Acute mastitis is an acute inflammation of the breast that occurs during breastfeeding, mainly due to local blockage of milk causing hard knots and local inflammation caused by bacteria entering through the nipple. Acute mastitis usually starts with mild inflammation, no redness or swelling of the skin, only blockage of milk, and a low temperature, which can be gradually improved by sucking or lactation. If there is local redness, swelling, fever and elevated leukocyte index, antibacterial treatment is needed. After the inflammation is controlled, the body temperature can gradually decrease and the local hard nodes will disappear. If, after anti-inflammatory treatment, localized pus formation is aggravated and the body temperature does not decrease, puncture or local incision is needed to drain the pus.