Less hair on both sides of the forehead is a sign of seborrheic alopecia. This is because seborrheic alopecia can be manifested as an upward movement of the hairline, especially the hair on both sides of the forehead, or the hair on the top of the head may be thinning and becoming thin and soft. In the case of seborrheic alopecia, the hair may be thin and soft, and gradually fall out. It is mainly caused by genetic factors, especially the excessive secretion of androgens, which leads to excessive secretion of sebum by the sebaceous glands and affects the nutrition of the hair, resulting in thinning and softening of the hair, which may lead to the occurrence of hair loss. For seborrheic alopecia, active treatment is needed to control the rate of hair loss.