Comfrey (oral)

What is Comfrey (oral)?

Comfrey (Symphytum officinale) is a perennial herb in the borage family that has been used traditionally for centuries to treat wounds, bruises, and inflammatory conditions. While topical comfrey preparations remain available in some regions, oral comfrey supplements have been banned or heavily restricted in many countries including the United States, Canada, Australia, and much of Europe due to serious safety concerns.

The plant contains pyrrolizidine alkaloids (PAs), particularly symphytine and echimidine, which are hepatotoxic compounds that can cause severe liver damage and potentially fatal liver failure. Despite its historical use in folk medicine for treating digestive issues, respiratory problems, and promoting bone healing, the oral consumption of comfrey is now considered dangerous by major health regulatory agencies worldwide.

Health benefits & uses

Limited evidence: Historically, oral comfrey was used to treat peptic ulcers, gastritis, inflammatory bowel conditions, and respiratory ailments. Some traditional practitioners claimed it could accelerate bone healing and reduce internal inflammation. However, due to the severe safety risks associated with pyrrolizidine alkaloids, no modern clinical trials have been conducted to evaluate these purported benefits for oral consumption.

The compound allantoin, found in comfrey, does demonstrate wound-healing and anti-inflammatory properties in laboratory studies. However, these benefits do not outweigh the substantial hepatotoxic risks when comfrey is consumed orally, and safer alternatives exist for all claimed therapeutic uses.

How it works

Comfrey’s potential therapeutic effects are primarily attributed to allantoin, a purine derivative that promotes cell proliferation and tissue regeneration. Allantoin may stimulate the growth of healthy tissue and reduce inflammation through its effects on cellular metabolism and wound healing processes.

However, the pyrrolizidine alkaloids present in comfrey are metabolized by the liver into highly reactive compounds called pyrroles. These toxic metabolites bind to cellular proteins and DNA, causing severe hepatocellular damage, liver necrosis, and potentially irreversible hepatic veno-occlusive disease. The liver damage can progress to cirrhosis, liver failure, and death.

Dosage

Oral comfrey is not recommended at any dosage due to safety concerns. No safe level of consumption has been established for comfrey containing pyrrolizidine alkaloids. The FDA has banned the sale of oral comfrey supplements in the United States since 2001.

Some manufacturers have attempted to produce “PA-free” comfrey extracts, but these products cannot be guaranteed to be completely free of toxic alkaloids. Healthcare providers universally advise against the internal use of any comfrey products due to the risk-benefit profile being unacceptably unfavorable.

Food sources

Comfrey is not found in conventional foods. It grows as a wild herb in Europe, Asia, and North America, and some people historically consumed it as a leafy green vegetable or brewed it into teas. However, such consumption is now strongly discouraged.

Young comfrey leaves contain the highest concentrations of pyrrolizidine alkaloids, making them particularly dangerous. Roots also contain significant levels of these toxic compounds. No part of the comfrey plant is considered safe for oral consumption.

Safety & side effects

Oral comfrey consumption can cause severe and potentially fatal adverse effects, including:

• Hepatotoxicity and liver failure
• Hepatic veno-occlusive disease
• Liver cirrhosis
• Pulmonary hypertension
• Pneumonia
• Death

These serious adverse effects have been documented even with short-term use and relatively small amounts. The toxic effects may be delayed, with liver damage becoming apparent weeks to months after consumption. There is no known antidote for pyrrolizidine alkaloid poisoning, and liver damage may be irreversible.

Interactions

Oral comfrey may interact dangerously with:

• Hepatotoxic medications: Any drugs that can cause liver damage may have additive toxic effects when combined with comfrey
• Alcohol: May increase the risk of liver damage
• Other pyrrolizidine alkaloid-containing herbs: Including coltsfoot, borage, and certain Senecio species, may increase toxicity risk

Due to the severe hepatotoxicity risk, comfrey should not be used with any medications or substances, as liver damage could impair the body’s ability to metabolize other compounds safely.

Who should be cautious

Everyone should avoid oral comfrey consumption. Particularly vulnerable populations include:

• Pregnant and breastfeeding women
• Children and adolescents
• Individuals with existing liver disease
• People taking hepatotoxic medications
• Those with a history of alcohol abuse
• Individuals with compromised immune systems

No population has been identified for whom oral comfrey use would be considered safe or appropriate.

Frequently asked questions

Is topical comfrey safer than oral comfrey?

Topical comfrey preparations may have a better safety profile than oral forms, as systemic absorption is limited. However, even topical use should be restricted to intact skin, avoided on open wounds, and limited in duration. Always consult healthcare providers before using any comfrey products.

Are there PA-free comfrey products available?

Some manufacturers claim to produce pyrrolizidine alkaloid-free comfrey extracts, but the reliability and safety of these products remain questionable. Most health authorities recommend avoiding all comfrey products for internal use, regardless of claimed PA content.

What should I do if I’ve consumed comfrey?

If you have consumed comfrey, especially regularly or in large amounts, consult a healthcare provider immediately. Liver function tests may be necessary to assess for hepatotoxicity, and monitoring may be required even if no immediate symptoms are present.

Are there safer alternatives to oral comfrey?

Yes, numerous safer alternatives exist for the conditions comfrey was traditionally used to treat. For wound healing and inflammation, consider turmeric, aloe vera (topical), or conventional anti-inflammatory medications under medical supervision.

Why was comfrey banned if it was used historically?

Historical use doesn’t guarantee safety. Modern toxicological studies revealed the severe hepatotoxic potential of pyrrolizidine alkaloids in comfrey, leading regulatory agencies to ban oral preparations to protect public health. Many traditional remedies have been found to be unsafe when subjected to rigorous scientific evaluation.