Breast Infection

Written by Christine Case-Lo | Published on September 10, 2012
Medically Reviewed by Brenda B. Spriggs, MD, MPH, FACP

What Is a Breast Infection?

A breast infection, also known as mastitis, is an infection that occurs in 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 known as lactation mastitis. Mastitis also occurs in women who are not breastfeeding, but this is rare.

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

What Causes Breast Infections?

Most breast infections are caused by Staphylococcus aureus bacteria.

For breastfeeding mothers, a plugged milk duct can cause milk to “back up” and an infection to begin. Breastfeeding may also cause cracked nipples or milk duct openings, where bacteria from the baby’s mouth can enter and cause an infection. The bacteria that typically cause infection can normally be found on the skin, even when no infection is taking place. However, if they get inside 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 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 normally only occurs in non-lactating women, however, there are no known risk factors for this condition.

What Are the Symptoms of Breast Infection?

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

  • one breast that is larger than the other due to abnormal swelling
  • breast tenderness
  • pain or burning while breastfeeding
  • a painful lump in the breast
  • itching
  • nipple discharge that contains pus
  • skin redness in a wedge-shaped pattern
  • enlarged lymph nodes in the armpits
  • fever over 101 degrees Fahrenheit, or 38.3 degrees Celsius
  • 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 a rare but serious condition called inflammatory breast cancer. This type of cancer begins when abnormal cells in the breast ducts divide and multiply at a rapid rate. These abnormal cells then clog 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 in color
  • tenderness and pain
  • dimpling of the skin, similar to an 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. As such, this condition is often confused with a breast infection. Contact your doctor if you experience any of these symptoms.

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 nipples may be sent to a laboratory to determine what bacteria might be present.

If you have a breast infection and you are not breastfeeding, other testing may be necessary to determine the cause. 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 testing in a laboratory to determine if any cancerous cell changes are present.

What Treatments Are Available for Breast Infections?

A 10-14 day course of antibiotics is often the most effective form of treatment for this type of infection, and most women will feel relief within 48 hours. However, it is important to finish all medication as prescribed to make sure the infection does not recur. You can continue to breastfeed while on most antibiotics, but if nursing is uncomfortable, you can relieve engorgement and prevent loss of milk supply with a breast pump.

If you have an abscess due to a severe infection, it may need to be lanced (clinical incision) and drained. You may have to temporarily stop breastfeeding 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 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 breast feed
  • If possible, avoid prolonged engorgement before breastfeeding

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

What Is the Long-Term Outlook for Breast Infection?

Antibiotics are very effective in treating infection. Within two days, you will probably feel better, but it is important to finish the entire course of antibiotics.

What Are the Complications of Breast Infections?

A severe infection can cause an abscess, which may need to be surgically drained. Abscesses can leave scars or deform tissue. You may also have to stop breastfeeding temporarily in order for the abscess to heal.

Inflammatory breast cancer can mimic the symptoms of a breast infection. If you appear to have this type of infection and are not breastfeeding, talk to your doctor about screening for this type of cancer.

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