The breast is composed of several glands and ducts that lead to the nipple and the surrounding colored area called the areola. The milk-carrying ducts extend from the nipple into the underlying breasttissue like the spokes of a wheel. Under the areola are lactiferous ducts. These fill with milk during lactation after a woman has a baby. When a girl reaches puberty, changing hormones cause the ducts to grow and cause fat deposits in the breast tissue to increase. The glands that produce milk (mammary glands) that are connected to the surface of the breast by the lactiferous ducts may extend to the armpit area.
Mastitis is an infection of the tissue of the breast that occurs most frequently during the time of breastfeeding. It can occur when bacteria, often from the baby's mouth, enter a milk duct through a crack in the nipple.
Breast infections most commonly occur one to three months after the delivery of a baby, but they can occur in women who have not recently delivered and in women after menopause. Other causes of infection include chronic mastitis and a rare form of cancer called inflammatory carcinoma.
In healthy women, mastitis is rare. However, women with diabetes, chronic illness, AIDS, or an impaired immune system may be more susceptible.
About 1%-3% of breastfeeding mothers develop mastitis. Engorgement and incomplete breast emptying can contribute to the problem and make the symptoms worse.
Chronic mastitis occurs in women who are not breastfeeding. In postmenopausal women, breast infections may be associated with chronic inflammation of the ducts below the nipple. Hormonal changes in the body can cause the milk ducts to become clogged with dead skin cells and debris. These clogged ducts make the breast more open to bacterial infection. Infection tends to come back after treatment with antibiotics.
Breast infections may cause pain, redness, and warmth of the breast along with the following symptoms: