Part 1 of 6

What Is a Breast Infection?

A breast infection, also known as mastitis, is an infection that occurs within the tissue of the breast. Breast infections are most common among women who are breastfeeding, when the nipples become cracked and sore, allowing bacteria from a baby’s mouth to enter the breast. This is also known as lactation mastitis. Mastitis also occurs in women who aren’t breastfeeding, but this is not as common.

Infection typically affects the fatty tissue in the breast, causing swelling, lumps, and pain. Although most infections are due to breastfeeding or clogged milk ducts, a small percentage of breast infections are associated with rare kinds of breast cancer.

Part 2 of 6

What Causes Breast Infections?

The cause of most breast infections is Staphylococcus aureus bacteria, which cause what is commonly known as a staph infection. Streptococcus agalactiae is the second most common cause.

For breastfeeding mothers, a plugged milk duct can cause milk to back up and an infection to begin. Breastfeeding can cause cracked nipples and milk duct openings. If this happens, bacteria from the baby’s mouth can enter and cause an infection. The bacteria that typically cause infection are normally found on the skin, even when no infection is taking place. If the bacteria get into the breast tissue, they can multiply very fast and cause painful symptoms.

You can continue to breastfeed even when you have a mastitis infection because the bacteria are not harmful to your baby. This condition usually occurs in the first few weeks of breastfeeding, but it can occur later.

Non-lactational mastitis occurs in women with weakened immune systems, including women who have had lumpectomies with radiation therapy and women with diabetes. Some infection-like symptoms are a sign of inflammatory breast cancer, but this is very rare.

Subareolar abscesses occur when the glands under the nipple become blocked and an infection develops under the skin. This can form a hard, pus-filled lump that may need to be drained. This type of abscess normally only occurs in non-lactating women, and there are no known risk factors for it.

Part 3 of 6

What Are the Symptoms of Breast Infection?

Symptoms of a breast infection can start suddenly and may include:

  • abnormal swelling, leading to one breast becoming larger than the other
  • breast tenderness
  • pain or burning while breastfeeding
  • a painful lump in the breast
  • itching
  • warm breast
  • chills
  • nipple discharge that contains pus
  • skin redness in a wedge-shaped pattern
  • enlarged lymph nodes in the armpits or neck region
  • fever over 101ºF, or 38.3 ºC
  • feeling ill or rundown

You may experience flu-like symptoms prior to noticing any changes in your breasts. Contact your doctor if you have any combination of these symptoms.

Inflammatory Breast Cancer

Symptoms of a breast infection may also be associated with inflammatory breast cancer, which is a rare but serious disease. This type of cancer begins when abnormal cells in the breast ducts divide and multiply quickly. These abnormal cells then clog the lymphatic vessels (part of the lymphatic system, which helps remove waste and toxins from the body) in the skin of the breast, causing red, swollen skin that is warm and painful to the touch. Breast changes may occur over the course of several weeks.

Symptoms of inflammatory breast cancer may include:

  • thickness or visible enlargement of one breast
  • unusual warmth in the affected breast
  • discoloration of the breast, making it appear bruised, purple, or red
  • tenderness and pain
  • dimpling of the skin, similar to orange peel
  • enlarged lymph nodes under the arm or near the collarbone

Unlike other forms of breast cancer, women with inflammatory breast cancer do not develop lumps in the breast. This condition is often confused with a breast infection. Contact your doctor if you experience any of these symptoms.

Part 4 of 6

How Is a Breast Infection Diagnosed?

In a breastfeeding woman, a doctor can typically diagnose mastitis based on a physical examination and a review of your symptoms. Your doctor will also want to rule out whether the infection has formed an abscess that needs to be drained, which can be done during the physical exam.

If the infection keeps coming back, breast milk may be sent to a laboratory to determine what bacteria might be present.

Other tests may be necessary to determine the cause if you have a breast infection and you are not breastfeeding. Testing may include a mammogram or even a biopsy of breast tissue to rule out breast cancer. A mammogram is an imaging test that uses low energy X-rays to examine the breast. A breast biopsy involves the removal of a small tissue sample from the breast for lab testing to determine if any cancerous cell changes are present.

Part 5 of 6

What Treatments Are Available for Breast Infections?

A 10- to 14-day course of antibiotics is generally the most effective form of treatment for this type of infection, and most women feel relief within 48 to 72 hours. It’s important to take all medication as prescribed to make sure the infection doesn’t happen again. You can continue to breastfeed while on most antibiotics, but if nursing is uncomfortable, you can use a breast pump to relieve engorgement and prevent a loss of milk supply.

If you have an abscess due to a severe infection, it may need to be lanced (clinical incision) and drained. You may have to stop breastfeeding temporarily if you have an abscess.

If your doctor determines that inflammatory breast cancer is causing your symptoms, they will begin treatment based on the stage (severity) of your cancer. Treatment typically involves chemotherapy (using chemicals intravenously to kill cancer cells), radiation therapy (using high-powered X-rays to kill cancer cells), or surgery to remove the breast and surrounding lymph nodes.


While receiving treatment for infection, you can also take steps to relieve uncomfortable symptoms at home:

  • Warm compresses may ease pain and help lactation. Try applying a warm, wet washcloth to the infected area for 15 minutes, four times a day.
  • Anti-inflammatory medications, such as ibuprofen, may help relieve pain.
  • Use varied positions to breastfeed.
  • If possible, avoid prolonged engorgement before breastfeeding.

Meeting with a lactation consultant to alter your breastfeeding technique or position may help prevent the infection from returning.

Part 6 of 6

What Is the Long-Term Outlook for Breast Infection?

Antibiotics are very effective in treating an infection. You’ll probably feel better within two days, but it’s important to finish the entire course of antibiotics.

With diligent self-care and adherence to your doctor’s directions, you can reduce your risk of a recurrence.