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Formerly much valued as a herbal remedy but not now recommended for ingestion though application to the skin is, probably, harmless.
From the Greek, ‘sympho’, ‘to unite’ resulting from the plant’s alleged ability to knit bones together.
From the Caucasus Mountains.
Symphytum spp., comfrey
Contains pyrrolidizine alkaloids including heliosupine and cynoglosine. The young leaves contain a highish concentration which is reduced as the leaves enlarge and age.
Trials have suggested that ingestion of 6kgs of comfrey would be necessary to cause severe liver damage. Even so, ingestion as a herbal remedy is not recommended. The same tests found that absorption through the skin is twenty to fifty times less efficient than ingestion so comfrey creams offered as herbal remedies are unlikely to cause any problems.
The only known incidents relating to comfrey result from excessive use of herbal capsules or tea.
John Gerard said of the benefits of the plant ‘The slimie
substance of the roote made in a posset of ale, and given to drinke
against the paine in the backe, gotten by any violent motion, as
wrestling, or over much use of women, doth in fower or five daies
perfectly cure the same, although the involuntarie flowing of the
seed in men be gotten thereby.’
‘Symphytum’ comes from a Greek word meaning ‘to knit together’. It does contain allantoin, a substance which is said to increase cell generation but the presence of pyrrolizidine alkaloids makes it dangerous to ingest. Some sources suggest that even in ‘beneficial’ amounts, ingestion of comfrey for more than five days could cause permanent liver damage in children.
The work on the effects of the pyrrolizidine alkaloids in Symphytum species is of interest in the context of Jacobaea vulgaris (syn. Senecio jacobaea), common ragwort, for two reasons. The concentration of PAs in both genera is broadly similar so the results for comfrey can be read across to ragwort. This is particularly important given the persistence of the lies about skin absorption of ragwort. But, there is also the point that this work was done on comfrey, where its use in herbal preparations creates an identifiable concern, and not on ragwort where the concerns are, largely, hysterical.