There are many reasons for itching without washing your hair for a day, including physiological and pathological reasons. Physiological reasons are generally seen in oily hair, the head sebaceous glands secrete oil and fatty substances will lead to greasy hair, itchy scalp, consider using oil control shampoo. In addition to physiological reasons, it may also be due to the following pathological reasons: 1, seborrheic dermatitis: seborrheic dermatitis occurs in locations where sebaceous glands are more distributed, such as the scalp, face, etc. Patients with hypersecretion of sebaceous glands will have excessive oil secretion in the head, there will be greasy scales or scabs, accompanied by varying degrees of itching. Daily washing of the hair cannot cure seborrheic dermatitis, but it can relieve the itching symptoms to some extent. If the itching is severe, it is recommended to take oral or topical medication under the guidance of a doctor; 2. Head lice: there are lice on the scalp, the head itching symptoms will occur after being bitten by lice, and the scalp itching will be severe if you do not wash your hair for a day. After the discovery of lice or eggs to cut short hair, daily hair cleaning with sulfur soap, but also with topical medication. At the same time, it is necessary to disinfect household items such as hats, combs and pillows.