Externally, Comfrey is a wonder when it comes to skin care — it eases swelling (bruises, sprains, or pulled muscles) and inflammation (diaper rash, varicose veins and arthritis), and also promotes cell regeneration and healing. Comfrey is useful in healing stubborn skin ulcers, bedsores, and other lesions. It can also promote the healing of minor burns, eczema, and psoriasis, treat athlete’s foot, soothe bee stings, and other insect bites.
Comfrey : Medicinal Uses & Benefits

Comfrey is a marvelous herb and is one of the best-known healing herbs of all times. Well known and widely used by early Greeks and Romans, its very name, symphytum, from the Greek symphyo means to "make grow together", referring to its traditional use of healing fractures. Comfrey relieves pain and inflammation caused by injuries and degeneration, especially the symptoms of rheumatoid arthritis and osteoarthritis. Comfrey creams and oils can be used in arthritic pain relieving massages.

Comfrey salves, ointments and teas are best know for the topical treatment of burns, skin ulcerations, abrasions, lacerations, flea and insect bites, and just about any skin irritation. Comfrey's astringent tannins form a protective surface over wounds that promotes healing. You may want to try comfrey or allantoin skin creams for diabetic sores.

Fresh leaves can be applied to bruises, fractures, sprains, and other injuries. Many healing effects of comfrey are attributable to allantoin, a compound shown to speed cell production both inside and outside the body. Comfrey works so fast that many herbalists will add antibacterial herbs such as goldenseal or thyme to comfrey salves to prevent sealing bacteria inside a fast healing wound.

Comfrey also has a healing effect on ulcers, and a general soothing effect on the mucous membranes, making it invaluable in soothing sore throats and coughs.

In the late 1970s experimental data showed lab rats fed comfrey 3 to 4 times their body weight over a long period of time developed liver damage. It would take a human drinking 3 to 4 cups of comfrey tea for 140 years to achieve the same effect, still it must always be considered that what is safe for the majority can cause allergic reactions in a few. Herbalists are divided on the use of this age old herb, which has been used safely for centuries. (use your own judgment and common sense). Most herbalists limit its use internally to short term applications some say it should only be applied externally, others point to the fact that a cup of comfrey contains less cancer causing potential than a can of beer

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Comfrey Side Effects: Internal use has become controversial due to the high content of PAs, however the be herb has been used by both humans and animals safely for centuries. (use your own judgment and common sense). Symphytum asperum, Prickly comfrey contains more of the pyrrolizidine alkaloids (PAs) than the common Symphytum officinale used in our balm. The most damaging studies are of the isolated extract symphytine, holistic use of the whole herb results in preparations containing much lower, if any amounts of PAs.
As with any product used internally or externally, consult you physician before use.