Postpartum mastitis occurs sporadically in nursing mothers shortly after they return home, or it may occur in epidemic form in the hospital. Staphylococcus aureus is usually the causative agent. Inflammation is generally unilateral, and women nursing for the first time are more often affected. Rarely, inflammatory carcinoma of the breast can be mistaken for puerperal mastitis.

Mastitis frequently begins within 3 months after delivery and may start with a sore or fissured nipple. There is obvious cellulitis in an area of breast tissue, with redness, tenderness, local warmth, and fever. Treatment consists of antibiotics effective against penicillin-resistant staphylococci (dicloxacillin or a cephalosporin, 500 mg orally every 6 hours for 5-7 days) and regular emptying of the breast by nursing followed by expression of any remaining milk by hand or with a mechanical suction device.

If the mother begins antibiotic therapy before suppuration begins, infection can usually be controlled in 24 hours. If delay is permitted, breast abscess can result. Incision and drainage are required for abscess formation. Despite puerperal mastitis, the baby usually thrives without prophylactic antimicrobial therapy.