The left side of the headache of a five-year-old child will be fine for a while, it may be caused by eye fatigue, lack of sleep, trauma and other reasons. 1. Eye fatigue: children usually write homework, watch TV dramas with more eyes, easy to cause eye fatigue, eye muscle contraction activity is more intense, thus appearing headache symptoms, after appropriate rest, headache symptoms can be gradually relieved. 2. Lack of sleep: Lack of sleep can make the brain fatigue, leading to lack of oxygen in the brain, cerebral vascular spasm, which leads to headache, the child after proper rest, headache symptoms can be improved. 3. Trauma: A fall or some other external causes can easily cause a child’s head to be injured, resulting in headaches, after a certain period of time. If your child suffers from frequent headaches, it is recommended to go to the hospital for a corresponding brain examination to clarify whether he or she is suffering from a certain disease and follow the doctor’s instructions for treatment.