Even today, years after pyrrolizidine alkaloids were found and identified in Comfrey (aka Symphytum officinale), herbalists continue to recommend its use. A few years ago, after I had commented on an online site about the dangers of using Comfrey, a well-known animal herbalist called me on the phone. “Comfrey isn’t dangerous”, she told me. “It is just a scam by Big Pharma to stop us using it so that they can make more money.”
It isn’t a scam by Big Pharma. Comfrey can kill. Pyrrolizidine alkaloids are very toxic to the liver and are also carcinogenic (cause cancer). The way that they work is by blocking small blood vessels in the liver. This leads to cirrhosis and eventually liver failure. In humans, use of comfrey for as little as 5 days (in children) or 19 days (in adults) has resulted in severe liver damage and death. Even long term use of very small doses can be harmful, as the damage is cumulative and the damage is irreversible.
Generally speaking, the root has higher levels of these molecules than the leaves. Also, some of Symphytum officinale’s close relatives (commonly mistaken for Comfrey) have even higher levels.
What about topical (skin) use? Pyrrolizidine alkaloids can be absorbed through the skin as well. So, if you’re going to use a cream or ointment, make sure that the daily amount applied to the skin doesn’t exceed 100 micrograms. You might find that it is difficult to ascertain the correct level as most preparations don’t put the amount onto the label. Also, the analytical method used to assay these compounds is a bit unreliable.
Both the leaves and the roots of Comfrey have been shown to cause cancer. Rats fed Comfrey (0.5% roots and 8% leaves) developed hepatomas (liver cancer) and died.
What are the symptoms of pyrrolizidine alkaloid poisoning?
- jaundiced skin (from impaired liver function)
- rough unkempt appearance
- prolapsed rectum
- oedema of tissues of the digestive tract
- abnormal behaviour. Horses may have neurological signs such as “head pressing”
- cattle may have a bloated appearance
If you want my honest opinion, rather avoid Comfrey and any products containing it, altogether.
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