There are several different causes of breast fever during breastfeeding: first, consider the occurrence of mastitis, breastfeeding women produce more milk, if the milk gathered in the breast can not be eliminated will lead to mastitis, thus appearing breast fever, swelling and pain, will have an impact on the body, it is best to timely treatment. Secondly, it may be that the nipple ruptures due to frequent sucking of the nipple by the baby during breastfeeding, and bacteria or viruses enter the breast and cause symptoms of infection, and other complications, such as pus, destruction of breast tissue, and also fever. Once acute mastitis occurs it can lead to more serious disease, it is best to temporarily stop breastfeeding, use anti-inflammatory drugs for treatment, and pay attention to good health care during breastfeeding to avoid disease reactions.