The causes of sudden hair loss may be related to androgen level disorders, baldness, medications and so on. 1. Androgen level disorder: excessive androgen causes hair loss, also known as seborrheic alopecia, when there is too much androgen, hair follicles shrink and degenerate, thus leading to hair loss. 2. Patchy baldness: it is an immune-related disease, often late at night, emotional depression will aggravate or induce the disease, manifested as round or irregular patchy hair loss, without other accompanying uncomfortable symptoms. 3. Drugs: chemotherapy, high blood pressure control drugs and the use of contraceptives can cause temporary massive hair loss. Sudden hair loss should go to the hospital in a timely manner, to clarify the cause of hair loss, follow the doctor’s instructions for standardized treatment.