Comfrey has been associated with bone healing for centuries, enough to be known by the nickname “knitbone”. But its reputation as a bone-healing herb probably has more to do with the poor state of medicine in medieval times, rather than its true properties.
At least as far back as ancient Greece, comfrey has been used externally on injuries involving swelling, bruising, and soft tissue trauma. So far so good. These are study-backed medicinal uses for comfrey.
But by the time the middle ages rolled around, comfrey had evolved into a cure-all. Medieval doctors wrote that comfrey could be used for just about anything:
“Spitting, pissing Blood, Inward Wounds & Bruises, Phtisick, Bloody Flux, Terms stops, Whites, Nervs cut, Muscles cut, sharp Humors, Wounds, Ruptures, broken Bones, Knotted Breasts, Hemorrhoids, Inflamation, Gout, Pained Joynts, and Gangreans.” — The Pharmaceutical Journal
Over time, this traditional use evolved into the widespread belief that comfrey could help “knit” broken bones back together.
It Doesn’t Knit Bones—What Does It Do?
Sadly, comfrey’s medicinal uses don’t extend to bone healing. But that doesn’t make it useless!
Comfrey contains allantoin, a compound known to stimulate cell proliferation and support tissue regeneration. When applied topically, allantoin encourages rapid growth of surface tissue, particularly skin cells.
The other main active compound in comfrey rosmarinic acid, an anti-inflammatory that is in many other herbs, such as rosemary and sage. Topical comfrey ointments—both traditional and commercial ones such as Kytta-Salbe—have long been used to soothe stiff joints and reduce pain and swelling. One study even suggested that comfrey “may be superior to Diclofenac gel.”
How Comfrey Is Used in Modern Times
Today, comfrey is still commonly used in homemade salves to promote overall skin recovery. It’s also used in ointments and poultices much the same way it was used in ancient Greece: for injuries involving swelling, bruising, and soft tissue trauma.
Even in these cases, comfrey is viewed as a supportive herb rather than a primary treatment. It is not a substitute for medical evaluation, diagnosis, or care. And it’s definitely not a cure-all.
Should Comfrey Be Used on Open Wounds At All?
Short answer—no.
The same allantoin that makes comfrey useful for skin regeneration can also issues when it comes to open wounds. In some cases, comfrey can lead the outer layers of tissue to heal faster than deeper structures. In the case of fractures, deep bruises, or puncture wounds, this can trap inflammation or infection beneath the skin.
Because of this risk, comfrey should never be applied to open wounds, deep punctures, or untreated fractures. Using it too early or inappropriately can do more harm than good and may delay proper medical treatment.
Want to Grow Your Own Comfrey?
You can easily propagate your own from root cuttings or crowns, and use your homegrown comfrey to make medicinal salves, ointments, and poultices. Get plants for your garden at the link below!
Disclaimer: Comfrey is not recommended to take internally, because it contains pyrrolizidine alkaloids (PAs), which are linked to liver toxicity and possibly cancer. We are not medical professionals, and are not offering medical advice. Please consult your doctor or a medical professional if you have any medical concerns.