It can cause malnutrition and therefore cause
hair loss, and also autoimmune disorders, including those that cause
hair loss. The dandruff and scabs suggest Celiac.
You can try Nizoral shampoo, Dove shampoos, Loreal Vive shampoo, and/or Neutrogena shampoos. All have been helpful for me. If your scalp is extremely oily, you can control that just by doing a vinegar-water rinse at the end.