Hello,
It can be due to dandruff which can be due to internal or external causes.
Dandruff can cause either an overly dry scalp with itchy white flakes that may be waxy or greasy, or it can manifest as an oily scalp with scales.
Internal causes include hormonal imbalance, poor health, poor hygiene, allergic hypersensitivity, lack of rest, emotional stress, excessive consumption of sugar, fat or starch and heredity predisposition.