T.M.
I have always used Blue Star Ointment. You can find it over the counter, in any drugstore. Sometimes it maybe hard to find. It has been on the market for awhile. I remember my mom using it when I was small. Blue Star Ointment has always seem to work for my kids. If you put it on the ringworm as soon as you see it, it quickly kills it within a few days. I have also heard of the antifungual cream or spray that you use for athletic feet works as well. I have not tried that yet.
Good Luck