The baby has a fever in the early morning but is fine during the day because: 1, the child will be attracted by things outside or other activities of interest during the day, so his reaction can be suppressed, such as the fever reaction will not be so obvious, wait until the child’s brain is at rest after going to sleep, which can make his own suppressed reaction slowly manifest, so the child is fine during the day and has a fever at night, and sometimes the temperature is higher at night. 2. if the child itself is already sick, not in good spirits, sleeps for a long time, and the child does not drink water at night, the body temperature will slowly increase. 3. because the air is not circulating at night and the windows are closed, the child will also have the symptoms of being fine during the day and having a fever in the early morning. 4. in Chinese medicine theory, the yang energy of a person will slowly increase after 11 p.m., resulting in a fever starting from 11 p.m. onwards. This phenomenon can be explained in the theory of Chinese medicine.