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(Breast Infection)

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Mastitis is inflammation of the breast and is seen almost exclusively in women. It is especially common among women who are breastfeeding. Mastitis usually affects only one breast, but may affect both breasts.


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Mastitis occurs when a milk duct in the breast becomes blocked, or the skin around the breast nipple becomes cracked. Both of these situations allow bacteria to enter and infect the breast tissue. Causes of mastitis include pregnancy, breastfeeding, tuberculosis , skin rashes, or, rarely, breast cancer . This article will focus on symptoms and treatment of lactation-associated mastitis.

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.

Risk factors include:

  • Previous mastitis
  • Abrasion or cracking of the breast nipple
  • Wearing a bra or clothing that is too tight
  • Missed breastfeeding
  • Irregular breastfeeding
  • Pressure on the breasts, caused by:
    • 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:
    • Baby's teething
    • Use of artificial nipple or pacifier
    • Incorrect positioning of the baby during feedings
    • Abrupt weaning
  • Yeast infection of the breast
  • Low resistance to infection or immune deficiency disorder
  • Psoriasis or other skin conditions that affect the nipple
  • Diabetes mellitus
  • Rheumatoid arthritis
  • Use of cortisone drugs
  • Prior breast surgery or implants
  • Smoking


Symptoms may include:

  • Fever
  • Fatigue
  • Nausea or vomiting
  • Aches, chills, or other flu-like symptoms
  • Redness, tenderness, or swelling of the breast
  • A burning feeling in the breast
  • A hard feeling or tender lump in the breast
  • Pus draining from the nipple
  • Swollen lymph glands in the armpit or above the collar bones


Your doctor will ask about your symptoms and medical history, and examine your breast. If the diagnosis is uncertain, or if mastitis recurs, your doctor may order the following tests:


Treatment may include:


Antibiotics are generally used to treat the infection and there is evidence that they may reduce the duration of symptoms. Whether antibiotics are necessary for a cure or to reduce the risk of more serious, but rare complications, such as bloodstream infection, is unknown.

If mastitis does not respond to antibiotics, a localized collection of pus called an abscess might be present. This is usually treated with antibiotics and a drainage procedure or surgery. The bacteria known as Staphylococcus aureus is responsible for many cases of bacterial mastitis and most abscesses, but in recent years “staph” has become resistant to many of the commonly used antibiotics. Resistant bacteria have so far only rarely been reported in association with mastitis, but it seems likely that antibiotic resistance will eventually be seen in mastitis, probably requiring a change in the usual antibiotics chosen for this infection.

Methods to Clear Blocked Breast Ducts

Methods to clear blocked breast ducts include:

  • Breastfeeding frequently—Breastfeeding with mastitis is not harmful to the baby when treatment involves antibiotics such as cephalexin, amoxicillin, or erythromycin. The use of some other antibiotics may dictate caution, especially when breastfeeding an infant under eight weeks of age. Ask your doctor’s advice if antibiotics such as bactrim (trimethoprim-sulfamethoxazole) or doxycycline are used.
  • Using a breast pump
  • Applying warm compresses to breasts prior to feeding (to stimulate milk ejection reflex)
  • Offering the baby the infected breast first (to promote complete emptying of infected breast)

Pain Relief

To reduce pain and swelling in the breast:

  • Apply ice compresses to the affected area of your breast after breastfeeding.
  • If your mastitis is not caused by breastfeeding, consider using over-the-counter pain relievers as recommended by your doctor.
  • If your mastitis is caused by pregnancy or breastfeeding, 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.


Strategies to help prevent mastitis include:

  • Prevent engorgement of the breast with milk by:
    • Frequent breastfeeding
    • Use of breast pump
  • 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.


The American Medical Association Women's Association

National Women's Health Information Center


BC Health Guide

Women's Health Matters


American Academy of Pediatrics website. Available at: .

Amir L. Breastfeeding and Staphylococcus aureus : three case reports. Breastfeed Rev . 2002;10:15-18.

Barbosa-Cesnik C, Schwartz K, Foxman B. Lactation mastitis. JAMA . 2003;289:1609-1612.

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;106:461-465.

Medline Plus website. Available at .

The Merck Manual of Medical Information . 17th ed. Simon and Schuster, Inc; 2000.

Last reviewed November 2007 by Jeff Andrews, MD, FRCSC, FACOG

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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