DefinitionA breast infection is an infection in the tissue of the breast.Alternative NamesMastitis; Infection - breast tissue; Breast abscessCauses, incidence, and risk factorsBreast infections are usually caused by a common bacteria (Staphylococcus aureus) found on normal skin. The bacteria enter through a break or crack in the skin, usually on the nipple.The infection takes place in the fatty tissue of the breast and causes swelling. This swelling pushes on the milk ducts. The result is pain and lumps in the infected breast.Breast infections usually occur in women who are breast-feeding. Breast infections that are not related to breast-feeding might be a rare form of breast cancer.SymptomsBreast enlargement on one side onlyBreast lumpBreast painFever and flu-like symptoms including nause