Comfrey

Comfrey will make you heal up faster but using it on an open wound is controversial because it's bad for your liver. I figure that means it's for short-term use, not long-term use.

Here's an article on Comfrey that I haven't read all the way yet. This article on maximum dosage: Literature on comfrey often concentrates on PAs, recommending a restriction of the duration of treatment, also with externally applied comfrey preparations. However, in Germany, the restriction limiting application to 4–6 weeks/yr applies only to preparations containing more than 10 µg, but less than 100 µg pyrrolizidine alkaloids (daily allowance; Bundesgesundheitsamt, 1992). Fully licenced medicinal products available today contain depleted or PA-free extracts. The application results in far below the daily allowance of 10 µg. As a consequence there are no restrictions in Germany on these products as regards the duration of treatment (Bundesgesundheitsamt, 1992).