Mastitis: Symptoms & Signs

Mastitis is an inflammation of the breast tissue, most often caused by an infection. Mastitis is most common in lactating women. Symptoms include a hard, firm area in the breast that is usually painful. Other symptoms include

  • warmth or redness of the overlying skin,
  • pain in the nipple area, and
  • swelling.

Pain while breastfeeding, fever, chills, and generally feeling unwell (malaise or fatigue) can be other symptoms of mastitis. Sometimes, blood or pus can be seen in breast milk when mastitis is present.

Causes of mastitis

Mastitis is usually the result of a bacterial infection. The bacteria typically enter the breast tissue through a cracked nipple that had developed during breastfeeding. Whether skipping breastfeeding or pumping, allowing milk to become trapped in the breast (engorgement) can increase the risk of mastitis.


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.

Miller, Andrew C. "Mastitis Empiric Therapy." Apr. 10, 2017. <>.

Medically Reviewed by a Doctor on 5/15/2017

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