One side of the breast swelling pain in a variety of diseases, mainly including: first, acute mastitis, common in lactating women, the main cause of bacteria through the cracked nipple infection of the breast tissue, causing acute purulent infectious lesions of the breast. In the early stage of infection, when one side of the breast is swollen and painful or the local skin temperature of one side of the breast is increased, the breast should be emptied and given penicillin or cephalosporin anti-infective treatment, most of them can be cured, and the infection is further aggravated by the formation of mammary abscess, which needs to be carried out by mammary abscess incision and drainage surgery. Second, breast hyperplasia, endocrine hormone disorders caused by excessive breast hyperplasia and incomplete regeneration, clinical manifestations of breast swelling and pain with breast hyperplasia nodule formation, and the nature of pain and nodule size is related to the changes of menstrual cycle, if the symptoms are not obvious, can be given medication for conservative treatment. Third, mammary gland trauma, most of them have obvious trauma history and localized breast bruise, can be given to reduce swelling, pain relief and other symptomatic treatment.