What Is Mastitis? - Causes, Symptoms & Treatment

Instructor: Sarah Lawson

Sarah has taught nursing courses and has a master's degree in nursing education.

Mastitis is a very painful condition that mainly affects breastfeeding mothers, usually in the first few months of breastfeeding. Learn more about the causes, symptoms, and treatment of mastitis and test your knowledge with a quiz.

What is Mastitis?

Breastfeeding is a wonderful experience for many mothers. It is a time of bonding, cuddling, and building the mother-infant relationship. However, this isn't the case for all women. For some, breastfeeding is not wonderful; it is difficult and even painful. It can be excruciating to latch a baby on to sore and cracked nipples. Some women who are having difficulty with nursing choose to skip feedings because she knows it will be painful. Doing so can lead to mastitis.

Mastitis is inflammation of the breast tissue usually caused by infection. It causes pain, swelling, redness, and warmth of the affected breast. It most commonly occurs to women who are breastfeeding, or directly feeding an infant breast milk from the breast. It is possible to get mastitis while not breastfeeding, though far less common. It can result from tissue injury or other infection. In very rare cases, men can develop mastitis.

Mastitis most often occurs during the first three months of breastfeeding. Women who have mastitis often feel very tired and run-down making it difficult to care for their baby. Breastfeeding and caring for a baby is already difficult, so when mastitis occurs, many women will wean their baby, even if it is sooner than they intended to.


Mastitis occurs when bacteria enters the breast tissue. 'Staphylococcus aureus', or 'S. aureus', is the most common bacterium to cause mastitis. This infection can happen from nursing when a mother has cracked and sore nipples. Milk stasis, skipping breast feeding sessions or going long periods of time in between feedings, increases the likeliness of mastitis. With skipped feedings, the breasts become engorged, or too full of milk, a condition leading to mastitis. Other causes of mastitis include tight-fitting clothing and poorly-fitting bras because they can compress breasts, preventing the circulation necessary to keep breast tissue healthy.

Serous exudate from mastitis in milk on left; Normal breast milk on right
Serous exudate from mastitis in milk on left; Normal breast milk on right

Mastitis and breast abscesses can be caused by direct injury to the breast tissue. Instances of mastitis in non-nursing mothers can occur following a traumatic event to the chest, sporting activities, or even a seat belt injury. It is also possible for mastitis to occur from surgery or cosmetic procedures. Possible causes include a contaminated breast implant or the introduction of a other foreign body to the breast tissue such as a piercing. In either case, the foreign body will need to be removed.


The following are symptoms that women experience with mastitis:

  • Increased pain, swelling, redness, and warmth usually in one area of the breast
  • Red streaks in the breast
  • Pus draining from a breast
  • Swollen lymph nodes in the neck or armpit
  • Flu-like symptoms including fever (101°F and higher), chills, aches, and fatigue


It is very important that breasts be emptied of milk when nursing; this is true when mastitis is present and when it is not. When mastitis is present, continued breastfeeding is recommended. Even during mastitis, the mother's breastmilk is fine for the baby to ingest. Massaging the breasts and using warm compresses prior to and during feedings helps to increase circulation and assist in emptying the breast of milk. It is recommended for the mother to drink plenty of fluids and to get adequate rest. For many women, this may be all the treatment that is necessary.

Breastfeeding on a regular schedule is the best way to prevent and treat mastitis
Breastfeeding on a regular schedule is the best way to prevent mastitis

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