There is one side of the chest pain usually consider the following aspects: First, it is possible that the estrogen level in the body of women before and during menstruation is constantly changing with the menstrual cycle, the level is higher, the mammary gland under the effect of pain, swelling and pain, most menstruating women have such symptoms, but with the end of menstruation will disappear. The second aspect is mastitis, which occurs mainly in breastfeeding women, mostly due to the accumulation of milk in the mammary glands due to the lack of timely breastfeeding, or the lack of thorough cleaning and hygiene, and the retrograde infection of bacteria in the nipples, leading to mastitis. The third aspect is the presence of breast tumors or breast lumps, accompanied by unevenness of the breast skin or discharge. Fourthly, it may be caused by improperly fitting underwear or trauma.