The main causes of nipple swelling and discomfort can include the following: 1, due to the impact of breast enlargement, in most cases breast enlargement, will be manifested as breast swelling and discomfort, some patients will be confined to the nipple, the pain is more obvious before the onset of menstruation. 2, there may be a reaction to inflammation of the breast, when there is inflammation of the breast, there will be local pain and discomfort, especially the nipple The pain is more obvious. It is easy to ignore the possible reaction of pregnancy, the first reaction of the body may be in the breast and even the pain of the nipple.