The person in question had it on their two big toes. The fungus was highly yellow near the top of the nails, then a frightening black near the bottom. Candida has been an issue, but is clearing up nicely thanks to MMS, finally--after strenuous yeast free diet and wild oregano, and more failed to do the entire job.
Anyway, we separated the nail from the toe bed somewhat so we could get the neem oil in there. It sounds disgusting but separating the nail really did the trick, I think. The Neem oil settles in there and will stay for days if you don't wash it out. Within a week the fungus and black was nearly completely gone. It was only applied 3-4 times. There is still a dark spot on one nail which is more red than black now, but I feel a couple of additional applications of the neem oil should finish it off nicely. Two thumbs up!