A bag behind the ear may be caused by physiological factors, enlarged lymph nodes, sebaceous cysts, dermatofibroma and other diseases. If it is caused by infection, you can take anti-inflammatory drugs such as cephalosporin and amoxicillin orally. If it is caused by other factors, it is recommended to target the treatment. 1. Physiological factors: common in childhood babies, the lymph nodes around the ear, can appear transient enlargement. If there is no other discomfort, you can first closely observe, do not recommend blindly give the baby anti-inflammatory drugs. 2. Enlarged lymph nodes: a bag behind the ear, can also be considered an infection caused by enlarged lymph nodes. For example, acute tonsillitis, acute pharyngitis, can involve the lymph nodes behind the ear, resulting in lymph node enlargement. Cefixime, cefprozil, amoxicillin and other anti-infective treatments can be given in combination with the doctor’s advice. 3. Sebaceous cysts: Sebaceous cysts, also called acne, can occur behind the ear and are related to blocked sebaceous gland secretion. It is recommended to make a clear diagnosis. If necessary, the cyst should be completely removed by surgery, and cephalosporin antibiotics such as cefixime should be given after surgery. 4. Dermatofibroma: The lump formed by dermatofibroma cannot subside by taking anti-inflammatory drugs alone, and if necessary, it will be treated by surgical excision under anesthesia. In addition to this, the foci of lymphoma or peripheral tumors metastasize to lymph nodes, resulting in localized lumps behind the ear. If you find a localized mass behind the ear, it is recommended to go to the hospital for examination as soon as possible, which can clarify the cause of the localized mass and standardize the treatment.