Swelling behind the ear is clinically possible as follows: 1. Inflammation of the lymph nodes behind the ear is clinically more common. The primary focus may be an infection of the ear canal or throat, and the inflammation spreads to the lymph nodes behind the ear resulting in swelling of the lymph nodes. The lymph node swelling will gradually subside after the inflammation is controlled. 2. Infection of the postauricular chalk tumor, which occurs in patients who are obese and often eat greasy food. The secretion of sebaceous cyst behind the ear is blocked and the local infection leads to swelling, which requires anti-inflammatory treatment at the hospital. If the local fluctuating sensation suggests abscess formation, incision and drainage treatment is also required.3. Some children with acute mastoiditis presenting with swelling behind the ear need to have a middle ear mastoid CT examination to confirm the diagnosis.