Canada's health agency says such products may contain a compound called echimidine that may cause liver damage.
The comfrey herb is found in herbal and homeopathic preparations, and is marketed to treat digestive problems, lung problems, arthritis, ulcers, bruises, wounds, and sprains/fractures. Comfrey is also found in lip balms, burn salves, diaper rash ointments and other therapeutic skin care products.
Two species of comfrey - prickly comfrey and Russian comfrey -are already prohibited from being used in therapeutic products in Canada because they contain echimidine. There have been previous reports associating the ingestion of comfrey (teas, capsules and leaves) with liver damage although no cases of liver toxicity related to comfrey have been reported in Canada.
The agency is currently conducting a market review to determine if any health products on the Canadian market contain comfrey, echimidine or the two prohibited comfrey species (prickly and Russian). It has issued letters to manufacturers of approved health products that contain comfrey - those with Drug Identification Numbers (DINs) on the label - requesting that they submit evidence that demonstrates their products do not contain echimidine or the two prohibited comfrey species.
Manufacturers, importers and distributors of unapproved products - those without DINs on the label - are required to remove these products from the Canadian market immediately.
The agency said it will take further action when it has completed its review.