A short period of time without washing hair generally does not cause harm, while a long period of time without washing hair can appear odor, affecting the appearance, and even lead to head lice disease, seborrheic dermatitis and other diseases, it is recommended to pay attention to personal hygiene in general, and wash your hair regularly in order to keep your hair clean. Hair is a fiber produced by the hair follicle, the main component is keratin. The scalp produces sebum, and too much sebum will adsorb dust, causing the reproduction and growth of microorganisms, as well as being prone to odor or an untidy appearance. Prolonged failure to wash hair and pay attention to hygiene can also lead to head lice infestation. Head lice bite the scalp can appear red spots, pimples, accompanied by intense itching, seriously affecting sleep and daily life, scratching the skin lesions can be broken, may cause secondary infection. Head lice are contagious and can be transmitted to others if not treated in time. Prolonged failure to wash hair can cause excessive sebum secretion, breeding Malassezia bacteria, leading to the occurrence of seborrheic dermatitis. Seborrheic dermatitis can be manifested as chaff-like flaking, and in severe cases, scabs, vesicles, and odor can also appear. Seborrheic dermatitis can present with severe skin infections and can also be recurrent, affecting the patient’s normal life and mental state. It is recommended to develop good daily hygiene habits, wash your hair diligently, keep your hair clean and dry, and prevent the occurrence of the disease.