Sudden swelling of the cheeks under the ears may be caused by mumps, enlarged lymph nodes or wisdom teeth pericoronitis. 1. Mumps: Generally, it is considered that mumps caused by bacteria or virus, with swelling and pain under one or both earlobes, heat and redness on the surface, accompanied by fever, fatigue and other systemic manifestations. 2. Enlarged lymph nodes: often caused by bacterial infection or viral infection, which may be manifested as localized enlarged lymph nodes with tenderness, soft texture and no adhesion. The surrounding tissues may have redness, heat and pressure pain. 3. Wisdom tooth pericoronitis: If mandibular wisdom teeth cause pericoronitis, pericoronitis can easily cause infections in neighboring spaces, including occlusal space infection, pterygomandibular space infection, which can be manifested as swelling and pain in the cheeks. If the above symptoms occur, it is recommended to go to the hospital in time for early formal treatment.