How does 6 months darling have a fever suddenly to do

6 months baby sudden fever first to clear the cause of fever, for unknown reasons, to take the child to the hospital to do a series of blood tests. For clear cause, to see the child fever temperature, if in 38.5℃ below, take some physical cooling methods can be. If the temperature is above 38.5 ℃, it is necessary to timely give the child to use antipyretic.