Understanding the Risks: What is Comfrey Tea High In?

October 26, 2025 •

4 min read

Scientific studies have identified that comfrey, and therefore comfrey tea, contains toxic compounds known as pyrrolizidine alkaloids (PAs), which are highly dangerous to human health. This is a critical piece of information for anyone investigating 'what is comfrey tea high in?' as a dietary supplement. While historically used as a folk remedy, modern health agencies warn against oral consumption due to the severe risk of liver damage.

Quick Summary

Comfrey tea is rich in toxic pyrrolizidine alkaloids that can cause irreversible liver damage and cancer when ingested by humans, leading health authorities to ban or restrict its oral use. It is also high in plant nutrients like potassium, calcium, and nitrogen, making it a powerful natural fertilizer for gardens.

Key Points

High in Pyrrolizidine Alkaloids (PAs): Comfrey tea contains toxic compounds called PAs, which are extremely harmful to human health and can cause severe liver damage and cancer.
Not for Human Consumption: Due to its PA content, health agencies like the US FDA and Health Canada strongly advise against and have restricted the oral ingestion of comfrey tea.
Excellent Plant Fertilizer: The leaves are high in potassium, nitrogen, and other minerals, making comfrey tea a potent, organic liquid fertilizer for gardening purposes.
Risk of Veno-occlusive Disease: Oral intake of comfrey can cause veno-occlusive disease, a serious condition where liver veins are blocked, potentially leading to liver failure.
Safe for Topical Use (with caution): Small, limited topical applications on unbroken skin are considered possibly safe for short durations, but should not be used on broken skin or ingested.
Traditional Use Disproven: While once used internally in folk medicine, modern toxicology has revealed the severe dangers of this practice.

The Dual Nature of Comfrey: Nutrients and Toxins

Comfrey (Symphytum officinale) is an herbal plant with a centuries-old history of medicinal use, earning it nicknames like 'knitbone' for its perceived ability to heal wounds and fractures. However, modern scientific analysis has revealed a critical and dangerous duality: while it contains some beneficial compounds, it is also alarmingly high in potent toxins. Understanding this dual nature is crucial, especially for anyone considering comfrey tea for consumption.

The Dangerous Pyrrolizidine Alkaloids

When examining what is comfrey tea high in, the most important components are a group of chemical compounds called pyrrolizidine alkaloids (PAs). These natural toxins are highly dangerous when ingested by humans and animals. In the liver, PAs are metabolized into highly reactive pyrrole metabolites, which can damage the delicate hepatic endothelial cells and block small veins. This condition, known as veno-occlusive disease, can progress to liver failure and is potentially fatal. The concentration of PAs varies depending on the plant species, age, and part used, with roots typically containing higher levels than leaves.

The Nutritional Components (For Plants)

On the other side of its chemical profile, comfrey is indeed rich in many nutrients, but these are primarily of interest to gardeners and farmers. Comfrey has deep taproots that draw a large quantity of minerals from deep within the soil. As a result, its leaves are notably high in:

Potassium (K): Crucial for flowering and fruiting plants, such as tomatoes and peppers.
Nitrogen (N): Essential for lush, leafy growth.
Calcium (Ca): Supports strong cell walls in plants.
Other Trace Minerals: Including magnesium, iron, and manganese.

When comfrey leaves are fermented in water, they create a nutrient-rich liquid manure or 'tea' that is excellent for fertilizing plants. However, this use for plants is completely separate from any consideration of human consumption.

Why Oral Consumption is a Major Health Risk

Due to its high concentration of liver-toxic PAs, health authorities worldwide have restricted or banned the oral consumption of comfrey products. This is a reversal of its traditional use, which occurred before the risks of PAs were fully understood.

Health Agency Warnings and Bans

US FDA: Has recommended the removal of all oral comfrey products from the market.
Health Canada: Advises Canadians not to ingest any health product containing comfrey due to the risk of liver damage.
Other Countries: Many other nations have followed suit, recognizing the severe and irreversible harm caused by ingesting PAs.

Veno-occlusive Disease and Other Harm

Ingesting comfrey can lead to serious health complications, with veno-occlusive disease (VOD) being the most well-documented. Symptoms of VOD can include jaundice (yellowing of the skin), abdominal pain, and fluid retention (ascites). In addition, animal studies have shown that comfrey and its PAs can be carcinogenic, meaning they can cause cancer. The risk is present even in low doses over an extended period.

Safe Use of Comfrey: The Garden's Powerhouse

Since oral consumption is unsafe, the primary modern application of comfrey is in gardening. Its nutrient-rich leaves make it a fantastic natural resource for cultivating a healthy garden without synthetic fertilizers.

Here are some of comfrey's safe uses in the garden:

Liquid Fertilizer: Steeping comfrey leaves in water creates a powerful liquid feed, high in potassium and nitrogen, perfect for fruit and vegetable plants.
Mulch: Layering fresh or wilted comfrey leaves around the base of plants releases nutrients into the soil as they decompose.
Compost Activator: Adding comfrey leaves to a compost pile accelerates decomposition due to their high nitrogen content.
Green Manure: Chopping comfrey and digging it directly into the soil enriches it with minerals.

Comparing Comfrey Tea to a Safe Herbal Tea

To highlight the crucial difference between comfrey tea for garden use and a safe herbal tea for human consumption, consider the following comparison:


Feature	Comfrey Tea (For Garden Use)	Chamomile Tea (For Human Consumption)
Primary Purpose	Fertilizer for plants	Soothing beverage for humans
High In	Potassium, nitrogen, calcium	Antioxidants, anti-inflammatory compounds
Oral Safety	Not safe for human consumption; toxic to liver.	Generally regarded as safe for oral consumption.
Toxic Components	High concentration of liver-toxic pyrrolizidine alkaloids (PAs).	No known toxic alkaloids.
Main Risks	Severe liver damage (veno-occlusive disease), cancer.	Allergic reactions in sensitive individuals, primarily to pollen.
Typical Use	Diluted and applied to soil or foliage.	Steeped in hot water and consumed as a drink.

Conclusion: Prioritizing Safety in Nutrition

In summary, when asking what is comfrey tea high in, the answer is twofold: it is high in beneficial plant nutrients like potassium and nitrogen, but also dangerously high in liver-toxic pyrrolizidine alkaloids. While its use as a garden fertilizer is safe and effective, consuming comfrey tea is an extremely high-risk activity that can cause serious and irreversible liver damage. The widespread bans and warnings from health organizations emphasize that this is a risk not worth taking. Anyone seeking a nutritive beverage should instead turn to the many safe and beneficial herbal teas available. The historical use of comfrey is a clear example of how traditional practices can be disproven by modern scientific understanding, prioritizing safety in nutrition above all else.

For more information on the liver toxicity of comfrey, refer to the National Institutes of Health's LiverTox resource.

Frequently Asked Questions

Comfrey tea is dangerous for humans because it contains toxic compounds called pyrrolizidine alkaloids (PAs). These compounds are metabolized in the liver into substances that cause irreparable liver damage, including veno-occlusive disease, and can be carcinogenic.

Comfrey has very deep taproots that pull nutrients like potassium and nitrogen from deep within the soil, where they are typically unavailable to other plants. These nutrients are then stored in its leaves, making the plant itself high in these minerals, which can be extracted for use as a plant fertilizer.

No, it is possibly unsafe to use comfrey tea or other comfrey products on broken or damaged skin. The toxic PAs can be absorbed through the skin, exposing the body to harmful compounds.

The primary modern use of comfrey is for gardening. Its nutrient-rich leaves are fermented to create a liquid fertilizer or are used as mulch to enrich the soil. It is also known to be an excellent compost activator due to its high nitrogen content.

Pyrrolizidine alkaloids are an intrinsic component of the comfrey plant and cannot be removed by simply making a tea or through typical preparation methods. Specialized genetic editing techniques have been explored to create PA-free comfrey, but this is not available for general consumption.

Comfrey tea is a potent, non-consumable liquid used to fertilize plants, not for human consumption, due to its toxicity. Herbal teas for humans, such as chamomile or mint, are made from safe, non-toxic plants and are intended for drinking.

No, while comfrey was historically used as a folk remedy, its risks were not fully understood in the past. Modern scientific advances in toxicology have uncovered the severe liver-damaging and carcinogenic properties of pyrrolizidine alkaloids, leading to current restrictions and warnings against oral use.