High fever in children without symptoms can be caused by a variety of reasons, which can be categorized into environmental heat, infectious factors and non-infectious factors. 1. Environmental heat: For example, in summer, when the weather is hot and the environment is hot, the body temperature may increase due to the decrease of heat dissipation, and the body temperature is usually low and not accompanied by other symptoms. In addition, it can also show less sweat and other clinical symptoms. 2. Infectious factors: when the baby is infected by bacteria, viruses, mycoplasma, chlamydia and other pathogenic microorganisms, in the early stage of the disease can appear fever and not accompanied by any symptoms, with the progress of the disease can appear some accompanying symptoms. 3. other non-infectious factors: baby with leukemia, systemic lupus erythematosus, early in the disease can be manifested as fever, may not be accompanied by other symptoms, with the progress of the disease can appear some accompanying symptoms. Baby fever need to go to the hospital, after a clear diagnosis, targeted treatment, they can not just use drugs.