I am going to chime in on this one knowing that I will almost certainly regret it after I get done. First of all ringworm is caused by a fungus. Itf you know that it is a fungus yes you can kill a fungus topically but as with humans if you are having some type of fungal issues whether it be athletes foot or a yeast infection your doctor/vet will prescribe an internal treatment which will be the most effective method of getting the cause, (fungus), killed. In the case of bovine ringworm the absolute best and easiest way to kill, (cure), ringworm is to use Fulvison orally 2 times. I have used it several times through the years and never had it ever fail to work. You will have to get it via prescription from your vet. Linking this to the thread about where have all of the readers/posters gone, I have stated this method several times over the years and people seem to want to argue over this and if a person ever asks for help with a feeding issues, bar the door because by the time that conversation gets overwith a beginner would surely have to be more confused after all of the advice than B4 they started looking for help. I love this site and have read it pretty much daily since the beginning. Good luck! If you want an EASY, FAIL SAFE method to clear up ringworm, try Fulvison once and then get back to us with your results. I dare you to. You'll like it.