I developed a herbal garden for a living history village and included Comfrey. A volunteer was bitten by a Brown Spider while digging into old boxes of linens with a resulting nasty open sore on her forearm. The doctor stated the only treatment was to keep it clean and prevent infection. The hole would get bigger and not heal for at least a month. I suggested she try a comfrey poltuce and gave her some of the leaves from the garden. To everyones surprise, and the doctor, the wound healed in one week. I do not suggest anyone take comfrey internally but I am now a believer in it's healing powers externally.