Four months baby frequent fever can be seen in the respiratory tract infection, infectious diarrhea disease, urinary tract infection or hemophagocytic lymphohistiocytosis, etc., need to be analyzed on a case-by-case basis. 1. Respiratory tract infections: such as acute upper respiratory tract infections, may appear repeatedly fever, may be accompanied by nasal congestion and runny nose and other symptoms, perfect infection indicators can be seen in the viral infections caused by normal infection indicators can be seen in the bacterial infections caused by elevated. 2. Infectious diarrhea disease: such as acute diarrhea disease caused by Escherichia coli, the above symptoms can occur, accompanied by a significant increase in the number of stools or a significant change in the nature of the stools, and improve the routine stool examination can be seen in the increase of leukocytes. 3. Urinary tract infection: such babies often manifested as recurrent fever, urinary tract irritation signs, such as urinary frequency, urinary pain and other symptoms are not obvious, perfect urine routine can be seen in elevated leukocytes. 4. Hemophagocytic lymphohistiocytosis: it is a syndrome of multiple organ function damage, irregular fever can occur, poor response to antipyretic drugs, can be accompanied by anemia and bleeding, liver and spleen lymph node enlargement and so on. 5. Other: such as tuberculosis, there may be repeated high fever, continued for 2~3 weeks and then turned to low fever, accompanied by symptoms of tuberculosis poisoning, dry cough and respiratory difficulties. Four-month-old babies with frequent fevers are recommended to actively consult a specialist physician to determine the cause of recurrent fever.