Enlarged lymph nodes behind the ear in infants and young children may be caused by local inflammation, blood diseases and other causes of lymph node enlargement. 1. Local inflammation: lymph nodes belong to peripheral immune organs, when there are bacteria, viruses and other infections, triggering acute inflammation of the body, invading the lymph nodes behind the ear, which can cause lymph nodes behind the ear to become enlarged and painful. 2. Blood diseases: If the lymph nodes behind the ear and the lymph nodes in the neck are enlarged, and the degree of swelling is more serious, and the lymph nodes are adhered to the surrounding skin, then we need to be vigilant about blood diseases, such as malignant lymphoma, leukemia and so on. There may be other reasons for the swelling of lymph nodes behind the ears of infants and young children, it is recommended to go to the hospital in time, complete the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.