If a child has low white blood cells and low lymphocytes along with fever, it may be due to immune system disorders, blood system disorders, and drug effects. It is recommended to bring the child to the doctor in time to clarify the specific causes through relevant examinations, and then carry out targeted treatment according to the causes.1. Immune system diseases: For example, systemic lupus erythematosus, which is an autoimmune inflammatory connective tissue disease that can accumulate to multiple organs, children will have fever due to inflammatory reactions, and low white blood cells and low lymphocytes due to white blood cell depletion, which can be Azathioprine tablets, cyclosporine soft capsules, compound cyclophosphamide tablets, tacrolimus capsules, methotrexate tablets and other drugs are given for treatment; 2. Hematologic disorders: for example, aplastic anemia, due to bone marrow hematopoietic dysfunction, and can not produce enough blood cells as well as white blood cells, resulting in low white blood cell count and low lymphocytes in children with fever. Immunosuppressants can be given for treatment, such as cyclosporine soft capsule, compound cyclophosphamide tablets, etc., and then give hematopoietic factors, such as recombinant human platelet generating factor injection, to reduce the chance of infection, for heavy aplastic anemia can be treated with hematopoietic stem cell transplantation; 3, drug effects: If the child applies certain drugs when fever, such as ibuprofen granules, acetaminophen suspension drops and other antipyretic If a child is exposed to radiation, it may damage the function of the bone marrow to produce white blood cells and lymphocytes, which may result in low white blood cells and lymphocytes. It is necessary to stay away from radiation and then check whether the bone marrow function can be restored. In addition, if a child is in the acute phase of an infectious disease, there may be a decrease in leukocytes and lymphocytes due to depletion, which usually recovers when the disease improves. Therefore, if a child has low white blood cells and lymphocytes along with a fever, he or she should be seen in the hospital promptly rather than immediately using cooling medications that may affect the diagnosis and treatment of the disease. During the treatment period, it is important to ensure that the child gets enough rest and sleep, and that the diet is light and nutritious, which can promote the improvement of the disease.