The Facts

Mastitis, also known as breast infection, is an infection of the breast tissue. It is caused by bacteria that usually enter the breast through small cracks in the nipple, then multiply within the fatty tissue of the breast.


Mastitis can occur when bacteria commonly found on the skin enter the nipple through small cracks. The bacteria then multiply in the fatty tissue of the breast surrounding the milk ducts (areas of the breast that produce milk), causing swelling, warmth, or pain. The swelling can press on the milk ducts and block them.

Mastitis occurs most commonly in women who are breast-feeding. However, it may occur in women who are not breast-feeding as well. Staphylococcus aureus is the bacterium that is most often associated with this type of infection.

The infection can also occur after milk plugs one of the many milk ducts within the breast, trapping bacteria within the tissue. In this way, a blocked milk duct may also result in a breast infection.

Symptoms and Complications

Women who have mastitis may experience breast pain and may have a fever and feeling of being unwell. The pain is caused by swelling in the breast tissue. Other symptoms include:

  • breast tenderness, redness, enlargement, or sensitivity
  • warm area in breast tissue
  • itchiness
  • liquid or pus discharge from nipple
  • changes in sensation of the breast
  • fever
  • swollen lymph node on same side as affected breast
  • lump in breast

Severe infections may lead to pus-filled cysts called abscesses within the breast tissue. Such cases may require a woman to temporarily stop breast-feeding and may sometimes even require surgery.

Making the Diagnosis

To determine if you have mastitis, your doctor will perform a physical examination and ask you about your symptoms. No tests are usually required for breast-feeding women.

However, if you are not breast-feeding, your doctor may request certain tests to better understand your condition. These may include mammography or a biopsy (a tissue sample).

Treatment and Prevention

Women who are breast-feeding and have mastitis should:

  • get plenty of rest
  • apply a warm, moist cloth to the affected area several times a day
  • breast-feed frequently and use different breast-feeding positions to help unplug the affected milk duct

Antibiotics may also be used to treat mastitis when symptoms continue for more than 24 hours despite rest, heat, and frequent nursing. If antibiotics are prescribed, completing the antibiotic treatment is crucial to preventing a recurrence of the infection. Always take the medication as prescribed by your doctor.

Mothers who are breast- feeding are typically encouraged to continue nursing their babies while receiving treatment for mastitis. Breast-feeding can help clear plugged ducts, which will reduce the accumulation of milk and help the infant maintain proper nursing techniques. In general, mothers do not have to worry about harming the health of their baby as the antibiotics used to treat these infections are usually safe for breast-feeding.

Many mothers with mastitis worry about passing the infection to their infant. It is important to understand that breast milk contains many antibacterial components that protect the infant from infection.

Preventing future breast infections is possible. Try wearing well-fitted bras, breast-feed your infant frequently to keep milk ducts from plugging, avoid carrying heavy items over your shoulders (e.g., a purse, diaper bags, etc.), and use several different positions while breast-feeding to help drain different areas of the breast.