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Health Information Center


  • Cynthia M. Johnson, MA
Publication Type:



(Breast Infection)


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 mastitis that occurs with breastfeeding.


Nucleus factsheet imagehttp://services.epnet.com/getimage.aspx?imageiid=73527352si55551247.jpgsi55551247.jpgNULLjpgsi55551247.jpgNULL\\hgfiler01a\intellect\images\si55551247.jpgNULL14NULL2008-11-07254390Copyright © Nucleus Medical Media, Inc.


Mastitis is caused by an oversupply of milk. This causes the milk ducts to narrow from the pressure surrounding them. Bacteria can then enter the breasts through the milk duct or cracks in the skin of the nipples. Once there, it can grow and cause an infection.

Risk Factors

Things that may raise the risk of mastitis are:

  • A history of mastitis
  • A buildup of milk in the breasts due to:
    • Blocked milk ducts
    • Lactating more breastmilk than is needed
    • Pressure on the breasts, such as from tight clothing and bras
    • Sudden changes in breastfeeding frequency
    • Weaning
  • Frequent breast pumping
  • Nipple damage, such as cracks, dryness, and sores
  • Wearing nipple shields


Mastitis may cause:

  • Redness, tenderness, or swelling of the breast
  • A burning feeling in the breast
  • Fever
  • Tiredness
  • Aches, chills, or other symptoms that are like the flu
  • A hard feeling or tender lump in the breast
  • Pus draining from the nipple


The doctor will ask about symptoms and past health. A physical exam will be done. It will focus on the breast. This is often enough to make the diagnosis.


The goal of treatment is to ease swelling and pain and to treat an infection if one is present. A woman can continue to breastfeed during treatment.

Options are:


To lower the risk of mastitis:

  • Use proper methods to breastfeed and express milk
  • Drink plenty of fluids and eat a healthful diet
  • Avoid tight clothing and bras
  • Avoid nipple shields

Supportive Care

General steps manage mild mastitis are:

  • Using proper methods to breastfeed and express milk
  • Taking over the counter pain medicine
  • Applying warm or cold compresses
  • Drinking plenty of fluids and eating a healthful diet




  • Lactational mastitis. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/lactational-mastitis.
  • Mastitis. Family Doctor—American Academy of Family Physicians website. Available at: https://familydoctor.org/condition/mastitis.
  • Nonlactational mastitis. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/nonlactational-mastitis.
  • Pediatric masitis. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/pediatric-mastitis.


  • Mark S. Itzkowitz, MD, JD
Last Updated:

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.