In every horse owners life there is the day when you have to deal with wounds. Horses are really prone to proud flesh. I experienced that myself many times over and have used different ways to control the developing of proud flesh including using copper sulphate.
However the one I loved best, was easiest to use and was not a health hazard to your horse (if they would lick and scratch on wounds which have copper sulphate on them) is the turmeric paste.