The common causes of physiological breast swelling and pain are as follows: 1. The influence of the menstrual cycle: changes in women’s menstrual cycle, accompanied by endocrine fluctuations, can trigger physiological breast swelling and pain. Menstrual cycle in vivo estrogen, progesterone have greater fluctuations, and the target organ is the breast, breast tissue. Therefore, during ovulation and the pre-menstrual period, the estrogen in women’s bodies rises and fluctuates greatly, thus triggering physiological breast swelling and pain; 2.