6 months old baby neutrophil percent low, commonly due to the following reasons: a. It may be a normal physiological phenomenon, not disease causes. 6 months old baby has low neutrophils, the child will not have any clinical abnormal symptoms, not considered to be the cause of disease. Second, children suffering from viral infectious diseases, such as viral infections caused by upper respiratory tract infections, such as hand, foot and mouth disease and other states when lymphocytes and monocytes will also be elevated, while the performance of neutrophils is low. Third, poor immunity in children, when the application of cephalosporins, penicillin antibiotic treatment, will make the white blood cell count will drop at the same time, the percentage of neutrophils will be low. Four, such as suffering from blood system diseases, iron deficiency anemia, aplastic anemia, megaloblastic anemia and other conditions will have low neutrophils, accompanied by a decrease in the number of platelets and red blood cells.