Acute mastitis is an acute purulent infection of the breast, an inflammation of the connective tissue in and around the ducts of the breast. The main causes are bacterial invasion, milk stasis, nipple cracking, and decreased immunity. Prevention: 1, the key is to prevent the stagnation of milk, while avoiding nipple injury, and keep the local clean (warm water can be cleaned). 2, to develop regular breastfeeding, the baby does not contain the nipple and sleep and other good breastfeeding habits. 3.Every time you breastfeed, you should empty the milk. If there is stagnation, you can use a breast pump or massage to help empty the milk. 4.The nipples should be washed after breastfeeding. 5.If you find that your nipple is broken or ruptured, you should treat it promptly. 6. Pay attention to the oral hygiene of the baby and treat its oral inflammation in time.