Breast infection and inflammation

Is my breast infected?

Mastitis usually refers to a bacterial infection of the breast. The breast will be red, warm, tender, painful, and swollen. Mothers may feel unwell or have a fever. It is common in breastfeeding mothers. Mastitis can lead to the formation of an abscess, a collection of pus in the breast. Other conditions such as breast cancer, engorgement, and plugged ducts can look like mastitis.

A) Breast infections

When breastfeeding, a mother may notice her breast becoming red, tender, painful, and swollen. Most commonly, this is mastitis and is caused by a bacterial infection of the breast. Mothers can also have fevers and feel very sick.

Mastitis requires effective treatment. Mothers with mastitis are strongly encouraged to continue breastfeeding to speed healing and to prevent the formation of an abscess, a collection of pus inside the breast. There are a number of ways to keep mastitis from coming back. 

Similarly, abscesses require effective treatment and if possible, mothers are encouraged to continue breastfeeding.  

Mastitis and abscesses can develop in newborn babies and in pregnant women (Brett 2012; Efrat 1995; Malik 2015). Women who develop mastitis but are not breastfeeding are at a higher risk of having underlying breast cancer (Chang 2019; Chen 2020). 

Breastfeeding mothers can develop a lactational phlegmon, which is a localized area consisting of inflammation, infection, and pockets of fluid. It has characteristics of both mastitis and an abscess. This may need treatment with surgery, antibiotics, or a drain (Johnson 2019).

Another condition that is thought to be associated with bacteria is called subacute mastitis. It may cause ongoing breast pain without other changes and may be caused by an imbalance of bacteria in the milk ducts. Research on this condition is very limited.

B) Other causes of painful, red breasts

There are other problems that can result in the breast being red, warm, tender, and painful. These changes are the result of inflammation, the body’s response to a challenge.

Breast engorgement can mimic mastitis but generally affects both breasts, whereas mastitis is more likely in only one breast. 

A certain type of breast cancer (inflammatory breast cancer) can mimic mastitis. Breast cancer can also block milk drainage from the breast and cause mastitis. Mothers whose mastitis does not clear or returns in the same area should be tested for this. 

Plugged ducts and other causes of breast lumps cause inflammation.

Less common causes of breast inflammation are (Boakes 2018):

  • Diabetes (Makanjuola 2013)
  • Products such as silicone that have been introduced
  • Diseases caused by the body attacking itself, including sarcoidosis and lupus (Altintoprak 2013; Voizard 2017)
  • Granulomatous mastitis
  • The death of parts of the breast (comedo mastitis)
  • Abscesses under the areola (Zuska-Atkins disease)

If you are being treated for mastitis or an abscess and the condition does not respond quickly, ask your health-care providers to investigate further.


Altintoprak F, Karakece E, Kivilcim T, et al. Idiopathic granulomatous mastitis: an autoimmune disease? The Scientific World Journal. 2013;2013:148727
Boakes E, Woods A, Johnson N, et al. Breast Infection: A Review of Diagnosis and Management Practices.. Eur J Breast Health 2018; 14: 136-143
Brett A, Gonçalves S, Luz A, et al. [Neonatal mastitis: 12 years of experience]. [Article in Portuguese] Acta Med Port. 2012 Jul-Aug;25(4):207-12
Chang CM, Lin MC, Yin WY. Risk of breast cancer in women with non-lactational mastitis. Sci Rep. 2019 Oct 30;9(1):15587

Chen YC, Chan CH, Lim YB, et al. Risk of Breast Cancer in Women with Mastitis: A Retrospective Population-Based Cohort Study. Medicina (Kaunas). 2020 Jul 24;56(8):E372
Efrat M, Mogilner JG, Iujtman M, et al. Neonatal mastitis--diagnosis and treatment. Isr J Med Sci. 1995 Sep;31(9):558-60
Johnson HM, Mitchell KB. Lactational phlegmon: A distinct clinical entity affecting breastfeeding women within the mastitis-abscess spectrum. Breast J. 2019 Sep 8
Makanjuola D, Al Kushi A, Al Zaid M. Breast inflammation in type 1 diabetes. West Afr J Med. 2013 Apr-Jun;32(2):99-105
Malik S, Patil VA, Korday CS, et al. Antepartum Mastitis: A Rare Occurrence. J Hum Lact. 2015 Aug;31(3):367-70

Voizard B, Lalonde L, Sanchez LM, et al. Lupus mastitis as a first manifestation of systemic disease: About two cases with a review of the literature. Eur J Radiol. 2017 Jul;92:124-131