Three and a half year old baby fever each time interval 4 hours can not take antipyretic medicine, need to depend on which kind of antipyretic medicine, such as acetaminophen drops can be used every 4 hours, but ibuprofen suspension drops, can not be used once every 4 hours, the specific need to follow the doctor’s advice. Acetaminophen drops and ibuprofen drops are the two most commonly used fever-reducing medications for infants and young children, and can be used for symptomatic treatment of most fevers. If acetaminophen drops are used, they can be used at 4-hour intervals for persistent high fever, but not more than 4 times in 24 hours. If ibuprofen drops are used, they should not be used once every 4 hours, but should be repeated at 6-8 hour intervals, not more than 4 times every 24 hours. It should be noted that three and a half year old baby fever parents in the use of drugs, including antipyretic drugs, should know the specific use of drugs and name, if in doubt consult a doctor in a timely manner, under the guidance of the doctor to use, do not arbitrarily use their own medication. Secondly, the baby fever in addition to symptomatic antipyretic treatment, but also need to consult a doctor in a timely manner, clear cause of fever to give targeted treatment.