Dandruff may be caused by physiological factors, contact dermatitis, seborrheic dermatitis and other factors. 1. Physiological factors: often stay up late, more oil secretion, and do not often wash your hair, will make the scalp always dandruff, usually no other clinical symptoms, should wash your hair diligently, and avoid staying up late, may be improved by itself. 2. Contact dermatitis: the frequent use of some stimulating toiletries may induce contact dermatitis, which will lead to dandruff on the scalp, may also be accompanied by itching, redness and other symptoms. 3. Seborrheic dermatitis: it may be related to genetic factors and environmental factors, which can make the scalp area frequently appear greasy scales, accompanied by itching, and even hair loss and other symptoms. Dandruff on the scalp, lasting for a long time, it is recommended to go to the dermatology department of the hospital for examination and treatment to avoid aggravation of the lesions.