There are more reasons for breast swelling, according to the different diseases that cause breast swelling, the reasons are mainly divided into the following cases: First, the normal growth and development of the breast during puberty, both men and women may have some degree of breast swelling or pain, which is a normal phenomenon does not require treatment. Second, lactating women, due to the normal lactation needs and even milk accumulation, the breast will have a certain degree of swelling, need to do a good job of breast care, to prevent acute mastitis. Third, before the onset of menstruation, the body’s estrogen level rises to stimulate the breast swelling, generally after the end of menstruation when estrogen levels return to normal, the swelling will resume. Fourth, mild mastocytosis will have a swollen feeling in the breast area due to an abnormally high level of estrogen in the body. Fifth, benign tumors and cysts in the breast area, such as breast fibroids and breast cysts, will cause swelling and discomfort in the breast due to the enlargement of the mass. Sixth, malignant tumors of the breast, malignant tumors do not have obvious pain in the early stage, but can appear discomfort in the breast area, some people manifest as swelling.