Mastitis is painful swelling and redness in the breast. It is most common among women who are breastfeeding. It usually occurs in one breast at a time, but it can occur in both breasts at the same time.
Mastitis can occur in women who are not breastfeeding. However, this fact sheet will focus on symptoms and treatment of mastitis that occurs with breastfeeding.
Mastitis is often caused by breast milk trapped in a milk duct. The trapped breast milk can irritate the tissue around it and cause swelling and pain.
Mastitis can also be caused by bacteria. The bacteria can enter the breast through the milk duct or cracks in the skin of nipple. Once the bacteria enter the tissue, it can grow and cause an infection.
Factors that may increase your chances of mastitis:
Abrasion or cracking of the breast nipple
Yeast infection of the breast
Pressure on the breasts, caused by:
Wearing a bra or clothing that is too tight
Sleeping on the stomach
Holding the breast too tightly during feeding
Baby sleeping on the breast
Exercising, especially running, without a support bra
Carrying a bag with a cross chest strap
Anything that causes too much milk to remain in the breast, including:
Missed breastfeeding, which may cause swelling of the breast
Use of supplemental bottle feeds
Incorrect positioning of the baby during feedings
Mastitis may cause:
Redness, tenderness, or swelling of the breast
Aches, chills, or other flu-like symptoms
A burning feeling in the breast
A hard feeling or tender lump in the breast
Pus draining from the nipple
You will be asked about your symptoms and health history. A physical exam will be done. If the diagnosis is uncertain, or if mastitis recurs, your doctor may do:
Culture of breast milk or nipple discharge—to look for bacteria
—if a pocket of pus is suspected
Other conditions may cause similar symptoms. Your doctor may want to do tests to rule these out. Options may include:
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