Comfrey (Symphytum officinale) has a long history of traditional use for treating injuries such as bruises, sprains, and fractures. The plant contains several biologically active compounds, including allantoin, rosmarinic acid, and tannins, which are believed to promote cell proliferation and reduce inflammation. Modern scientific studies, particularly from Europe, have provided moderate evidence supporting the topical use of comfrey for musculoskeletal injuries. Randomized controlled trials have demonstrated that comfrey cream or ointment can significantly reduce pain and accelerate healing in conditions like ankle sprains, muscle pain, and back pain, compared to placebo or standard treatments.

However, safety concerns limit comfrey's use. Oral comfrey or products containing certain pyrrolizidine alkaloids (PAs) are considered unsafe due to the risk of liver toxicity and should be avoided. Most clinical research focuses on topical preparations that are PA-free or have very low levels of these compounds. Overall, the evidence supporting topical comfrey for injury-related pain and swelling is moderate (rating 3), with multiple clinical studies confirming benefit, but additional high-quality research is warranted. Comfrey should only be used externally and on unbroken skin, and not for prolonged periods.