A breast infection is an infection in the tissue of the breast.

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 takes place in the parenchymal (fatty) tissue of the breast and causes swelling. This swelling pushes on the milk ducts. 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 distinguished from a rare form of breast cancer.

• Breast pain
• Breast lump
• Breast enlargement on one side only
• Swelling, tenderness, redness, and warmth in breast tissue
• Nipple discharge (may contain pus)
• Nipple sensation changes
• Itching
• Tender or enlarged lymph nodes in armpit on the same side
• Fever

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