1. What every clinician should know

Mastitis is an acute inflammation of the connective tissue of the mammary gland; a mammary cellulitis. Mastitis is most commonly associated with breastfeeding, but can occur rarely during pregnancy and outside of pregnancy. The incidence of lactation mastitis is dependent on the population sampled. The American Congress of Obstetricians and Gynecologists (ACOG) and the World Health Organization (WHO) estimate incidence at 10-30%.

Mastitis occurs most commonly within the first 2-3 weeks postpartum, but may occur at any time during lactation. Mastitis is most commonly caused by skin organisms, with an increase in reports of methicillin-resistant Staphylococcus aureus (MRSA)-related mastitis.

Benefits of breastfeeding (BF):

The benefits of breastfeeding are largely based on observational cohort studies controlling for confounders. The data is not yet definitive on many of the effects. It is important to remember that causality is implied. As better studies are defined, these associations may change.

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Benefits to mother:
  • Reduces risk of breast cancer (dose-response effect)

  • Reduces risk of ovarian cancer (dose-response effect)

  • Little or no evidence for protection from postpartum depression, fractures from osteoporosis long-term, or return to pre-pregnancy weight

Benefits to term infants:
  • Reduces risk of acute otitis media (BF >4 months)

  • Reduces risk of atopic dermatitis in families with a history (BF >3 months)

  • Reduces risk of nonspecific gastrointestinal infections

  • Reduces risk of hospitalization for lower respiratory tract infections (BF >4 months)

  • Reduces risk of asthma (BF >3 months)

  • Reduces risk of obesity in childhood and later life

  • Reduces risk for Type 2 insulin-dependent diabetes mellitus (IDDM)

  • Reduces risk for sudden infant death syndrome (SIDS)

  • Little or no evidence for effect on cognitive performance, or protection from cardiovascular disease, or Type 1 IDDM

Benefits to preterm infants:
  • Reduces risk for necrotizing enterocolitis

  • Little or no evidence for effect on cognitive performance

There is a major nationwide public health effort underway to increase the number of women who breastfeed, with several professional societies, and local, national, and international organizations offering recommendations and support. Healthy People 2020 (a U.S. government initiative) set a goal for 81% of mothers to initiate breastfeeding, with 46% and 25% continuance at 3 and 6 months, respectively. The American Academy of Pediatrics recommends that all women breastfeed for 1 year and exclusively for the first 6 months.

The UNICEF/WHO global criteria for the baby-friendly hospital provides certification for hospitals and ensures adequate resources to help women through these challenges. Consequently, as more women breastfeed, more mastitis will be seen.

Risk factors

Antepartum mastitis is exceedingly rare. The data come solely from case reports. Risk factors are very different antepartum than postpartum as lactation has not begun. Risk factors are focused on breaks in the skin barrier due to a variety of causes: IV drug use with skin popping, physical abuse, trauma, burns, dermatologic conditions (eczema), uncontrolled scratching from pruritic urticarial papules and plaques of pregnancy (PUPPS), or cholestasis and systemic diseases (tuberculosis, sarcoidosis). Lastly, inflammatory breast cancer should always be considered.

Several risk factors for postpartum mastitis have been reported in the literature. The most common risk factor is a history of mastitis with a prior child. Physical risk factors include cracked nipples, blocked duct, use of a manual pump, use of creams on nipples, inverted nipples, breast implants, and breast surgery. An overabundance of milk, such as mothers nursing multiple infants, trauma from a physical injury, and infant-feeding related factors, such as engorgement, poor attachment, ineffective suckling, infrequent feedings, infants with short frenulums or cleft lip and/or palate, and pacifier use are also risks.

Pathophysiology and microbiology

Mastitis is thought to develop from milk stasis and inflammation, leading to infection. Skin breakdown, clinically seen as cracked nipples, may or may not be present. Natural defenses include a normally a balance of cytokines within breast milk that createsa natural defense against infection within the breast tissue. These include secretory IgA, lactoferrin, lysozyme, C3, and leukocytes. IgA and C3 aid in phagocytosis of bacteria. Lactoferrin promotes adhesion of leukocytes to sites of inflammation within the breast ducts.

Stasis elicits an inflammatory response, with a consequent elevation in anti-inflammatory cytokines such as IL-8, and a change in milk composition that includes an increase in sodium and chloride and a decrease in potassium and lactose. Mastitis is most commonly caused by maternal skin and nasal flora. Therefore, Staphylococcus aureus and coagulase-negative staphylococci, followed by Group A and B hemolytic, and non-hemolytic streptococci are the most commonly found bacteria.

These are followed by Escherichia coli,Haemophilus influenzae, Klebsiella, and Bacteroides.Candidal infections have also been reported, especially after antibiotic treatment, in mothers with poorly controlled diabetes and in immunocompromised women. Tuberculosis infections and other fungal infections are exceedingly rare. Methicillin-resistant S. aureus (MRSA) is increasingly reported and is a common cause of failed antibiotic therapy. The role of mother/infant skin and nasal bacterial colonization in the development of mastitis is poorly understood.

The CASTLE (Candida and Staphylococcus Transmission: Longitudinal Evaluation) study was recently completed in Australia. This study aimed to better characterize the role of nasal, skin (nipple), and vaginal bacterial colonization in the development of mastitis. This study recruited primiparous mom/baby couplets at delivery and collected bacterial swabs from the pair at that time and out to 6 weeks postpartum. With the rise of community-acquired MRSA, this is an issue of increasing clinical relevance.

2. Diagnosis and differential diagnosis


Mastitis is a clinical diagnosis. Women typically present with the following triad: fever (>38.5° C), pain (typically unilateral), and erythema (often wedge-shaped over area of infection). Most women have generalized flu-like symptoms. Bilateral mastitis has a reported incidence between 3% and 12%. The infection may be superficial (dermis) or intramammary, with parenchymal (glandular) and/or interstitial (connective tissue) involvement. An abscess complicates about 10% of mastitis cases. This is seen as a firm, very tender, often fluctuant mass in the area or erythema and pain. Ultrasound is the primary modality for imaging and should be done when there is concern about an abscess.

Differential diagnosis

Breast “fullness” or “let-down”: Occurs between the third and sixth postpartum day. This may be accompanied by a low-grade fever. However, this is physiologic and characterized by a normal flow of milk.

Breast engorgement: Breast(s) are overfilled such that there is obstruction to venous and lymphatic flow, and subsequently decreased milk flow. Breasts will appear diffusely swollen, shiny, and red, with flattening of the nipple. Most women note exquisite tenderness.

Blocked duct: This will present as an area of focal engorgement, palpated as a lump, with redness overlying. This can also present as a small white area (1 mm) on the nipple. This is from an overgrowth of skin at the duct end. Typically, women with a blocked duct feel well and do not have generalized flu-like symptoms. Women may often note particulate matter within their breast milk, which is from casein and salts.

Galactocele represents a milk-filled cyst. Women will present with a breast mass and no evidence of local or systemic infection. Galactoceles can recur, and often treatment requires removal of the cyst wall.

Fibroadenomas can also be confused with a breast mass. Typically, they do not become infected.

Breast cancer (inflammatory breast cancer) must be considered in atypical presentations or those not responding to initial therapy.

Breast thrush is very controversial, with little science to support thrush as an etiology. However, treatment for thrush is readily adopted by the lactation community. Breast thrush, or Candida infection of the ductal system, refers to the severe burning nipple and breast pain, not associated with redness and fever. Women often describe this pain as shooting to the chest wall, and it is out-of-proportion to physical examination findings. This occurs in roughly 10% of breastfeeding women.

Raynaud’s disease presents with isolated nipple pain during the let-down phase of breastfeeding.

3. Management

Management has three goals:

  • Proper antibiotic selection

  • Symptomatic relief

  • Continuation of breastfeeding


In uncomplicated mastitis, treatment should involve an antibiotic that is sensitive to the most common organisms and not degraded by beta-lactamase. Dicloxacillin or a first-generation cephalosporin (cephalexin) are first-line treatments. Macrolide antibiotics, such as erythromycin or clindamycin, should be used in cases of a penicillin allergy. Treatment should be continued for 10 to 14 days. Most women can be managed as an outpatient, but clinical judgment should prevail. Drugs with a broader range and typically more expensive choices such as Augmentin are not indicated as first-line therapy. Maternal symptoms should improve within 48 hours. If symptoms persist and clinical improvement is not seen, a different management scheme should be adopted.

Symptomatic relief

Relief of symptoms can usually be achieved with nonsteroidal anti-inflammatory drugs, rest, hydration, and warm compresses on the affected breast to aid in milk expression.There is limited data on complementary and homeopathic methods that are used in the lay lactation community. Cold cabbage leaves applied to the breasts have been used to help with the symptomatic relief of engorgement. Herbal plant extracts (chamomile), sulfur, or belladonna have also been reported. Use of Lactobacillus fermentum and Lactobacillus salivarius have been reported with success, but no formal recommendations exist. Use of such methods may be undertaken after discussion between patient, doctor, and lactation consultant.

Continuation of breastfeeding

This is important in the short term for the success of first-line treatment and important in the long term for the health of the infant. Emptying the breast is essential for successful treatment and to decrease complications of abscess formation. Teaching and supportive care encouraging continuation of breastfeeding is essential. Mastitis is the third leading reason for weaning, and one in four women cite it as the reason they stopped breastfeeding.

4. Complications

When a woman fails to clinically improve over 48 hours of treatment, she has failed first-line therapy and should be considered to have a complicated mastitis. Concern is for a resistant organism(s), the development of an abscess (or both), or an underlying cancer. Physical examination, cultures of the affected skin area and of the milk, possibly an ultrasound, and a change in antibiotics are indicated.


Approximately 10% of mastitis infections will progress to abscess. The mainstay of management is incision and drainage. Risk factors for abscess formation include: delay in evaluation and treatment, treatment failures from antibiotic resistance, failure to complete antibiotic course, or failure to empty the breast on the affected side. Ultrasound should be performed to help localize an abscess, or in the setting of a palpable abscess can identify multiple pus collections. Further, women who do not respond to appropriate antibiotic treatment should have an ultrasound to search for a concealed abscess.

Treatment requires drainage. This may be accomplished by simple aspiration using ultrasound guidance if the abscess cavity is close to the skin and the overlying skin appears normal. Serial aspirations may be required, although most do not require more than 2 to 3 aspirations. In time, the fluid aspirated will become more serous, and then turn to milk.

However, if the skin overlying the abscess is involved (thin, shiny, and necrotic) a mini-incision and drainage is recommended. Ultrasound may be used to help identify the point of maximum fluctuation. Any necrotic skin should be excised. Copious irrigation should be performed and repeated every 2 to 3 days until there is no further pus noted. This wound will heal by secondary intent and does not require packing.

Overall risk of recurrence is between 5% and 10%. Risk factors for recurrence include a delay in or inadequate treatment, poor feeding technique, Candida infection, and any inherent anatomic abnormalities (ductal abnormality, cyst or tumor). Recurrent infections are more likely to be polymicrobial.

Resistant organisms/MRSA

Several case series report an increase in MRSA-related mastitis. If a woman has had little response to first-line therapy and the comprehensive workup eliminates an abscess, empiric treatment for MRSA is a reasonable alternative pending culture results. Further, anaerobic infections may require broader antibiotic coverage.

Unusual complications

Lesions that do not respond to drainage and antibiotic treatment should be biopsied to rule out carcinoma. Women with prior breast surgery may require specialized care and, at the least, require very close follow-up. Women with a history of breast reduction surgery, breast augmentation with implants, excisional biopsies, and lumpectomies should be considered as having a more complicated mastitis. Toxic shock syndrome is a rare complication that can occur posttreatment as a result of systemic toxin release. This requires prompt recognition and treatment. In these cases, consultation with infectious disease specialists may be helpful.

5. Prognosis and outcome

Most cases of mastitis are self-limited. It is recommended for women to complete a 10- to14-day course of antibiotics and continue nursing throughout. Women with mastitis are at high risk for discontinuation of feeding and should be given additional support and encouragement. It must be emphasized that continued feeding, even while on antibiotics, does not pose a risk to the infant. Even in the setting of an abscess requiring irrigation and drainage, most women heal very well without any residual scar or malformation.

Women who have had mastitis in one pregnancy may be at higher risk to have a recurrence in a subsequent pregnancy. They should be vigilant about feeding practices and seek care if they experience symptoms. It is important for women with mastitis to have good follow-up until resolution of their symptoms. If they have persistent problems, they should be further evaluated for other causes. Women diagnosed with MRSA infection should be followed as they may become colonized with this bacteria.

6. What is the evidence for specific management and treatment recommendations

“World Health Organization. Mastitis: causes and management. WHO, Department of Child and Adolescent Health and Development, 2000”. (This report from the WHO provides information regarding breastfeeding goals and ways that we can help women succeed. Specific information is provided regarding incidence and pathophysiology.)

Akali, AU, McArthur, P. “Complications of breast implants associated with pregnancy”. J Plast Reconstr Aesthet Surg. vol. 61. 2008. pp. 1413-15. (This article reviews three cases of postimplant–associated infections and complications in pregnancy. The authors note that this can pose a unique set of risk factors for women and can be challenging to manage.)

Amir, LH, Cullinane, M. “The role of micro-organisms ( and ) in the pathogenesis of breast pain and infection in lactating women: study protocol”. BMC Pregnancy Childbirth. vol. 11. 2011. pp. 54(The CASTLE (Candida and Staphylococcus Transmission: Longitudinal Evaluation) study was recently completed in Australia. This study aims to better characterize the role of nasal, skin (nipple), and vaginal bacterial colonization in the development of mastitis. This study recruited primiparous mom/baby couplets at delivery and collected bacterial swabs from the pair at that time and out to 6 weeks postpartum. With the rise of community-acquired MRSA this is a question of increasing clinical relevance.)

Bodley, V, Powers, D. “Long-term treatment of a breastfeeding mother with fluconazole-resolved nipple pain caused by yeast: a case study”. J Hum Lact. vol. 13. 1997. pp. 307-11. (This case report follows a breastfeeding mother with cracked nipples undergoing antibiotic treatment (dicloxacillin) for mastitis, who was found to have nipple candidiasis as well.)

Crepinsek, MA, Crowe, L. “Interventions for preventing mastitis after childbirth”. Cochrane Database Syst Rev. vol. 10. 2012. (This review evaluated data from five RCTs concerning prevention strategies for mastitis, including breastfeeding education, pharmacologic treatments, and alternative therapies. However, the investigators found no significant differences, and recommended further standardization of practices and more research.)

David, MZ, Daum, RS. “Community-associated methicillin-resistant : Epidemiology and clinical consequences of an emerging epidemic”. Clin Microbiol Rev. vol. 23. 2010. pp. 616-87. (This review outlines general facts and risk factors for varying types of MRSA-associated infections and epidemiology of this bacteria.)

Dixon, JM, Khan, LR. “Treatment of breast infection”. BMJ. vol. 342. 2011. pp. 484-89. (Reports on the treatment of breast infection with an emphasis on breast abscess.)

Lee, IW, Kang, L. “Puerperal mastitis requiring hospitalization during a nine-year period”. Am J Obstet Gynecol. vol. 203. 2010. pp. 332(This group from Taiwan reported on 127 patients admitted for mastitis between 2000 and 2008.)

Moazzez, A, Kelso, RL. “Breast abscess bacteriologic features in the era of community-acquired methicillin-resistant epidemics”. Arch Surg. vol. 142. 2007. pp. 881-84. (This 2007 study is a case series from a community emergency department of 46 women presenting with a breast abscess. The authors note a 9-fold increase in postpartum mastitis infections associated with MRSA within the previous 5 years.)

Smith-Levitin, M, Skupski, DW. “Antepartum mastitis: a case report”. Infect Dis Obstet Gynecol. vol. 3. 1995. pp. 34-6. (This is a case report of a 14-year-old patient presenting at 29 weeks gestation with bilateral antepartal mastitis. The authors outline additional risk factors for antepartum infection. Although rare, this condition requires early recognition, a search for predisposing factors and causative organisms, and aggressive treatment.)

Stafford, I, Hernandez, I. “Community-acquired methicillin-resistant among patients with puerperal mastitis requiring hospitalization”. Obstet Gynecol. vol. 112. 2008. pp. 533-37. (This article reports the Parkland Hospital Dallas experience with 127 women with mastitis from 1997 to 2005. The authors describe demographics, epidemiology, and the infectious and complication profile of these women.)

Walls, D. “Herbs and natural therapies”. International Journal of Childbirth Education. vol. 24. 2009. pp. 29-37. (There is a paucity of medical literature on the use of herbs, plant extracts, and other products. This is a fairly comprehensive review written by an RN and lactation consultant about which herbs and natural therapies, such as essential oils, can be helpful in managing the symptoms of mastitis and other pregnancy complaints.)

Ip, S, Chung, M. “Breastfeeding and Maternal and Infant Health Outcomes in Developed Countries”. AHRQ Publication No. 07-E007. (This monograph evaluates the data on 23 prespecified infant and maternal outcomes from a review of 86 papers and makes conclusions regarding the quality and strength of evidence. Published in 2007, we are awaiting an update as the evidence evolves.)