The child’s fever will be feverish for a while, which means that the type of fever is intermittent fever, regression fever or irregular fever, which may be caused by infections, rheumatic diseases or tumors. 1. Intermittent fever: the body temperature rises suddenly to the peak and lasts for a few hours, after which it returns to normal rapidly. The fever-free period can last for a few days, and the fever alternates with the fever-free period, so it is called intermittent fever, which can be seen in malaria, acute pyelonephritis and lymphoma. 2. Regression fever: the body temperature rises abruptly to 39°C or above, and then drops to normal abruptly after a few days, and the fever-free period may last for a few days, and the period of fever alternates with the period of fever-free period regularly, which is called undulating fever, and it can be seen in regression fever leptospirosis and Hodgkin’s tumor. 3. Irregular fever: the fluctuation of body temperature during fever has no obvious regularity, which is called irregular fever and has the most reasons, such as upper respiratory tract infection, bronchopneumonia, mycobacterium tuberculosis infection, rheumatic fever and malignant tumor. There may be other reasons why your child’s fever may or may not fluctuate, so it is recommended that you go to the hospital in a timely manner, complete the examination to determine the cause of the illness, and then give targeted treatment under the guidance of the doctor.