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Mastitis is an infection of the ducts of the breast. It usually only occurs in women who are breastfeeding their babies.


In the process of breastfeeding, the unaccustomed pull and tug by the infant suckling at the breast may

result in the mother's nipples may becoming sore, cracked, or slightly abraded. This creates a tiny opening in the breast, through which bacteria can enter. The presence of milk, with high sugar content, gives the bacteria an excellent source of nutrition . Under these conditions, the bacteria are able to multiply, until they are plentiful enough to cause an infection within the breast.

Mastitis is most likely to occur in the fifth and sixth week of the postpartum period. Studies indicate an incidence of mastitis from 6–33% of all women who have a history of breastfeeding.

Causes and symptoms

The most common bacteria causing mastitis is Staphylococcus aureus, but sometimes Escherichia coli is responsible. In rare instances, Streptococcus can also induce an episode of mastitis. In 25–30% of people, Staphylococcus aureus is present on the skin, lining normal, uninfected nostrils. It is probably this bacteria, clinging to the baby's nostrils, that is available to create infection when an opportunity (i.e., a crack in the nipple) presents itself. A sluggish flow of milk and trauma to the nipples are the main contributing factors to the development of mastitis. Fatigue, stress , and returning to work may also predispose a nursing mother to developing the condition.


The clinic, midwife, or office of the physician will most likely receive a call from the mother at home. The condition rarely occurs in the hospital. She will likely report general malaise, fatigue, headache, chills, an increased heart rate, and flu-like symptoms. Usually, only one breast is involved. An area of the affected breast becomes swollen, red, hard, and painful. A red streak may be evident. Often, the location of the infection is in the upper, outer quadrant, which is the location of most of the glandular tissue.

Lumps in the breasts may result from plugged milk ducts. Plugged ducts can contribute to mastitis. If the mother describes pain in both breasts, then the condition might be engorgement of the breasts, as opposed to mastitis, which almost always occurs unilaterally.

A definitive diagnosis of the offending pathogen involves obtaining a sample of breast milk from the infected breast. A culture is done to identify the pathogen. In practice, however, laboratory studies are done infrequently because antibiotic therapy is initiated before results are returned, and insurance companies may not cover the cost of the tests.


A penicillinase-resistant penicillin or a cephalosporin, for six to 10 days, can both be used to treat mastitis. Low doses of erythromycin or trimethoprin-sulfamethoxazole over an extended period of time have been used to treat chronic mastitis. Breastfeeding should be continued, because the rate of abscess formation in the infected breast increases sharply among women who stop breastfeeding during a bout of mastitis. Some symptoms of mastitis respond solely to frequent breastfeeding and pumping, without requiring antibiotic therapy. Most practitioners allow women to take acetaminophen while nursing, to relieve both fever and pain. Since almost all drugs the mother takes appear in her breast milk, any medication taken by breastfeeding women must also be safe for the baby. Warm, moist compresses applied to the affected breast can be soothing. Increasing fluid intake and bed rest are also recommended.


Prognosis for uncomplicated mastitis is excellent. A small percentage of women with mastitis will end up with an abscess within the affected breast. This complication will require a surgical procedure to drain the pus. In the case of a small abscess, aspiration with a needle under the direction of ultrasound may be the preferred method of treatment. A larger abscess requires an incision be made into the affected area, so that drainage can occur. A drain in the wound may be placed to facilitate further drainage. Manual expression of the site allows for elimination of pus and milk. The wound normally heals in one to two weeks.


Abscess —A persistent pocket of pus.

Lactation consultant —A health care provider who is certified in managing the breastfeeding concerns of mothers.

Health care team roles

The registered nurse (R.N.) and lactation consultant are frequently the first to speak with the mother who has mastitis. Rapid diagnosis, followed by treatment, can prevent the formation of an abscess. It is imperative to help the mother understand that continuation of breastfeeding is part of successful management of mastitis. It should be emphasized to her that abrupt cessation will actually worsen the problem.

Patient education

When counseling a mother who has mastitis, the health care provider should encourage her to breastfeed frequently and to use a breast pump if the baby does not adequately empty the breast. The mother should be instructed to start each nursing session by breastfeeding her baby on the breast that is not affected, because the baby's initial sucks will be the most vigorous ones. Once the baby switches to the affected breast, the milk will have already started to flow in "letdown reflex," and the baby's sucking will be less painful. The health care provider should instruct the mother to rest, increase her fluid intake, and take medications as prescribed.


To prevent mastitis, mothers should breastfeed frequently, ensuring adequate emptying of each breast at least every other nursing session. Handwashing is important in decreasing the chance of spreading bacteria to the breasts. Mothers should also be instructed to avoid wearing tight bras, skipping feedings, and becoming overly tired.



Biancuzzo, Marie. Breastfeeding the Newborn. Herndon, VA: Mosby, 1999.

Cunningham, F. Gary, et al., eds. Williams Obstetrics. Stamford, CT: Appleton & Lange, 1997.

Riordan, Jan, and Kathleen Auerbach. Breastfeeding and Human Lactation. Boston, MA: Jones and Bartlett, 1999.


LaLeche League International. 1400 N. Meacham Rd., Schaumburg, IL 60173-4048. (847) 519-7730 or (800) LALECHE. <>.

Nadine M. Jacobson