The darkening of a child’s skin may be caused by environmental factors, heredity, and disease. Children who do not pay attention to sun protection, often in and out of the external environment, exposure to ultraviolet rays, may lead to skin darkening; parents or grandparents of the family with dark skin, affected by genetic factors, the child’s skin may also be darker. In addition, pathologic factors, such as congenital adrenal disease, may lead to increasingly dark skin, and some children have symptoms caused by electrolyte disorders. There may be other reasons for children to become darker, it is recommended to go to the hospital in time, complete the examination to clarify the cause of the disease, and then give targeted treatment or therapy under the guidance of the doctor.