I, too, have recently used Grapefruit Seed Extract (one drop per ounce of water), applying it several times a day for a couple of days, and it immediately dried up and mostly disappeared. I'm in the process now of applying once a day for a more extended period of time.
Grapefruit seed extract "citricidal" cures ringworm. I used about 4 drops in 3 tablespoons luke warm water, twice daily, applied with cotton-wool pad. It got rid of my cat's ringworm in about 7 days.