Swollen lymph nodes behind the ear in adults are mostly considered to be caused by inflammatory or infectious factors. Most of the swollen lymph nodes behind the ear caused by bacterial infection are due to gingivitis, mumps, otitis media, suppurative parotitis, acute tonsillitis, acute lymphadenitis and other related diseases; swollen lymph nodes behind the ear caused by other infections are mostly considered to be caused by herpes zoster, tuberculosis of lymph nodes, rubella and so on. Whether the lymph nodes behind the ear are swollen due to inflammation or infection, the patient may show swollen lymph nodes behind the ear with obvious tenderness when touching, and when the swelling reaches a certain level, the swelling may stop. Adults with swollen lymph nodes behind the ear should go to their local hospitals for early detection and treatment to avoid delays.