Mastitis & Breast Abscess

by Dr Clare Macdonald, General Practitioner

I went to the doc regarding recurring mastitis. He didn’t seem too concerned and then said:

  1. Culturally in the UK breastfeeding stops at 6 months (even if that’s true, which I’m not sure it is, I don’t think that should actively encouraged if breastfeeding is going well)
  2. That as I breastfed of course I would get mastitis (I know plenty of mums who have breastfed without mastitis!)
  3. He said babies find it hard to wean off breastfeeding after 1 year (a breastfeeding counsellor I spoke to afterwards refuted this).

He seemed nice enough but completely misinformed.

Anon, Mother

Mastitis occurs commonly in lactating women, with estimated rates in the range 3-20%1. It is most likely in the second and third weeks following delivery but can occur at any time2, and so should be considered in any woman presenting with breast pain or breast skin colour changes, particularly when in association with systemic symptoms.

Mastitis can be viewed as a continuum from engorgement through to breast abscess1, and classified as non-infectious or infectious3Milk stasis is the commonest underlying cause of mastitis, and this can progress to infection, particularly when there is nipple trauma. Any reason for ineffective or incomplete milk removal therefore increases the risk of mastitis. These include:

  • Suboptimal attachment at the breast
  • Physical problem with the infant’s mouth (eg. tongue-tie, cleft lip)
  • Nipple pain (prompting the mother to be reluctant to feed, or to favour the less painful breast)
  • Limiting the time baby spends at the breast
  • Physical pressure on the breast, eg. from tight bra or clothing
  • Sudden reduction in feeding frequency (eg. mother returning to work, or baby sleeping for longer at night)

Women who have had mastitis are at increased risk of recurrent episodes. Reasons for this include inadequate treatment for the previous episode, Staph. aureus carriage and not correcting predisposing factors for milk stasis3.

Mastitis is sometimes associated with nipple damage or fissure. The two are thought to coexist because both are commonly caused by poor attachment at the breast, as well as the fissure providing an entry point for infection1.


  • Breast pain
    • often unilateral
    • often affecting a defined area of the breast
    • pain is often worse before feeding and may feel improved after feeding
    • however the pain can be more intense during feeding, particularly at letdown
  • Malaise
  • Flu-like symptoms
  • Fever


  • Firm breast swelling
    • often, but not necessarily, in a wedge-like defined area
    • +/- increased redness of the overlying skin (erythema may not be evident in darker skin tones or it may appear instead as hyperpigmentation or colour changes observed by the patient)
  • In some cases a nipple fissure may be evident
  • Pyrexia


Diagnosis is usually clinical and milk culture is not recommended routinely in primary care by NICE CKS. Situations in which to send breast milk for microscopy, culture and sensitivity are when mastitis is severe or recurrent, hospital acquired infection is suspected or there is a deep ‘burning’ pain (which may be suggestive of ductal infection). The NICE CKS page provides information on how breast milk samples should be collected.


General, supportive measures are important; encouraging adequate maternal fluid intake and use of simple analgesia eg. paracetamol and/or ibuprofen, both of which are safe in breastfeeding. A warm compress placed on the breast, or bathing in a warm bath or shower can be beneficial.

Effective milk removal is key in the management of mastitis.  This can be done by:

  • Encouraging ongoing breastfeeding, including from the affected breast
  • Ensuring that positioning and attachment are optimal – involve a breastfeeding specialist to help with this if needed
  • Avoiding long gaps between feeds
  • Applying a warm compress to the breast before feeds
  • Massage lumpy areas of the breast
  • Expressing after feeds to further empty the breast when breastfeeding and massage has not softened the affected area (avoid routine expressing as this may contribute to increasing milk supply and exacerbate the mastitis)

Antibiotics should be prescribed when:

  • There is a nipple fissure that is infected
  • There is worsening of symptoms, or no improvement after 12-24 hours of measures to promote effective milk removal
  • There is microbiological evidence of infection (rarely available)

The antibiotic of choice is usually flucloxacillin 500mg QDS for 10-14 days, although local antimicrobial guidance should be followed, and allergies considered. See our page on ‘Drugs in Breastmilk for more information on the safety of different antibiotics in breastfeeding women.

In rare cases, mastitis can result in severe infection and sepsis. When signs of sepsis or rapidly progressing infection are evident, emergency hospital admission should be arranged (see The UK Sepsis Trust GP Maternal Sepsis Decision Support Tool).

In order to reduce the risk of future episodes, predisposing factors should be addressed and women educated about methods to ensure effective milk removal. Where there is a suspicion that the latch is not optimal, access to appropriate trained breastfeeding support should be made available. If the woman does not wish to continue breastfeeding, give advice on stopping breastfeeding, for example avoiding abrupt cessation.

Breast Abscess

In around 3% of women with mastitis, an infective area will localise and an abscess will develop4. This can either happen as part of an acute episode or after a course of appropriate treatment. There is typically a well-defined, firm, extremely tender swelling +/- redness or hyperpigmentation (depending on skin tone), sometimes with overlying oedema. If an abscess is suspected, urgent hospital referral should be arranged (same day discussion with breast/general surgeons). They are typically managed by ultrasound guided aspiration, or, in some cases incision and drainage under general anaesthetic.

A woman with a breast abscess should be reassured that she is likely to fully recover and is able to continue breastfeeding without causing harm to the baby. The WHO are clear that doctors and other healthcare workers should explain how this can be achieved and facilitate ongoing breastfeeding2.

Risk to the Infant

Even in cases where breast milk contains pus, or Staph. Aureus is present, the WHO advice based on a number of studies is that ongoing breastfeeding during mastitis is generally safe. The only exception to this is when a mother is HIV-positive, in which case she should avoid feeding from the affected side until fully recovered2.

The US Centre for Disease Control advises temporary postponement of breast/breastmilk feeding if a mother with Hepatitis B or C has active nipple bleeding5.

Further Information


  1. Amir L, Academy of Breastfeeding Medicine Protocol Committee. ABM clinical protocol #4: Mastitis, revised March 2014. Breastfeed Med. 2014;9(5):239–243.
  2. Mastitis Causes and Management WHO Geneva 2000
  3. NICE CKS Mastitis and Breast Abscess: Background Information. Revised October 2018
  4. Amir L, Forster D, McLachlan H, Lumley J. Incidence of breast abscess in lactating women: report from an Australian cohort. BJOG: An International Journal of Obstetrics and Gynaecology. 2004;111(12):1378-1381.
  5. US Centres for Disease Control and Prevention (CDC): Breastfeeding & Hepatitis B or C Infection Updated June 2015

Published April 2017, Updated August 31st 2020