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(Breast Infection)


Mastitis is painful swelling and redness in the breast. It is especially common among women who are breastfeeding. While it is most common in just 1 breast at a time, it can occur in both breasts at the same time.


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Causes    TOP

Mastitis is often caused by trapped breast milk 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 a bacterial infection in the breast tissue. Milk ducts or cracked skin around the nipple can allow bacteria to enter the breast and cause an infection.

Mastitis often occurs during breastfeeding but, it is possible to get mastitis at other times. This fact sheet will focus on symptoms and treatment of lactation-associated mastitis.

Risk Factors    TOP

Factors that may increase your chances of mastitis:

  • Previous 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:
    • Irregular breastfeeding
    • Missed breastfeeding, which may cause overdistention of the breast
    • Baby's teething
    • Use of supplemental bottle feeds
    • Incorrect positioning of the baby during feedings
    • Abrupt weaning

Symptoms    TOP

Mastitis may cause:

  • Redness, tenderness, or swelling of the breast
  • Fever
  • Fatigue
  • 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

Diagnosis    TOP

You will be asked about your symptoms and medical history. A physical exam will be done. If the diagnosis is uncertain, or if mastitis recurs, your doctor may do a:

  • Culture of breast milk or nipple discharge
  • Breast ultrasound if an abscess is suspected

In some cases, your doctor may want to look for other conditions that may cause similar symptoms. In these situations, other tests may be performed such as a:

Treatment    TOP

Treatment may include:

Methods to Clear Blocked Breast Ducts

Relieving the blockage in the milk duct is an effective way to decrease the pain and swelling. To clear blocked breast ducts try:

  • Breastfeeding frequently—Breastfeeding with mastitis is not harmful to the baby. Talk to your doctor if you are also taking medications to make sure they are not harmful to your baby.
  • Offering the baby the inflamed breast first to promote complete emptying of the infected breast
  • Using a breast pump to express milk
  • Applying warm compresses to breasts or taking a warm shower prior to feeding to stimulate milk ejection reflex
  • Massaging the inflamed breast before feeding
  • Positioning your infant so their chin points towards the blockage to promote emptying of the blockage

Pain Relief

To help reduce pain and swelling in the breast:

  • Apply ice compresses to the affected area of your breast after breastfeeding.
  • Consider using over-the-counter pain relievers as recommended by your doctor.
  • Be sure to ask your doctor what pain relievers are safe for you and your baby. Taking aspirin is not advised during pregnancy or breastfeeding.
  • Drink lots of fluids.
  • Get plenty of rest.

Medication    TOP

Antibiotics may be used to treat the infection. They may help cure the infection or reduce the risk of more serious but rare complications such as blood infection. If you are breastfeeding, talk to your doctor about which antibiotics are best for you to take so you can continue to breastfeed.

If mastitis does not respond to antibiotics, a localized collection of pus called an abscess might be present. This is usually treated with other antibiotics and a drainage procedure or surgery.

Prevention    TOP

To help reduce your chances of mastitis:

  • Breastfeed frequently.
  • Use a breast pump when you need to.
  • Wash your hands and breast nipple before breastfeeding.
  • Avoid wearing bras or clothing that is too tight.
  • Avoid sleeping on your breasts, or allowing a baby to sleep on your breasts.
  • If your nipples crack, apply lotion or cream as advised by your doctor.


Office on Women's Health
The American Congress of Obstetricians and Gynecologists


Canadian Women's Health Network
Society of Obstetricians and Gynaecologists of Canada


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Laibl VR, Sheffield JS, Roberts S, McIntire DD, Trevino S, Wendel GD Jr. Clinical presentation of community-acquired methicillin-resistant Staphylococcus aureus in pregnancy. Obstet Gynecol. 2005;106(3):461-465.
Mastitis. Family Doctor—American Academy of Family Physicians website. Available at: Updated April 1, 2014. Accessed April 17, 2018.
Masitis. EBSCO DynaMed website. Available at: Updated March 15, 2016. Accessed April 17, 2018.
Spencer J. Management of mastitis in breastfeeding women. Am Fam Physician. 2008;78(6):727-731.
11/5/2014 DynaMed's Systematic Literature Surveillance Amir L, The Academy of Breastfeeding Medicine Protocol Committee. ABM clinical protocol #4: mastitis, revised March 2014. Breastfeed Med. 2014;9(5):239-243.
Last reviewed March 2018 by EBSCO Medical Review Board Marcie L. Sidman, MD
Last Updated: 11/5/2014

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