Dandruff after washing your hair may be caused by seborrheic dermatitis, dry skin, scalp-type psoriasis, etc. It can be improved by general treatment, medication and physical therapy. 1. Seborrheic dermatitis: a chronic inflammatory skin disease that mainly occurs in the seborrheic overflow part of the skin, and dandruff can occur after washing the head. It is recommended to use drugs such as ketoconazole ointment, tacrolimus ointment and other medications under the guidance of a doctor. 2. Dry skin: If the weather is dry, and the use of strong cleansing shampoo, may lead to dry skin on the head, resulting in dandruff after shampooing. It is recommended to replace the shampoo immediately, can use nourishing, moisturizing shampoo. At the same time, do not change shampoo frequently, so as not to have an impact on the hair quality. 3. Scalp-type psoriasis: dandruff after shampooing, may be caused by scalp-type psoriasis, need to go to the hospital in a timely manner, under the guidance of the doctor, external use of vitamin D3 derivatives such as carboxytriol, calcium-regulated phosphatase inhibitors such as pimecrolimus ointment, but also the use of ultraviolet light irradiation and other methods of treatment, so as to alleviate the symptoms. Dandruff after washing your hair, you need to go to the hospital in time to find out the cause, symptomatic treatment, the above drugs should be used in accordance with medical advice.