A 7-month-old baby who has a low fever all the time may be caused by bacterial or viral infection, overdressing and food accumulation. 1. Bacterial or viral infections: babies with low fever all the time may be caused by bacterial or viral infections such as inflammation of the upper respiratory tract, acute gastroenteritis or even tuberculosis, which may lead to babies with low fever all the time. 2. Overdressing: The nerve center of the brain of a few months old baby is still not well developed, when the child is overdressed, it is easy to cause the skin temperature to rise, and thus the symptoms of low fever all the time. 3. Accumulation of food: some babies usually eat more, the gastrointestinal tract can not be digested in a timely manner, which led to the child appeared to accumulate food fever symptoms. Parents are advised to take good care of their children and bring them to the hospital as soon as possible to find out the cause if they have persistent low-grade fever.