OK, I know it comes from pixies like Tink, but why?
Does Tink have really bad dandruff? They probably don't have Head 'n' Shoulders at Neverland.
Or is it more serious, like psoriasis? Or some other "jungle rot" infection?
Or are pixies even less "humanoid" than they appear? Is that thing that looks like a dress actually fur, and pixie dust is actually some sort of "animal dander" like my labrador sheds?
Or is Tink and her kind more reptillian, constantly shedding their skin so that it comes off in dust-like flakes?