Swelling of the flesh behind a posterior alveolar tooth may be due to wisdom tooth pericoronitis, periodontal abscess, alveolar abscess etc. It needs rinsing and medication, abscess incision or puncture drainage, periodontal treatment, root canal treatment and so on. 1. Wisdom tooth pericoronitis: mainly local symptomatic treatment, rinsing, saline and hydrogen peroxide alternately, with topical iodine glycerin local application. 2. Periodontal abscess: the abscess is incised or punctured and drained, followed by periodontal treatment. 3. Alveolar abscess: incise or puncture the abscess for drainage, followed by root canal treatment. It is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.