The baby has been a bag behind the ear to consider and lymph node enlargement, sebaceous cyst of the skin behind the ear, lymphoma and other diseases related. 1. Enlarged lymph nodes: Lymph nodes are the body’s defense organs. When babies have respiratory infections or potential viral infections, it is easy to cause pain and swelling of the lymph nodes behind the ear. This is manifested by the appearance of a bag behind the ear. 2. Sebaceous cysts of the skin behind the ear: when the sebaceous glands of the skin behind the ear are blocked, it can lead to sebaceous adenitis, resulting in the appearance of a single bag behind the baby’s ear. At this time, you should pay attention to the cleanliness and hygiene of the skin, do not squeeze the affected area, so as not to aggravate the symptoms. 3. Lymphoma: When lymphoma occurs, it can lead to the gradual enlargement of lymph nodes in a short period of time, resulting in the appearance of lumps behind the ears of babies. At the same time, there will be recurrent fever, body weakness and other systemic symptoms. If the symptoms of small bags behind the ear continue to not subside, it is recommended to consult a doctor in time to clarify the cause of the disease, so as to facilitate the treatment of the cause.