Buns behind the ear are painless and itchy and may be caused by sebaceous cysts, enlarged lymph nodes, malignant lymphoma, or mastoid process. 1. Sebaceous cyst: Due to the accumulation of secretion caused by the blockage of sebaceous glands behind the ear, a cyst may appear and is painless and itchy. 2. Enlarged lymph nodes: When the lymph nodes behind the ear are enlarged in size, a lump may be seen directly and there may be no pain or itching. 3. Malignant lymphoma: If you have malignant lymphoma, the enlarged lymph nodes are often painless, tough and smooth, and are not accompanied by itching symptoms. 4. Mastoid: Mastoid is located behind the ear, showing a cone-like protrusion, slightly above the skin. It is recommended to go to the regular hospital in time to clarify the cause of the disease and carry out standardized treatment under the guidance of the doctor.