) says the alkaloids harm the liver when swallowed, but it expects no significant risk from brief use on the skin³. Even so, a 2024 update to its monograph caps how much of the alkaloids a day’s use may deliver².

Comfrey isn’t alone. Aristolochia herbs, once part of some traditional Chinese formulas, are a darker example; our article on traditional knowledge explains how their slow kidney damage came to light. Kava, a drink used in Pacific Island ceremonies for thousands of years, has been tied to rare liver injury¹⁴. Our article on telling cultural health stories explains why its context matters.

Tradition has a second blind spot: it can’t separate a remedy from everything around it. Colds end on their own, symptoms come and go, and a caring healer can make anyone feel better for a while. Only a fair comparison, usually against a placebo, can pull those apart, as our article on placebos explains.

A cup of tea doesn’t tell you the dose of a capsule

A tradition knows its own preparations. It doesn’t automatically know the new ones.

Green tea is the clearest example. In 2018, the European Food Safety Authority (EFSA) judged catechins, tea’s main active compounds, generally safe when they come from traditionally brewed tea¹². But in trials, supplements supplying 800 milligrams or more a day of EGCG, the leading catechin, were linked to higher liver enzymes, a sign of liver stress¹². EFSA couldn’t name any dose of EGCG from green tea extracts that it considered safe¹².

The EU acted in December 2022. A portion of food made with green tea extract must now hold less than 800 mg of EGCG, and labels must warn against taking 800 mg or more a day¹².

EFSA also saw no sign of a rise in a key liver enzyme among people who drank five or more cups of brewed green tea a day¹². In 2024, the UK’s Committee on Toxicity reviewed the evidence again. It warned that a few sensitive people might still react to extracts below 800 mg a day¹².

The tea-drinking tradition was never wrong. It simply had nothing to say about a concentrated pill. The National Center for Complementary and Integrative Health (NCCIH) makes the broader point: what you buy in a store can be quite different from the version researchers tested¹⁰. It can differ from what a tradition used, too.

Where tradition and trials meet, and where they part

Testing often confirms tradition in a narrower form. Ginger for nausea and peppermint oil for irritable bowel syndrome both have support from controlled trials. Our articles on digestive supplements and on ginger rate the details.

Sometimes the fit is looser. Native Americans used echinacea for respiratory infections, toothaches and snakebites, according to NCCIH¹³. For colds, NCCIH says it may slightly lower your chance of catching one, but it’s still unclear whether it shortens a cold you already have¹³. Our echinacea article walks through the big trials.

Here is how this article’s examples rate.

Use or product	What testing found	Evidence level
Traditional knowledge as a guide to drug plants	Most plant-derived drugs counted in 2001 traced to traditional use11	Strong evidence
Echinacea to lower the chance of catching a cold	May slightly reduce the odds13	Promising but early
Echinacea to shorten a cold	Still unclear13	Not enough evidence
Comfrey cream for minor sprains and bruises, up to 10 days	Accepted in the EU on long use; a Cochrane review found too little evidence for skin use in back pain12	Not enough evidence
Comfrey taken by mouth	Liver toxins; FDA called comfrey supplements adulterated14	Evidence says no, or unsafe
Green tea extract supplying 800 mg or more of EGCG a day	Raised liver enzymes in trials12	Evidence says no, or unsafe

The tradition-to-evidence ladder: place any herb on it

Use this ladder to sort what you know about an herb from what you hope. Each rung adds something the rung below can’t provide.

1. Traditional use only. A named tradition used this plant, part and preparation for this purpose. It tells you the herb is worth a look. It can’t tell you the size of the benefit, the dose of a new form or rare harms.
2. Lab and animal studies. Researchers found a plausible way the herb could act, or an early warning sign. Comfrey’s alkaloids were firmly established as liver toxins in animal studies⁴. Animal results often fail to carry over to people.
3. Small human trials. A few dozen or a few hundred people tried it under controlled conditions. You learn about common side effects and a possible benefit. Results may not repeat.
4. Good reviews of several trials. Pooled studies show whether a benefit is consistent and how large it is. Rare or delayed harms can still hide, because they need years of reports to surface.
5. Regulator recognition based on evidence. Examples include the EU’s well-established use status⁵ and FDA drug approval. A license based on tradition in Europe, Canada or Australia sits on rung 1, however official it looks⁵⁷.

Safety climbs a separate ladder made of case reports, poison center data and warnings. An herb can stand high on the benefit ladder and still carry a safety flag.

Worksheet: where does your herb stand?

• Plant, part and preparation: __
• Tradition, and what it used the herb for: __
• Is your product the same part and form the tradition used? Yes / No
• Is your goal the same as the tradition’s goal? Yes / No
• Highest rung reached for your goal: 1 2 3 4 5
• Safety flags from the FDA, EMA, NCCIH or the NIH LiverTox database: __
• Your situation: pregnant or nursing, a child, liver disease, prescription medicines, upcoming surgery? __
• Decision: try it for a mild problem, ask a clinician first, or skip it

A simple rule follows. The lower the rung, the milder the problem should be. Comfrey cream for a minor bruise on unbroken skin is a rung 1 choice for a low-stakes problem². Comfrey tea gets “skip it” from the safety ladder, whatever its history⁴.

Respecting a tradition means testing it, and asking first

Many people turn to herbs because they trust the wisdom of grandmothers, healers and whole cultures. That trust has earned its place. A tradition is generations of people paying close attention.

Taking that wisdom seriously means asking it the hard questions you would ask a drug company: which plant, which part, how much, and what happened to the people it didn’t help. Asking is not an insult. It’s how comfrey cream kept its place and comfrey pills lost theirs.

Context matters too. Health Canada’s sample wording keeps a claim inside its own system, such as a Traditional Chinese Medicine claim about replenishing Qi, or vital energy⁷. That honors the tradition’s language without dressing it up as modern science.

Respect also means consent. Some Indigenous knowledge is sacred, or belongs to a community that hasn’t offered to share it. Our article on Two-Eyed Seeing, a Mi’kmaw guiding principle, shows how tradition and science can work side by side without one swallowing the other.

When to get help. Talk with a clinician before using an herb if you are pregnant or nursing, are choosing a remedy for a child, or have surgery coming up¹⁰. Do the same if you take prescription medicines or have liver disease.

Never use a traditional remedy in place of care for a serious illness; even Health Canada bars traditional claims for serious diseases⁷. If an herb seems to cause a problem, stop it, call your clinician, and report it to the FDA’s MedWatch program⁴.

Questions readers ask

The bottom line

Long use is real evidence about plants people found helpful, and it has guided scientists to many of medicine’s most important drugs. Regulators in Europe, Canada and Australia trust it for mild, self-limited problems, within firm limits.

What tradition can’t do is spot rare or slow harms, set the dose of a new extract, or measure how much a remedy helps beyond time and care. Use tradition to choose what’s worth trying, testing to decide what’s worth keeping, and a clinician whenever the stakes rise.

Related reading

• Mi’kmaw elders offer a better way to bring tradition and science together
• An ancient recipe led to a Nobel prize, and new treaties ask who benefits
• Herbal supplements are a $13 billion business, and herbalists need no license
• Ginger earns its place for nausea, while its other promises are smaller
• Echinacea came from the prairie and barely touched colds in big trials

Sources

1. Memorial Sloan Kettering Cancer Center. “Comfrey.” About Herbs, Integrative Medicine Service, last updated July 8, 2022. mskcc.org
2. European Medicines Agency, Committee on Herbal Medicinal Products. “European Union herbal monograph on Symphytum officinale L., radix.” EMA/HMPC/572846/2009 Corr1, adopted May 5, 2015, last revised January 31, 2024. ema.europa.eu
3. European Medicines Agency. “Symphyti radix: herbal medicinal product” (summary for the public). EMA, 2015. ema.europa.eu
4. U.S. Food and Drug Administration, Office of Nutritional Products, Labeling and Dietary Supplements. Letter to industry advising removal of comfrey products from the market, July 6, 2001 (copy hosted by e-lactancia.org). e-lactancia.org
5. European Medicines Agency. “Herbal medicinal products.” Regulatory overview, accessed October 2026. ema.europa.eu
6. European Medicines Agency, Committee on Herbal Medicinal Products. “Uptake of the traditional use registration scheme and implementation of the provisions of Directive 2004/24/EC in EU Member States.” EMA/HMPC/322570/2011 Rev. 7, April 18, 2017. ema.europa.eu
7. Health Canada. “Pathway for Licensing Natural Health Products used as Traditional Medicines.” Guidance document, last modified July 6, 2022. canada.ca
8. Therapeutic Goods Administration (Australia). “Using literature based submissions for listed, assessed listed and registered complementary medicines.” TGA, accessed October 2026. tga.gov.au
9. Therapeutic Goods Administration (Australia). “Evidence guidelines: Guidelines on the evidence required to support indications for listed complementary medicines.” Version 2.1, July 2014 (historical document). tga.gov.au
10. National Center for Complementary and Integrative Health. “Using Dietary Supplements Wisely.” NIH, last updated January 2019, accessed October 2026. nccih.nih.gov
11. Cordell GA. “Discovering Our Gifts from Nature, Now and in the Future, Part I.” Revista de Química, Pontificia Universidad Católica del Perú, December 2002 (summarizing Fabricant DS, Farnsworth NR, Environmental Health Perspectives, 2001). revistas.pucp.edu.pe
12. UK Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment. “Statement on the Hepatotoxicity of Green Tea Catechins.” COT Statement 08/2024, November 2024.
13. National Center for Complementary and Integrative Health. “Echinacea.” NIH, last updated November 2024. nccih.nih.gov
14. National Center for Complementary and Integrative Health. “Kava.” NIH, last updated April 2025. nccih.nih.gov