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Lat updated July 31, 2016 (originally published August 21, 2013)

By Louise Carr, Associate Editor and featured Columnist

[Health and fitness articles are reviewed by our team of Doctors and
Registered Nurses and other members of our Editorial Board]

Using comfrey for a bruise or a sprain stops the swelling,
and sipping comfrey tea is good for diarrhea. Because
natural is always better, right?

Comfrey, a leafy green plant, has been used for centuries
as a medicine and as animal feed. It’s easy to believe that a
traditional plant will benefit your health, not harm it. But
did you know this natural healer has an FDA warning
attached to it? And that ingesting comfrey has been
associated with severe
liver damage and even death?

Taking comfrey orally for as little as 19 days has resulted in
severe liver damage (
for children suffer in as little as five

Comfrey doesn’t seem so benign now. What exactly are the
dangers associated with comfrey? Is there a safe dose?
How can comfrey damage your health?

What Is Comfrey Used For?

Comfrey is native to Europe and Asia and is one of the
oldest plants known to humans. From the genus
Symphytum, comfrey was cultivated by the ancient Romans
and Egyptians  starting around 400 B.C., according to a
1992 paper led by Dr. T.M. Teynor of the  Center for
Alternative Plant and Animal Products, University of

Comfrey was traditionally used, without questioning its
safety, to help bones heal, treat sprains, reduce swelling,
treat minor wounds and ease the pain of bruises. Comfrey
is still included in creams that heal the skin along with
herbs such as calendula and aloe.

Comfrey was also taken orally for digestive problems,
including diarrhea and stomach upset, and lung conditions.
The plant is also said to be useful as a mouthwash for sore

However, the benefits of comfrey stack up against a big
problem – comfrey may present a serious health hazard
because it is associated with liver damage.

FDA Warning on Comfrey

The Food and Drug Administration issued a warning in July
2001 about comfrey. The warning was addressed to
dietary supplement manufacturers, who were advised to
remove comfrey products from the market.

“These plants,” says the FDA, “are a source of pyrrolizidine
alkaloids that present a serious health hazard to consumers
when they are ingested.”

The use of comfrey in supplements is a serious concern to
the FDA and in the warning the Administration
recommended that firms making a product containing
comfrey should remove it from the market and alert
consumers to stop using the product, under the Federal
Food, Drug, and Cosmetic Act and the Dietary Supplement
Health and Education Act of 1994.

In addition, the FDA reminded firms that the Federal Trade
Commission has also taken action against the makers of
products that include comfrey.

The use of comfrey in products is restricted in countries
such as the UK and Australia, and banned in Germany and

Dangers of Comfrey

What’s the problem with comfrey? The plant is a concern
because it contains substances called "pyrrolizidine
alkaloids", or "PAs".

Pyrrolizidine alkaloids are clearly linked with a number of
serious health conditions in animals, and have recently
been associated with toxic effects in humans.

Why are PAs dangerous? Pyrrolizidine alkaloids can cause
liver damage, lung damage, and cancer.

Comfrey and Liver Disease

Eating comfrey or drinking comfrey tea can cause liver

The most common form of liver disease associated with
comfrey is veno-occlusive disease, a blockage of small
veins, leading to cirrhosis and liver failure - hepato-
occlusive disease – and the need for a liver transplant.

A 2000 report by the University of Erlangen-Nuernberg,
Germany clearly stated the association of  pyrrolizidine
alkaloids with “substantial toxicity after their ingestion as
tea (with) the use of comfrey leaves recognized as a
substantial health hazard with hepatic toxicity in humans
and carcinogenic potential in rodents.”

In 2002, doctors in South Africa identified pyrrolizidine
alkaloids as the cause of death for a 3 and 1/2 month old
child who had been given a traditional herbal remedy for a
week. The child suffered from fatal liver disease and the
confirmed diagnosis after was comfrey posioning.

If you have taken comfrey and experience nausea,
vomiting, unusual fatigue, abdominal pain, yellow skin or
eyes, dark urine, itching and loss of appetite, notify your
doctor immediately as these can be signs of early liver

How Many Fatalities Are Associated with Comfrey?

The ingestion of comfrey has been linked with at least two
deaths, and many severe side effects. A 1990 study from
the Auckland Hospital, New Zealand showed how a 23-year-
old man died from liver disease after consuming comfrey
leaves. An unpublished report to the USP Practitioners
Reporting Network listed a death from liver damage of a
man after drinking comfrey tea.

A 13-year-old boy experienced veno-occlusive disease after
taking comfrey over two to three years as an inflammatory
bowel disease treatment, according to a 1987 study from
the University Department of Medicine, Bristol Royal
Infirmary, UK.  

A newborn infant also suffered – after the mother ingested
comfrey in tea (1988, Centre Hospitalier Universitaire
Vaudois, University of Lausanne, Switzerland.) And a 49-
year-old woman suffered veno-occlusive disease after
taking comfrey pills and drinking comfrey tea over four

Comfrey Is a Carcinogen?

Pyrrolizidine alkaloids are associated with cancer and
genetic mutations, according to Trease and Evans'
Pharmacognosy, 14th ed. Philadelphia: Saunders; 1998.
Comfrey has been tested on rats and these studies show
that the supplement has a toxic effect that may lead to
genetic mutations that cause cancer.

In a 2005 study from the US Food and Drug Administration
published in the British Journal of Cancer pyrrolizidine
alkaloids helped cause mutational defects in the liver.

Is There a Safe Way to Use Comfrey?

Drinking comfrey in a tea or taking comfrey pills may cause
toxic effects in as few as five to seven days in a child and
19 to 45 days in an adult, according to the Natural
Medicines Comprehensive Database Consumer Version, so
there really is no “safe” oral dose of comfrey. Very low
doses taken orally have been shown to cause harm,
according to a 1988 study from the Department of
Community Services and Health, Canberra, Australia.

When it comes to comfrey creams and lotions, the
pyrrolizidine alkaloids are poorly absorbed through the skin
so are considered safe to use topically by some experts –
but they are absorbed to some extent. What’s more,
comfrey is dangerous if applied to broken skin. The Federal
Trade Commission prohibits the use of comfrey-containing
products intended for internal use and for use on open

The roots of the comfrey plant have 10 times more
pyrrolizidine alkaloids than the leaves. And steer clear of
“prickly comfrey” (Symphytum asperum) or “Russian
comfrey” (Symphytum x uplandicum) as these species are
particularly toxic – sometimes these are mistakenly
marketed as ordinary, safer, comfrey.

It is difficult to know exactly how much of the dangerous
pyrrolizidine alkaloids you are ingesting when you drink
comfrey tea, or putting into your body through use on the
skin, so it is safer to avoid it altogether. If you do use it,
don’t apply comfrey cream for more than four to six weeks
in a year, or use it for more than 10 days in a row.
Pregnant and nursing women, and children, should
definitely not use comfrey.

Natural products can be of huge benefit to your health and
minimize the side effects often caused by chemical
medications. But it is important to remember that natural
doesn’t necessarily mean safe – as is the case with
comfrey. Check warnings and consult your doctor if you
want to try something new.


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