Recurrent fever for four days in children is an abnormal phenomenon, which may be related to bacterial infection, viral infection, infectious diseases, autoimmune diseases and other factors. 1. Bacterial infection: after bacteria invade the body, it will lead to the body’s immune response and fever symptoms, and when it is not effectively treated, the symptoms of recurrent fever may occur, and the common diseases are urinary tract infection, pneumonia and so on. 2. Viral infections: viral infections can also cause an immune response, resulting in recurrent fever symptoms, common diseases include influenza, colds and so on. 3. Infectious diseases: Malaria and other infectious diseases can cause recurrent fever symptoms, and need timely isolation and treatment. 4. Autoimmune diseases: such as Kawasaki disease, is a skin and mucous membrane lymph node syndrome, part of which can involve the heart, will also be manifested in more than five days of recurrent fever, and mainly high fever, antibiotic treatment is basically ineffective. The disease can present with atypical symptoms and requires evaluation and judgment by a medical professional. Children with recurring fever for four days should go to the hospital in a timely manner to identify the cause of the disease and then carry out the relevant treatment as far as possible.