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5 Risky Herbal Supplements

Even though they're natural, some herbal supplements can be dangerous.


Comfrey (Symphytum officinale) has "a well-deserved reputation for healing injured tissues," such as wounds, bruises, sprains, bone fractures, and the swelling and inflammation that can go along with them, Weil tells WebMD. But because of the risk for severe liver and possibly lung damage, "comfrey should never be taken by mouth," Weil says.

The FDA recommended in 2001 that manufacturers remove comfrey products from the market. Still, comfrey is easy to find.

"My local coffee shop serves comfrey tea, and when I told them it was a liver-toxic herb, they said, ‘Oh, we sell a lot of it,'" Fugh-Berman says.

Weil recommends applying comfrey to wounds that don't heal easily, including open bedsores and diabetic ulcers. However, the U.S. Pharmacopeia, a scientific organization that sets standards for dietary supplements, advises against using comfrey on broken skin, as the toxins that may affect the liver can be absorbed.


Chaparral (Larrea divaricata, Larrea tridentata) is said to reduce pain, inflammation, and skin irritation. However, there is little evidence for this, Weil tells WebMD. Chaparral has also been promoted as a cancer-fighting herb, but according to the American Cancer Society, there is no evidence supporting that, either.

Easily found online in many forms, chaparral has been listed in the FDA's poisonous plant database since 1997 because of the risk of severe -- and in some cases, irreversible -- liver damage.

According to the American Cancer Society, chaparral can cause serious drug interactions with some prescription and over-the-counter drugs, including blood thinners; anti-inflammatory drugs, such as aspirin, ibuprofen, and naproxen; diabetes medications, and certain antidepressants.


Pennyroyal (Mentha pulegium) has not been proven effective for any suggested uses. It was traditionally used to cause abortion, but the large doses required for this could kill the mother or cause irreversible damage to the liver and kidneys, according to the National Institutes of Health.

According to the National Institutes of Health, pennyroyal oil is considered unsafe for anyone at any dose, and it is unknown whether the tea is safe.

"It's a mint, and you don't get that much poison in a tea, but I wouldn't risk it. Go for spearmint. Why go for the liver-toxic mint?" Fugh-Berman says.

Listed in the FDA's poisonous plant database in 1997, pennyroyal can be found online in many forms, including oil.

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