Tinnea infections are a PITA.
1. Constant and consistent application of the antifungal.
2. Application well beyond the appearance of resolution, as infection becomes subclinical, yet very much lurking in the tissue.
3. Eradication of sources of reinfection can be problematic as the source; could be unidentifiable thus reinfection and repeat of steps one and two, multiple sources for reinfections of which some are identified and eradicated, but the source not identified creates the reinfection and back to square one.
4. Vicious circle of infection, treatment, and reinfections. Frustrating.
In this particular case the discussion has been about ring worm, which can occur in humans also. But another nasty tinnea infection is athletes feet. That is another PITA.
Professional advice. Stick with the commercial products which have passed the FDA safety and efficacy criteria. Studies were conducted to prove these two points and the volume of knowledge of the product and known risks are published.
Hang in there Tort.