Causes of dandruff. In a person with dandruff, usual skin renewal cycle gets speeded up causing more patches of dead skin cells on the scalp. Dandruff isn’t a sign of dirty hair, although it can be triggered by too much washing as well as too little. Dandruff can also be linked to: 1  Seborrhoeic dermatitis causing oily and flaking skin. 2  The skin fungus malassezia. 3  Psoriasis.