Underarm pain and swelling are often caused by the following reasons: First, skin infection, when the skin infection in the armpit is more serious, there will be pain and swelling, you need to go to the hospital to apply drugs for treatment, but also need to take oral antibiotics for treatment. Second, the axillary growth of swelling caused by, for example, sebaceous cysts or fibroids, need to check the ultrasound for clarification. If it is one of these diseases, it needs to be removed surgically under anesthesia. Thirdly, swollen lymph nodes can be caused by many reasons, such as bacterial infection, viral infection, tuberculosis infection, autoimmune system disease, blood system disease, etc. Further improvement of other tests is needed to clarify. Fourth, some patients are caused by parametrial hyperplasia, which is common in women during pregnancy and postpartum, and can be clarified by ultrasound.