The causes of dry and itchy scalp consider damaged scalp barrier and bacterial growth, as follows: First, damaged scalp barrier: this situation of damaged scalp barrier is often itchy in the morning after shampooing, or in the evening, or in the first night after shampooing, the next morning the skin is itchy. The itchy scalp appears in a very short period of time, mainly due to excessive time, high water temperature, repeated scratching in the process of washing hair, as well as unclean rinsing, and more importantly, shampoo is too stimulating as well as too strong alkaline. In the treatment, you need to change the way you wash your hair, change the shampoo, and choose a soft alkaline shampoo. Second, the breeding of bacteria: the first day after washing the hair, the second day itchy, the third day or itchy, this situation is due to the breeding of bacteria, the scalp has a very large number of spores of furfur, also called Malassezia, which is a kind of fungus, this fungus is very easy to breed on the scalp, especially in the case of not washing the hair. In the treatment, first of all, you need to keep your hair clean and hygienic. If you have a very oily scalp, i.e. oily skin, you can wash your hair once a day, if not, you can wash your hair once every 3-5 days. If there is dry and itchy skin after shampooing, then you need to go to the dermatology department to find a professional doctor for medication, such as oral compound glycyrrhetinic acid tablets and olopatadine hydrochloride tablets, in the external medicine can apply selenium disulfide shampoo to shampoo the hair, and then topical application of Econobetone cream, while avoiding spicy and irritating food, reduce the intake of fried and sweet food.