We went on a gluten free diet (foods that contain wheat, barley, rye and possibly oats) for other reasons
, and realized we all got scalp relief - no more itching, crusting, etc. Food intolerances, like gluten and cow's milk foods, when not digested, allow yeast to overgrow. It causes yeast overgrowth in and on the body. Of course, sugar is another promoter of yeast. But the gluten free diet relieved all of our scalps about 95%.
Only minimal symptoms left behind.