The causes of pain behind the left ear, including inflammatory diseases, sebaceous cysts, neuralgia, etc., are as follows: First, inflammatory diseases: common acute otitis externa, otitis externa boils, acute mastoiditis, acute suppurative otitis media, and other related diseases, which can cause patients to have pain behind the ear. Some patients who have parotid inflammation can also experience pain in this area. The more serious the inflammatory infection, the more obvious the pain may be. Second, sebaceous cysts: some patients have something behind the ear, such as sebaceous cyst infection behind the ear, can appear local pain. When the cyst breaks, the pain may be reduced, but usually accompanied by localized pus and other related symptoms. Clinical need to increase anti-inflammatory anti-inflammatory treatment, may need to do surgical debridement. Third, neuralgia: some patients have neuralgia behind the ear, neuralgia may be related to the patient’s fire, stay up all night and other triggers, mostly manifested as intermittent throbbing pain.