Comfrey Central - A Clearinghouse for Symphytum Information

Topical Application of Comfrey

It is generally accepted that the topical application of comfrey could not result in poisoning because:

  1. absorption of PAs are limited,
  2. the majority of PAs in plant material is in the N-oxide form,
  3. conversion of N-oxides to their parent base is minimal when the PAs are absorbed through the skin,
  4. N-oxides are quickly excreted showing no to low toxicity,
  5. the PAs in comfrey are of the low hepatic toxicity type.

Indeed, there have been no reports of poisoning from topically applied comfrey.

The extent that PAs are absorbed by the skin was explored in one limited study (two rats per group) using comfrey PAs and measuring urine excretion. Absorption by the skin results in about 20 times less metabolites in the urine than when administered orally. In addition, dermally administered PA N-Oxides of Symphytum were not converted to the parent base, while oral administration resulted in detectable amounts of the parent base in the urine[50].

2004 Dorena Rode       Acknowledgment