The reason for a big one is a small one, the specific analysis is as follows: 1, congenital breast inconsistency, by the genetic decision of the breast size is not the same, if the difference is not large can not be dealt with, if the difference is too large can be surgical plastic surgery. 2, breast pressure, side sleep or one side of the shoulder belt is relatively short resulting in breast pressure, in the development period blood flow is not smooth than the other side of the breast small, change habits can be corrected. 3, breast disease, mastitis or trauma to the breast during the development of the mammary gland, the need to take oral anti-inflammatory drugs to reduce inflammation or spray Yunnan Baiyao aerosol to activate blood circulation and remove blood stasis. Mammary gland hyperplasia, breast fibroids, breast cysts lead to enlargement of the affected side of the breast, if it is not obvious, for mammary gland hyperplasia and breast cysts patients can be observed regularly, otherwise surgery is needed to remove the hard mass, if it is breast fibroids need to arrange surgery to remove the tumor in time.