Breast abscess - Causes of a breast abscess
NHS Choices Medical Reference
Most breast abscesses occur as a complication of mastitis, a bacterial infection that causes the breast to become red and inflamed.
Mastitis usually affects breastfeeding women, but it can sometimes occur in women who are not breastfeeding.
Women who smoke cigarettes have an increased risk of developing non-breastfeeding mastitis. This condition is known as periductal mastitis.
Most abscesses are caused by a bacterial infection. The bacteria usually enter the breast through small cracks or breaks in the skin of the nipple, which can sometimes develop during breastfeeding.
Infections can also be caused by an overgrowth of bacteria that usually exist quite harmlessly within the milk ducts (the tiny tubes inside the breast that carry milk). An overgrowth of bacteria can occur if stagnant milk collects in a blocked milk duct.
When bacteria enter your body, your immune system (the body's natural defence) tries to fight them off by sending white blood cells to the affected area. As the white blood cells attack the bacteria, some of the tissue at the site of the infection dies, creating a small, hollow pocket.
The pocket starts to fill with pus, forming an abscess. The pus contains a mixture of dead tissue, white blood cells and bacteria. As the infection progresses, the abscess may get bigger and more painful as more pus is produced.