There are many reasons why one breast has milk and the other doesn’t, which are analyzed as follows: 1. Improper breastfeeding, the production of milk is not only stimulated by lactogen, but also by the baby’s sucking action. It is possible that the baby often sucks on one side of the breast, resulting in the other side of the stimulus is small, so the secretion of milk will be less. You can change the way of breastfeeding, let the baby suck on both sides, you can also use a breast pump to suck on the breast that has no milk, to promote milk secretion. At the same time, eat more food with high protein content to promote milk secretion. 2, milk stagnation, unilateral nipple deformity or inversion or distortion of the milk ducts, resulting in the production of milk has no way to discharge, are gathered in the breast, a long time the breast will be swollen pain. If bacteria enter, pus will be produced, forming mastitis, you can massage, physical therapy, or use a breast pump to promote the discharge of milk.