Why does my baby have a fever at night but is fine during the day?

It is a relatively common situation for a baby to have a fever at night while having a normal temperature during the day. Below are several possible causes: 1. **Circadian rhythm variations**: A baby's body temperature is influenced by circadian rhythms, and temperature may be higher in the evening. This natural fluctuation can sometimes result in nighttime fever with normal daytime temperatures. 2. **Types of infection**: Certain infections, such as upper respiratory tract infections or viral infections, may worsen in the evening, leading to fever. Symptoms may be milder during the day, resulting in a normal body temperature. 3. **Inflammatory responses**: Some inflammatory or immune responses may intensify at night, causing fever. For example, periodic fluctuations in the body's inflammatory response or infection may be more pronounced in the evening. If the baby's fever persists or is accompanied by other severe symptoms, medical attention should be sought promptly.