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Mastitis is inflammation of the breast, most commonly due to infection. Mastitis usually occurs in breastfeeding women if milk ducts are blocked, and milk cannot flow out. Bacteria can enter through a duct opening or a crack in the skin of the nipple, and multiply in the milk. Symptoms of mastitis include breast pain, swelling, warmth, and redness.

Review Date 10/10/2022

Updated by: Jonas DeMuro, MD, Diplomate of the American Board of Surgery with added Qualifications in Surgical Critical Care, Assistant Professor of Surgery, Renaissance School of Medicine, Stony Brook, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.