to figure this out first look at what type of hair products you are using. certain shampoos can be harsh or drying to the scalp. try switching to a shampoo that is marketed for dry hair or one that claims to add moisture to your hair. if this doesn't help you may need to see your local dermatologist to have your scalp examined for psoriasis seborrhea or another form of scalp dermatitis. a biopsy may be necessary to fully understand what's going on.
what could be causing my scalp to suddenly become dry and flaky?