One year old baby hair yellow, common causes include genetic, disease factors. 1. Heredity: baby hair color, density, etc. by the parents of genetic factors, if the parents have yellow hair and other conditions, the baby also has a certain chance of inheritance, without special intervention. 2. Disease factors: nutrient deficiency, megaloblastic anemia, phenylketonuria, etc. may lead to baby hair yellow, accompanied by growth retardation, mental retardation and other manifestations. More than a year old baby hair yellow, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.