There are many reasons for breast swelling and pain, such as breast development, before menstruation, breast hyperplasia, breast cancer, etc. Patients are advised to go to the hospital for checkups, and if it is a disease, it should be treated promptly. 1. Breast development: When a girl’s breasts develop during puberty, it may cause swelling and pain in both breasts. If this is the case, there is no need to worry too much, after puberty, most of the symptoms will disappear. 2. Before menstruation: The increase of estrogen level in women’s body before menstruation, breast hyperplasia, and edema of intermammary tissues may cause swelling and pain in both breasts. After menstruation, the symptoms of breast swelling and pain will be relieved. 3. Breast Hyperplasia: When women’s endocrine hormone imbalance, as the breast is more sensitive to hormone changes, it may cause breast tissue hyperplasia, which leads to breast swelling and pain, it is recommended that the patient go to the hospital for detailed examination to regulate the body’s hormones. 4. Breast cancer: Breast cancer with inflammation may be accompanied by breast swelling and pain, usually on one side but also on both sides. It can also be accompanied by other symptoms such as nipple indentation, breast lumps and so on. Therefore, it is recommended to go to the hospital for detailed examination when the patient has breast swelling and pain. If it is physiological condition, usually no treatment is needed, but if it is pathological condition, it is better to treat it in time to avoid deterioration of the condition.