The symptoms of itchy scalp may be caused by scalp allergy, seborrheic dermatitis, fungal infection and other factors. 1. Scalp allergy: If patients use bad shampoo or after hair coloring, the chemical substances in the shampoo or hair dye stimulate the scalp, thus causing local allergic inflammation, and the patient develops itchy scalp symptoms, accompanied by local pimples or small blisters. 2. Seborrheic dermatitis: usually in the normal human skin surface will exist Malassezia, if the patient usually do not pay attention to local hygiene, will lead to Malassezia is activated, thus producing a large number of sebum, when these irritating substances stimulate the scalp, will cause scalp inflammation, resulting in itchy scalp. 3. Fungal infection: if the patient is infected by red trichophyton and purple trichophyton when the body resistance drops, it will make these fungi stimulate the hair follicles and produce local inflammatory reaction, leading to the symptoms of itchy scalp. When the patient has an itchy scalp, it is recommended to go to the hospital in time for treatment, so as not to delay the condition leading to the aggravation of the disease.