Severe hair loss may be caused by androgenic alopecia, spot baldness, seborrheic dermatitis and other diseases. 1. Androgenetic Baldness: Androgenetic Baldness may be related to heredity, androgens, excessive stress, prolonged late night, poor dietary habits and other factors. Patients may show that their hair becomes thinning and gradually fall off, accompanied by excessive secretion of scalp oil, greasy hair, itching and other symptoms, and severe hair loss. 2. Patchy baldness: the etiology of patchy baldness has not been perfected, and it may be caused by autoimmune disorders, heredity, mental stress and other factors. Patients may have sudden patchy alopecia, which is characterized by severe hair loss. 3. Seborrheic dermatitis: the etiology of seborrheic dermatitis has not been clarified, which may be caused by heredity, pathogen infection, improper diet, immune disorders and other factors. Patients can appear more gray-white dandruff on the scalp, accompanied by mild itching, erythema and other symptoms, when too much oil accumulates in the scalp, can lead to serious hair loss. There are many reasons for severe hair loss, and it is recommended that patients seek medical examination to identify the cause of the disease and take relevant treatment measures under the guidance of the doctor.