One of my dd's had ringworm last year for an extended period of time. I gave her (by mouth and on topically) colloidal silver spray, and then made a solution to be sprayed onto the ringworm. My solution had 1/4 cup of water, 3 or 4 drops of lavender essential oil and 3 or 4 drops of teatree oil. I shook it up and sprayed it (used an old spray bottle, cleaned it well). I let her take her bath first (very warm bath) and then patted dry her arm, applied the solution. I did this twice a day. It was getting better, but very slowly. I called my sister who is a nurse, and who uses holistic health products, and she said that I should keep on doing the same, but also look at her diet and try to heal from within. She said take away any sugary things, give absolutely no white flours and see if that helped. The combination of all of the things made a big difference.
It did however take a few months for it to go away completely.
I hope it works for you. Teatree oil is an antifungal, colloidial silver is antifungal, and lavender is just very soothing healing to the skin.