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 one breast it can occur in both.


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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

Factors that may increase your chance of mastitis include:

  • 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
  • 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

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

Your doctor will ask 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 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 though, to make sure the medications are not harmful to your baby.
  • Offering the baby the inflamed breast first to promote complete emptying of 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 his or her chin points towards the blockage to promote emptying of the blockage
Pain Relief

To 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.

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.


To help reduce your chance 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 recommended by your doctor