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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 8/12/2021

Updated by: Todd Campbell, MD, FACS, Clinical Assistant Professor, Department of Surgery, Volunteer Faculty, Rowan University School of Osteopathic Medicine, Stratford, NJ; Medical Director, Independence Blue Cross, Philadelphia, PA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.