There are many possibilities for a bag on the shoulder. Patients need to go to the hospital, under the examination of professional doctors, according to the size of the bag, the degree of hardness and softness, as well as pain and other performance to clarify the cause: 1, mosquito bites: If the patient has a bag on the shoulder, there is no pain, but only an itchy feeling, it is considered to be caused by mosquito bites. At this time, the patient can use stove glycolic lotion for local itching, external anti-allergy can be used Wuji cream, fluorine easy ointment, etc.; 2, allergy: the patient has a bag on the shoulder, accompanied by other parts of the body appear in different shapes and sizes of the bag as well as red spots, and there is a feeling of intense itching, judged as an allergic reaction. Patients are advised to undergo anti-allergy medication under the guidance of a professional doctor, including loratadine, benadryl, paracetamol, etc.; 3. Folliculitis: If a patient has a bag on the shoulder that shows redness, swelling, heat, painful phenomenon and hard nodules when touched, it is diagnosed as folliculitis. Antibiotic ointment, such as mupirocin ointment, erythromycin ointment, fusidic acid ointment, etc., can be applied under the guidance of a doctor to control and avoid the expansion of inflammation. If more serious folliculitis occurs, it is recommended to visit the hospital as soon as possible and oral antibiotics can be considered; 4. Lipoma and fibroma: They are common benign skin tumors. The difference between the two is the texture, lipoma is softer and fibroma is harder. Patients need to go to the hospital to be palpated by professional doctors, as well as after the color photo examination, to clarify the size, cystic nature and blood circulation of the swelling and determine whether it needs to be surgically removed; 5. Sebaceous cysts: due to the high secretion of sebaceous glands, resulting in the blockage of pores to form cysts. In the area of sebaceous cysts, patients will experience redness, swelling, pain, and in severe cases, the possibility of complications of infection. Patients need to go to the hospital to remove the cysts through local anesthesia surgery; 6. Lymph nodes: there is a possibility that the swollen lymph nodes are caused by infection. Patients need to go to the hospital to identify the primary focus of infection and to develop an anti-infection treatment plan. If the lymph nodes are not eliminated after treatment, pathological biopsy is needed to clarify whether they are caused by tumors if necessary; 7. Aseptic inflammation: the patient’s muscles, ligaments and fascia, under the influence of cold, involvement, trauma and other conditions, lead to local tissue hypertrophy, and the appearance is shown as bags. In this case, cold compresses can be applied to relieve the swelling, and then hot compresses can be applied to promote tissue absorption. In summary, when a patient has a bag on the shoulder and the cause is unknown, he or she needs to be seen in a hospital. After the doctor’s palpation, as well as local ultrasound and color ultrasound, pathological biopsy is needed to clarify the cause if necessary, and a treatment plan is formulated according to the different conditions.