Breast infection

Alternative names
Mastitis; Infection - breast tissue; Breast abscess

This infection is located in the tissue of the breast. In most cases, bacteria entered the tissue through cracks in the nipples.

Causes, incidence, and risk factors

Breast infections are usually caused by a common bacteria found on normal skin (Staphylococcus aureus). The bacteria enter through a break or crack in the skin, usually the nipple.

The infection then takes place in the parenchymal (fatty) tissue and causes swelling of the parenchymal tissue outside the milk ducts. This swelling compresses on the milk ducts, and the result is pain and swelling of the infected breast.

Breast infections usually occur in women who are breast-feeding. Breast infections that are not related to breast-feeding must be differentiated from a rare form of breast cancer.


  • breast pain  
  • breast lump  
  • breast enlargement on one side only  
  • swelling, tenderness, redness, and heat in breast tissue  
  • nipple discharge (may contain pus)  
  • nipple sensation changes  
  • itching  
  • tender and/or enlarged lymph nodes in armpit on the same side  
  • fever

Signs and tests

In women who are not breast-feeding, testing may include mammography or breast biopsy. Otherwise, tests are usually not necessary.


Self-care may include applying moist heat to the infected breast tissue for 15 to 20 minutes four times a day.

Antibiotic medications are usually very effective in treating mastitis. You are encouraged to continue to breast-feed or to pump to alleviate engorgement while receiving treatment.

Support Groups

The stress of an illness can often be helped by joining a support group in which members share common experiences and problems. See breast-feeding - support group.

Expectations (prognosis)

The condition usually clears quickly with antibiotic therapy.


In severe infections, an abscess may develop. Abscesses require more extensive treatment, including incision and drainage. Discontinuation of breast-feeding may be recommended in this case.

Calling your health care provider

Call your health care provider if any portion of the breast tissue becomes reddened, tender, swollen, or hot, or if the lymph nodes in the armpit become tender and/or enlarged.


Good breast care, especially after delivery and while breast-feeding, may decrease the potential to develop breast infections.

Johns Hopkins patient information

Last revised: December 8, 2012
by Armen E. Martirosyan, M.D.

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