Hair is particularly itchy when it is not washed for two days may be caused by seborrheic dermatitis, ringworm of the head and so on. 1. Seborrheic dermatitis: it is a common chronic inflammatory skin disease, the cause of which is related to heredity, disease, infection, immunity and spirituality. Happens in the body sebum secretion of the part, if the hair in the head, can be manifested in the head itchy red spots, follicular papules, covered with greasy scales or scabs, which can lead to the hair two days without washing is particularly itchy. 2. Tinea capitis: an infectious disease caused by fungal infection of the scalp and hair. The main manifestation of head lesions, can be accompanied by itching, baldness and other symptoms, which leads to hair two days without washing is particularly itchy. There are many other causes of itchy hair in two days without washing, which should be taken seriously, timely consultation, identify the cause of the disease, and follow the doctor’s instructions for further treatment or therapy.