Through trial and error, I have come to find that I may have a Vitamin B12 deficiency. I have been taking one B12 tablet a day for a couple of months now and it seems to be helping. It takes some time to see results, possibly 4-6 weeks to notice the "sand" going away. My scalp seems to be slowly healing, after years of trying to figure out what is going on, I think that a B12 deficiency may be why. I am not a doctor, but thought I would share this in hopes it helps someone with this frustrating issue.