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 breast tissue 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 as well as 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 Infection Symptoms
Breast infections may cause pain, redness, and warmth of the breast along with the following symptoms:
Tenderness and swelling
Fever and chills
Abscess: Sometimes a breast abscess can complicate mastitis. Noncancerous masses such as abscesses are more often tender and frequently feel mobile beneath the skin. The edge of the mass is usually regular and well defined. Indications that this more serious infection has occurred include the following:
Tender lump in the breast that does not get smaller after breastfeeding a newborn (If the abscess is deep in the breast, you may not be able to feel it.)
Pus draining from the nipple
Persistent fever and no improvement of symptoms within 48-72 hours of treatment
When to Seek Medical Care
Call your health care provider as soon as you feel any suspicious lump, whether you are breastfeeding or not. Call for an appointment if:
You have any abnormal discharge from your nipples.
Breast pain is making it difficult for you to function each day.
You have prolonged, unexplained breast pain.
You have any other associated symptoms such as redness, swelling, pain that interferes with breastfeeding, a mass or tender lump in the breast that does not disappear after breastfeeding.
If you are breastfeeding, call your doctor if you develop any symptoms of breast infection so that treatment may be started promptly.
You may need to be evaluated in a hospital's emergency department if the breast pain is associated with other signs of an infection (such as a fever, swelling, or redness to the breast) and if your health care provider cannot see you promptly. The below symptoms require emergency treatment:
A persistent high fever greater than 101.5°F
Nausea or vomiting that is preventing you from taking the antibiotics as prescribed