Comfrey leaves have similar properties to the roots. The roots tend to be more potent and the leaves are usually more palatable. They can both be used in slaves, ointments or poultices. I have found when using comfrey in a poultice, after several days, the area in contact with the poultice can become itchy due to the tiny hairs that are found on the surface of the leaves and stem. The leaves are commonly used as tea to sooth tissue inflammation. Comfrey can also be administered via capsules.
Believe it or not, comfrey is banned from therapeutic use in Australia, Canada and Germany. It was once commonly used internally to treat gastrointestinal problems. However, in 1954, scientists determined that comfrey contains pyrrolizidine alkaloids. These alkaloids are considered to be potentially hepatoxic, carcinogenic, and mutagenic. Supposedly, according to several isolated studies on pyrrolizidine alkaloids, over a period of time with repeated use, these alkaloids can build up in the liver, overwhelming it and causing liver toxicity. However, there have been few concrete cases of this occurring in humans. Paul Bergner wrote an online article entitled, “Symphytum: Comfrey, Coltsfoot, and Pyrrolizidine Alkaloids.” In his article, he theorized that there are probably many more cases of PA poisoning. Unfortunately, people may not associate their problems to comfrey because the symptoms can take several weeks to manifest.
It has been determined that the concentration of pyrrolizidine alkaloids in comfrey varies. The stage of growth the plant is in when harvested can also determine how many alkaloids are present. The greatest concentrations can be found in the roots and young leaves. Mature leaves were shown to have the lowest concentration of pyrrolizidine alkaloids.
Should we abandon the potential healing benefits of comfrey because of a single potentially harmful component? Pyrrolizidine alkaloids are toxic on there own. However, what needs to be determined is whether this plant is toxic when used in its entirety. Perhaps synergy plays a role in comfrey’s ability to heal regardless of potentially toxic components? I believe that the sum of comfreys benefits out weigh the potential risk from one component. Perhaps all of the benefits from the vitamins and minerals in comfrey counteract any disabling affects the pyrrolizidine alkaloids may cause. However, individuals with preexisting liver problems may become more susceptible to liver toxicity.
It seems extreme to ban a plant that has proven through the years to be beneficial to the human body. Although comfrey contains one toxic alkaloid, it is likely that the combination and strength of the entire plant contributes to its effectiveness and less to its potential danger. Of course, as with all herbal medicines excessiveness should be avoided and when in doubt consult with your health care practitioner.