Comfrey is a genus of flowering plants in the borage family, Boraginaceae. Symphytum is native to northern temperate regions of Asia and North America, with a wide introduced distribution on both continents. There are 59 recognized species. You have purchased the leaf of Symphytum officinale, aka true comfrey or common comfrey.
Comfrey has been widely used for centuries for an assortment of internal ailments, but it's now considered unsafe for internal use, due to the pyrrolizidine alkaloids that it contains. The FDA and EU have banned oral comfrey products. In actuality the danger is primarily from the roots, which contain up to ten times as much alkaloid as the leaves. At present I only use the leaves and stems.
I offer several salves, and also dried comfrey leaves which I recommend for musculoskeletal complaints.
Comfrey has been used for bruises, strains and sprains, tendinitis syndrome, knee joint injuries, non-active gonarthrosis, insect bites, mastitis, fractures, osteoporosis, and skin inflammation. My family finds that a comfrey poultice or salve warmed or combined with castor oil is a soothing remedy for musculoskeletal complaints. Comfrey contains allantoin, which promotes new skin cell growth. It contains rosmarinic acid and tannins, which can help reduce inflammation and relieve pain. Studies have found it to exhibit inhibition against S. aureus, B subtilis, P. aeruginosa and S. typhi. This speaks to its use as a wound healer and protectant. Comfrey contains a wide variety of critically important bioactive constituents, amino acids, flavonoids, triterpenes, terpenoids, saponins, sterols, mucopolysaccharides and other hydroxycinnamic acid derivatives.
Dry comfrey leaves are covered in tiny hairs, which can irritate the skin and cause dermatitis. Making a warm, moist poultice or using them in an oil usually avoids this. Use just a small amount on a test area before slathering it on.