How common are they?

Mastitis or inflammation of the breast is a common condition in people who are breastfeeding or lactating. The incidence has been reported as between 3% - 20% in the first 6 months after birth. Most cases occur in the first six weeks but can occur at any time during lactation or pregnancy.

Approximately 3 to 11% of cases of acute mastitis develop into a breast abscess (Mitchell et al., 2022).

Clinical definition of infective mastitis

  • Tender, hot, swollen, wedge-shaped area of breast
  • Skin may be red, shiny and tight with red streaks
  • Temperature of 38.5°C or over
  • Chills
  • Headache
  • Flu-like symptoms
  • Systemic illness

Predisposing factors

  • Nipple damage
  • History of problems with latching the baby on the breast
  • Stress and exhaustion
  • Missed feedings and milk stasis
  • Previous mastitis history with other babies (identified by Foxman et al)
  • Use of a manual breast pump (identified by Foxman et al)

The Academy of Breastfeeding Medicine (Protocol 36) note that the World Health Organization recommend breast-milk-culture and sensitivity testing if there is no improvement after 48 hours of first-line therapy, if the mastitis recurs, or in severe and unusual cases.

Treatment and management

Mastitis as a term signifies any inflammation of the breast and this may not involve a bacterial infection.

Redness, discomfort and a blocked area of the breast may be present in the absence of infection.

In the absence of systemic signs, conservative treatment involves continuing breastfeeding, making sure breast milk is removed from the breast frequently and regularly (which may involve hand or manual pump expressing if the baby is not feeding well), resting and application of cold to the affected area.

Effective treatment and support for breastfeeding continuance are essential. Failure to remove milk from the affected breast may predispose the breastfeeding person to a lactation abscess.


  • Encourage effective and frequent milk removal.
  • Advise to begin feeding on the unaffected breast if pain is inhibiting let-down of milk.
  • Advise to switch to the affected breast after milk let-down.
  • Advise gentle breast massage of the affected area during expression or breastfeeding.
  • Advise continuation of breastfeeding.
  • Advise rest.


A nonsteroidal anti-inflammatory drug (NSAID) can reduce swelling and inflammation therefore providing symptomatic relief. Paracetamol can also provide analgesia.

Also consider ice/cold packs for symptomatic relief of the affected area. The therapeutic benefit is derived from vasoconstriction due to cold.


Antibiotic therapy is reserved for cases of bacterial mastitis.

Bacterial mastitis represents a progression from ductal narrowing and inflammatory mastitis to an entity necessitating antibiotics or probiotics to resolve. Common organisms in lactational mastitis include Staphylococcus (e.g., S. aureus, S. epidermidis, S. lugdunensis, and S. hominis) and Streptococcus (e.g., S. mitis, S. salivarius, S. pyogenes, and S. agalactiae).

First line treatment

  • Dicloxacillin or flucloxacillin 500 mg QID for 10–14 days
  • Where dicloxacillin and flucloxacillin are not available, cloxacillin can be used alternatively; however, oral bioavailability is more variable with cloxacillin. All drugs have low Relative Infant Dose of the drug.
  • Cephalexin 500 mg QID for 10–14 days
  • Broader coverage including gram negative rods; does not need to be taken separately from meals

Second line treatment

  • Clindamycin 300 mg four times daily for 10–14 days
  • Trimethoprim-sulfamethoxazole DS BID for 10–14 days

Not recommended for breastfeeders of children with G6PD deficiency. Use with caution in breastfeeding people with premature infants or infants with hyperbilirubinemia, especially under 30 days old.

Oral antibiotics may not be appropriate in severe cases of mastitis and admission for IV-antibiotic treatment may be necessary.

Breast abscess

If all the appropriate treatment for mastitis has been given and an area of the breastfeeding person’s breast remains hard, reddened and painful an abscess may have formed or be forming.

In some situations, the breastfeeding person may be feeling well again due to the antibiotic treatment and breast drainage and pyrexia may have resolved.

Diagnosis and treatment

A breast ultrasound may identify the abscess area.

Appropriate initial treatment is likely to be needle aspiration with fluid culture which may require repeating.

If there are multiple abscesses or if the abscess is large or unresponsive to repeated aspiration treatments, surgical drainage is necessary.

The breast will still require milk drainage and in many cases breastfeeding continues after the surgical drainage when the person is on further antibiotic treatment.