What is mastitis (breast inflammation)?

Dr. Stuart A. Linder, MD
Plastic Surgeon

Mastitis is a breast infection involving the breast tissue. Symptoms include severe pain, breast mass, swelling and enlargement, fever, redness and possible nipple discharge. The causes include bacterial infection through a crack in the skin from Staphylococcus aureus. These bacteria may enter through the nipple or the surrounding skin breakage. The infection may spread deep into the tissue causing severe pain, swelling and a fever. It is most common in pregnant women that are breast feeding.

An abscess is the most common complication of untreated mastitis leading to deep tissue collection of pus. Treatment early on should be aggressive with moist warm compression and oral antibiotics. An abscess may require surgical drainage and intravenous antibiotics.

Cellulitis of the skin, mastitis of the breast and painful nipple discharge should be evaluated by a healthcare professional immediately.

There are two broad categories of mastitis, non-infectious mastitis and infectious mastitis. Non-infectious mastitis results from breast milk staying within the breast tissue (milk stasis), usually because of a problem with breastfeeding the baby. The patient may notice a hard, sore spot inside the breast. Mastitis can occur as a result of an infection or a blocked milk duct. If untreated, the milk that remains stagnant in the breast tissue can become infected, which may lead to infectious mastitis. Infectious mastitis is caused by a bacterial infection of mammary gland breast tissue and the consequent inflammation.

The diagnosis of mastitis is made clinically based on a physical exam, unilateral localized breast tenderness and erythema, accompanied by a fever, malaise, fatigue, body aches, headache and/or a wedge-shaped area tender to the touch on the breast that points toward the nipple. As part of the physical examination, the physician will rule out other concerning conditions that can cause redness and swelling that could be confused with mastitis.

Because signs and symptoms can develop rapidly, it is important to receive treatment immediately to prevent further complications of the breast. These conditions could include a breast abscess or a rare form of breast cancer called inflammatory breast cancer. Your doctor may recommend a diagnostic mammogram, and you may need a biopsy to make sure you don't have breast cancer.

Although mastitis usually occurs in the first several weeks postpartum, it can happen anytime during breastfeeding and as many as two years after cessation of breastfeeding. In rare cases, mastitis can affect women who are not lactating or breast feeding. Some mothers mistakenly wean their babies before they intend to when they develop mastitis. In most cases breastfeeding can continue during mastitis.

Mastitis affects approximately 10 percent of all mothers producing breast milk and breastfeeding their babies. However results have varied significantly. Some studies indicate that only 3 percent of women develop mastitis, while others say 33 percent.

A clogged milk duct is generally not a problem, but left untreated it can develop into a more serious infection called mastitis, which usually requires antibiotics. You'll know you've developed mastitis if you have a fever and feel like you have the flu. Usually, there's also a tender, red, wedge-shaped area on the surface of the breast. Left untreated, mastitis can develop into a breast abscess, which may require significant medical treatment, including surgery.

Mastitis is a swelling and infection of the breast tissue and glands—not an infection of your milk. Most breast infections result from missed feedings or not frequently emptying your breasts, leading to milk buildup. You are also more likely to develop a breast infection if you have damaged nipples or plugged ducts—or if your defenses are lowered by lack of rest, poor diet or stress.

Symptoms of a breast infection (mastitis) may include flu-like symptoms (such as chills, body aches, fatigue, headache and fever above 100.4°F) and a throbbing pain in one breast. In addition, an area of your breast may be red and painful to the touch, or the skin may look tight and shiny.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.