After a baby has a fever, blood is drawn to check the following aspects: i. White blood cell count. A significantly increased white blood cell count indicates that the child has a bacterial infection and needs to be treated with antibacterial agents. Second, the neutrophil count. An increased neutrophil count is a bacterial infection, and if it is lower than normal, it indicates a viral infection. If the neutrophil percentage decreases and the lymphocyte percentage increases, it indicates that the child has a possible viral infection. If the neutrophil percentage number is higher, it indicates that the child has a bacterial infection and that there is a possibility of further aggravation in the development of the disease. Third, the number of lymphocytes, the number of lymphocytes increased, if the absolute value of lymphocytes and lymphocyte percentage, these 2 values are higher than normal value is a viral infection. Excessive eosinophils, absolute eosinophils and absolute eosinophils, is one of the indicators to determine whether the child has allergies and possibly allergic diseases.