Is Comfrey Poisonous? – Pyrrolizidine Alkaloids, Liver Risk, and Safety

Comfrey (Symphytum officinale) is not safe to eat for humans, dogs, or cats. The plant contains pyrrolizidine alkaloids (PAs), compounds that damage the liver with repeated or concentrated oral exposure. Topical comfrey preparations are widely considered lower risk and are permitted in some countries under quantity limits. Ingesting the plant or using it as an oral supplement is a different matter entirely and should be avoided.

What Part of Comfrey Is Toxic?

Pyrrolizidine alkaloids are present throughout the plant but are most concentrated in the roots. The leaves contain lower levels. PAs are hepatotoxic: they damage liver cells and can cause sinusoidal obstruction syndrome, a blockage of small liver veins that can progress to liver failure with repeated exposure.

Comfrey has a long history as a herbal remedy and garden plant. Many topical comfrey creams and ointments are sold legally. Regulatory bodies including the European Medicines Agency restrict oral comfrey preparations because of the PA content, and the FDA has warned against oral use in the United States.

Symptoms of Comfrey Ingestion

The risk is primarily chronic rather than acute. A single small exposure is unlikely to cause obvious symptoms. Repeated ingestion over weeks or months causes cumulative liver damage.

Dogs and cats: Liver toxicity with repeated exposure. Signs include lethargy, loss of appetite, vomiting, abdominal distension from fluid accumulation, and jaundice. Symptoms typically emerge after a pattern of ingestion, not from a single episode. If a pet regularly chews on comfrey in the garden, that represents a genuine risk.

Humans and children: Oral comfrey products have caused hepatic veno-occlusive disease in documented cases. Children are more vulnerable to PA toxicity than adults due to lower body weight. Symptoms of serious liver injury include fatigue, right-sided abdominal pain, and abdominal swelling. Consuming the leaves or roots as food or in tea is the main route of human exposure.

What to Do If Someone Ingests Comfrey

1. If a child ate plant material, note the approximate amount and call poison control at 1-800-222-1222 (US).
2. Do not induce vomiting without professional guidance.
3. For pets, contact your vet or the ASPCA Animal Poison Control Center at 888-426-4435.
4. If using a comfrey supplement or herbal product, check the label for PA content and contact poison control if uncertain about dose or safety.
5. For repeated exposure, request a liver function test from a physician or vet rather than waiting for symptoms.

A single small exposure is unlikely to cause lasting harm, but a call to poison control to confirm is worthwhile. Repeated exposure deserves professional evaluation.

Safe Handling

• Do not allow pets to graze on comfrey in the garden. Fence off or remove accessible plants.
• Keep dried comfrey and any herbal preparations out of reach of children and pets.
• Topical creams and gels are generally lower risk but should still be stored safely.
• Do not use comfrey in teas, tinctures, or as a food ingredient.
• Do not apply comfrey preparations to open wounds or broken skin even topically.

Frequently Asked Questions

Is topical comfrey safe? Topical comfrey products are regulated but permitted in many regions for short-term use on intact skin. The liver toxicity concern associated with oral PAs does not apply at the same level to limited skin absorption. Follow product guidelines and keep products away from children.

Is comfrey safe for horses or livestock? No. Pyrrolizidine alkaloid toxicity is well documented in livestock. Horses, cattle, and sheep have developed severe liver disease from grazing on PA-containing plants. Comfrey should not be accessible to grazing animals.

My pet ate one comfrey leaf. Should I worry? A single small exposure is unlikely to cause lasting liver damage, but calling your vet is reasonable to confirm based on your pet’s size and the amount eaten.

Is garden comfrey the same as the herbal remedy sold in stores? Yes. Symphytum officinale is the same species used in commercial herbal preparations. All parts of the garden plant carry the same PA risk.