Mastitis is an acute purulent infection of the mammary glands, a common condition in the puerperium and one of the causes of postpartum fever, most commonly in breastfeeding women, especially first-time mothers. It can occur at any time during the lactation period and is most common at the beginning of breastfeeding. The cause of mastitis 1, the stagnation of milk: the stagnation of milk is conducive to the growth and reproduction of invading bacteria. The causes are: (1) small or invaginated nipples, preventing breastfeeding, pregnant women fail to correct invaginated nipples in time before delivery, infants have difficulty sucking milk; (2) too much milk, incomplete emptying, the mother did not empty the excess milk in the breast in time. (3) The milk ducts are inaccessible, the milk ducts themselves are inflamed, tumors and external pressure, and the fibers shed from the bra can also block the milk ducts. 2, the invasion of bacteria: nipple inversion when the baby sucking difficulties, easy to cause the nipple around the breakage, is the main way of bacteria along the lymphatic invasion caused by infection. In addition, infants often sleep with nipples, but also can make the infant oral inflammation directly invade and spread to the milk ducts, and then spread to the interstitial mammary glands to cause purulent infection. Staphylococcus aureus is the common causative organism.