A small child with a small bag behind the ear may be related to lymphadenitis behind the ear, purulent otitis media, sebaceous cysts and so on. 1. Post-auricular lymphadenitis: if a child suffers from mumps or otitis externa nearby parts of the inflammation and infection, if involved in the lymph nodes, can also cause local lymph node enlargement, resulting in the occurrence of the situation. 2. Suppurative otitis media: If a child suffers from this disease and is not treated in a timely manner, as the disease progresses, complications such as mastoid subperiosteal abscesses may occur, and there may be a small bag behind the ear. 3. Sebaceous cysts: If the local pores are blocked, then the secretion of oil can not be discharged in a timely manner, in the long run is likely to form prominent sebaceous cysts. As you can see, there are many reasons for children to have small bags behind their ears. Parents should pay attention to whether there are other symptoms in time, so that they can seek medical treatment in time.