Acute mastitis is an acute suppurative infection of the breast. It is an inflammation of the connective tissue in and around the mammary ducts. It often forms an abscess in a short period of time. It is mostly caused by the invasion of Staphylococcus aureus or Streptococcus along the lymphatic vessels. It often occurs in women who are breastfeeding after childbirth, especially primiparas. The bacteria usually invade from the cracks or fissures of the nipples, or they can directly invade and cause infection. Literature reports that 50% of primiparas suffer from acute mastitis, and the ratio of primiparas to multiparas is 2.4:1. It can occur at any time during the lactation period, but it is most common 3 to 4 weeks after delivery, so it is also called puerperal mastitis.