Comfrey is an herb with a long tradition of use, historically valued for its supportive role in external applications. This plant is traditionally used in preparations intended to support the natural recovery of muscles and joints following physical exertion or minor injuries. Comfrey is appreciated for its soothing properties that help ease occasional swelling and minor discomfort in muscles. It is also used to assist with the care of bruises and strains commonly associated with sports activities.
Source(s):
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3491633/