I'll get right to the point. Comfrey is like some kind of miracle herb, able to help broken bones mend quickly and heal wounds and alleviate troubling skin conditions in a trice. The only problem is it's toxic to your liver. I will never, ever, use comfrey in any of my herbal preparations.
Comfrey contains pyrrolizidine alkaloids, or PA's, which can be toxic to the liver and can cause liver damage. The FDA prohibits injested forms of comfrey from being sold in the U.S.
Comfrey root contains the highest concentrations of PA's, the next highest concentration is found in new leaves, and the lowest concentration in older leaves.
Comfrey is readily absorbed through the skin, hence the ability of topical preparations to aid in the healing of broken bones, and in the healing of wounds.
Using topical preparations containing comfrey should be done with caution, and only preparations made with comfrey leaves should be used - avoid the roots. And never put topical preparations containing comfrey on broken skin. Children should NEVER use any form of comfrey preparation under any circumstances.
I continue to be amazed at the amount of creams, salves, lotions, sitz bath "teas", etc., that are available which contain comfrey. I have even seen diaper rash creams which contain comfrey root extratives, and skin care salves with comfrey which proclaim to be "safe for the whole family."
I research the herbs I use to make sure they're safe. A lot of people think that because herbs are 'natural' that they are inherently safe. This is wrong. Medicinal herbs work because they contain chemical compounds that react with your body in the same - or a similar - way that manufactured chemical compounds (medicines) react with your body.
There are lots of natural things that are harmful, rattle snakes, hemlock, many types of mushrooms, many types of berries - you wouldn't eat any red berry you came across in the wild, would you? No. Why? Because many of them are poisonous. Even though they're natural.
So what I'm trying to say is, if you use herbal remedies, do your homework. Not everything you can lay your hands on is safe.
Below you can read what the University of Maryland Medical Center says about comfrey, or you can visit their alternative medicines page about comfrey here.
What UMMC has to say:
What's It Made Of?:
Comfrey contains substances that help skin regenerate, including allantoin, rosmarinic acid, and tannins. It also contains poisonous compounds called pyrrolizidine alkaloids.
Oral comfrey products have been banned in the U.S. and many European countries, but topical preparations are still available.
Comfrey ointments (containing 5 - 20% comfrey), creams, poultices, and liniments are made from the fresh or dried herb, leaf, or root of comfrey species. Use only products made from leaves of common comfrey.
Be sure to buy comfrey preparations from established companies with good reputations, and who distribute their products through trustworthy and knowledgeable establishments. Follow dosage recommendations below.
How to Take It:
Never give a child comfrey by mouth, and do not apply creams or ointments containing comfrey to a child's skin.
Never take comfrey by mouth. Severe liver poisoning and even death may occur.
Use herb and leaf ointments, creams, and other topical preparations. Toxic alkaloids can be absorbed through the skin so it's important to follow these safety recommendations:
Never apply comfrey to broken skin.
Use only small amounts of comfrey-containing creams for no longer than 10 days at a time.
Do not use any comfrey product for more than 4 - 6 total weeks in a year.
Comfrey contains toxic substances that can cause severe liver damage and possibly even death. For this reason, comfrey and comfrey-containing products should never be taken orally.
Comfrey contains toxic substances that can be absorbed by the skin, so even topical preparations should be used for only a short time under the supervision of a knowledgeable health care provider.
Comfrey should never be applied to open wounds or broken skin.
Do not use comfrey if you have liver disease, alcoholism, or cancer.
Children, the elderly, and pregnant or breastfeeding women should not use comfrey products -- either orally or topically -- under any circumstances.
There are no known scientific reports of interactions between comfrey and conventional medications. Some herbs that have also been known to cause liver problems, such as kava, scullcap, and valerian, should not be used while using comfrey ointment or cream because of the increased potential for liver damage.