Gray hair in children may be caused by heredity, lack of trace elements, endocrine disorders or lead poisoning. You can check the blood routine and trace elements. 1. Routine blood test: including red blood cells, platelets, white blood cells, platelet pressure, hematocrit and other items, to see if the anemia is caused by malnutrition, or tyrosine test, to clarify whether it is due to the low amount of tyrosinase in the serum or the lack of tyrosinase, which leads to the growth of gray hair in children. 2. Trace elements: The examination includes iron, zinc, copper, lead, iodine, selenium and other elements. Through this test, it can be clear whether it is due to the lack of the trace element zinc that causes children to have gray hair, as well as to rule out whether it is due to lead poisoning that causes children to have gray hair. If children have gray hair, they should go to a specialist hospital in time to rule out pathological factors.