Comfrey (Symphytum officinale): Uses, Evidence and Safety

Do not swallow comfrey, in any form, and do not give it to children. Comfrey contains pyrrolizidine alkaloids, which EMA says have toxic effects on the liver when taken by mouth. [1] In 2001 the US Food and Drug Administration (FDA) asked supplement makers to stop marketing products containing comfrey because of a serious hazard when ingested. [2] Signs of liver trouble such as tiredness, dark urine, or yellow skin or eyes call for medical help; see liver safety and supplements. If someone swallowed comfrey or a plant thought to be comfrey, call Poison Help at 1-800-222-1222 (US) or 911; other countries are on Poison Help by Country.

Overview

Memorial Sloan Kettering describes comfrey as a fast-growing plant whose leaves and roots have been used historically for wound healing and other conditions. [3] This page covers comfrey as a herb product; it gives no preparation instructions and does not teach how to find or recognize the plant. Memorial Sloan Kettering says comfrey has been confused with foxglove, a poisonous plant with similar leaves, and that several cases of accidental poisoning occurred when what was thought to be comfrey tea was swallowed. [3] Do not rely on a photo or app to identify plants; see plant and mushroom poisoning. The pyrrolizidine alkaloid family is explained on pyrrolizidine alkaloids: comfrey, coltsfoot and borage.

Scientific name, plant part and family

Symphytum officinale L. (common comfrey), family Boraginaceae, is the accepted name. [4] EMA says comfrey root is the root of Symphytum officinale. [1] The FDA letter names three species: common comfrey (S. officinale), prickly comfrey (S. asperum) and Russian comfrey (S. x uplandicum). [2] A Canadian Forces fact sheet (2016) says two comfrey species contain pyrrolizidine alkaloids that damage the liver, that echimidine is found in prickly and Russian comfrey, and that not all manufacturers identify the species, so Health Canada has advised Canadians to avoid all of these products. [5]

Traditional use

This is tradition, not proof. The Canadian fact sheet says comfrey roots and leaves have been used for centuries for healing properties, historically believed to help heal broken bones and wounds. [5] The EU committee accepted a specific comfrey root ointment for symptoms of minor sprains and bruises based on traditional use of at least 30 years. [1]

What research shows

These results are for particular standardized gels or ointments. Homemade or other products are not covered by them.

Forms and why the form matters

The EU assessment covers only a specific ethanol extract in creams or ointments for the skin. [1] It says the amount of pyrrolizidine alkaloids must be specified in each product. [1] In animals, pyrrolizidine alkaloids are hepatotoxic after oral administration, and in rats some have caused tumors. [8] A 2022 laboratory study with human skin found low penetration of three pyrrolizidine alkaloids through skin, which helps regulators assess skin products; it was a lab model, not a study in people. [9] No tea, capsule or other oral preparation is covered here.

Safety

• Liver and cancer concerns: the FDA letter says pyrrolizidine alkaloids are firmly established hepatotoxins in animals, that outbreaks of hepatic veno-occlusive disease have been reported elsewhere and the toxicity in humans is generally accepted. [2] Memorial Sloan Kettering says cases of liver toxicity have been reported and that animal experiments suggest liver cancer. [3]
• Regulators: FDA (United States, July 2001): firms should stop marketing supplements containing comfrey. [2] Health Canada (as quoted in a 2016 Canadian Forces fact sheet): avoid these products until species are identified. [5] Memorial Sloan Kettering also states comfrey is prohibited in Australia and New Zealand; we did not read those regulators directly. [3]
• Skin products (EU): the monograph says no significant risk is expected for short skin use, limits use to 10 days, and says not to apply to broken or irritated skin, eyes or mucous membranes. [8] [1] EMA states a limit on alkaloid exposure per day; the 2015 public summary gives 0.35 microgram and the 2024 monograph below 1 microgram, so check the current figure with a pharmacist. [1] [8]
• Medicines: the EU monograph lists interactions as none reported. [8] See how interactions work.
• Pregnancy and breastfeeding: use is not recommended; pyrrolizidine alkaloids from the plant have shown reproductive toxicity in animals. [8] See pregnancy and breastfeeding.
• Children: under 18, use has not been established. [8]
• Before surgery, kidney, allergy: not described in the sources we read. Tell the surgical team about all products.

Quality notes

The Canadian fact sheet says not all manufacturers identify the species of comfrey in their products. [5] See adulteration and substitution of herbs.

Official statements

• FDA (United States, 2001): comfrey in dietary supplements is a serious concern. [2]
• EMA/HMPC (European Union, summary 2015, monograph 2024): traditional use of a specific skin ointment for minor sprains and bruises, adults, up to 10 days. [1] [8]

A clinician or pharmacist decides what is right for a particular person.