Well ringworm is just a topical thing. You scrub it all off really well and wash everything really good, let the immune system take over. A little bleach in the water you use to clean with helps, like even to clean the animal. I had some evil foster cats that we could not bathe, they ended up bringing ringworm to my house. I had a hard time getting rid of it in the cats because bathing them was impossible. Finally another rescue person told me just to wash everything in the house in hot water and bleach and then use 10-1 water/bleach and dab it on the cats ringworm areas instead of bathing with the special dips, etc., from the vet where I worked.
It cleared it right up. But the vets I've worked for talk about how ringworm is because of weak immune system. I think it was boosting their diets and giving them the L-lysine and quality food, cleanliness, is what got rid of it.
I guess bleach isn't exactly NATURAL but it is plain and unfancy and cheap. But I imagine other things that would kill germs would do the same trick. The main thing is just getting everything really clean.