Baby’s sudden high fever may be due to infectious fever caused by bacteria, virus, or caused by blood system diseases, it is recommended to consult a doctor in time. 1. Infectious fever: due to the baby’s own immune system is not well developed, low resistance, once exposed to bacteria, viruses, etc., easy to cause upper respiratory tract infections and other diseases, resulting in a sudden high fever. To timely cooling treatment, but also closely observe the baby’s mental state, if the temperature continues to rise and the baby’s mental state is not good, we must promptly seek medical attention. 2. Blood system diseases: such as leukemia or some malignant tumors, sometimes also cause the baby suddenly high fever, when the general anti-infection treatment is ineffective, and there will be increased blood or platelet changes. If the baby suddenly high fever, must promptly consult a doctor for relevant examination, clear cause of the cause of treatment, so as not to delay the condition.