Weaning two and a half months left breast swelling and pain may be caused by physiological factors, may also be caused by pathological factors such as breast hyperplasia, mastitis. 1. physiological factors: the mother will produce milk for a long time after the birth, if it is the early stage of weaning, such as a few months after the birth of the weaning, then the secretion of milk will be more. If the milk cannot be discharged, you can use a breast pump to suck out the milk, which will ease the pain. 2. Pathologic factors: (1) Breast hyperplasia: Slight pain in the breasts after two and a half months of weaning cannot be ruled out as breast hyperplasia. Breast enlargement and menstruation have a certain connection, may appear before the symptoms of menstruation, after menstruation pain will be reduced. (2) Mastitis: If mastitis is caused by milk stagnation and bacterial infection, the inflammation stimulation will produce pain accompanied by redness, swelling, heat and pain in the breasts, and even generalized fever. In addition, mammary gland trauma, breast cancer, breast cysts may also appear similar clinical manifestations, if the weaning of two and a half months of the left breast swelling and pain symptoms, persistent and unrelieved, you need to consult a doctor in time for treatment.