01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Mastitis during breastfeeding begins when milk removal and local tissue capacity become mismatched. Alveolar distension, ductal narrowing and stromal oedema produce inflammation; damaged nipple skin and altered milk microbiota may permit bacterial infection, commonly involving staphylococci. The patient may develop a focal red tender region, fever, myalgia and difficulty feeding, but inflammation alone does not automatically require antibiotics.
Early care protects both maternal health and breastfeeding. Comfortable on-demand feeding, correction of positioning and analgesia help resolve milk stasis without stimulating greater production. Antibiotics are added for clear bacterial features, persistent or worsening symptoms after effective self-care, or significant illness. A localised collection requires ultrasound and drainage because antibiotics penetrate poorly into undrained pus. Persistent erythema or mass after appropriate treatment reopens the differential rather than prompting endless antibiotic courses.
Key points
- Lactational mastitis is a spectrum from milk stasis and sterile inflammation to bacterial infection, usually with focal breast pain, erythema and systemic influenza-like symptoms.
- Ask about abrupt feed changes, oversupply, pressure, ineffective attachment, nipple trauma and prior antibiotics; examine for a wedge-shaped inflamed area and a discrete collection.
- Continue comfortable breastfeeding and avoid abrupt weaning; express only enough to maintain physiological drainage when direct feeding is not possible, because aggressive over-emptying can worsen oversupply and oedema.
- Use cold packs, rest, fluids and compatible simple analgesia; urgent lactation support should correct attachment and tissue trauma rather than instructing painful massage.
- NHS Dumfries & Galloway guidance uses oral flucloxacillin 500 mg four times daily for 10–14 days when bacterial mastitis requires antibiotics, with allergy alternatives determined from reaction history and local guidance.
- Review response by about 48 hours; obtain ultrasound and culture for a persistent mass, worsening illness, recurrent disease or treatment failure, and exclude inflammatory cancer when the pattern does not resolve.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Milk stasis and oedema
Missed or ineffective feeds, abrupt weaning, oversupply and external pressure increase intralobular milk volume and surrounding tissue oedema.
Bacterial entry and dysbiosis
Nipple fissures and disrupted local microbiota permit bacterial proliferation, commonly staphylococci, within inflamed lactating tissue locally.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Alveolar distension
Accumulated milk raises local pressure, narrows small ducts and impairs capillary and lymphatic flow, generating pain and swelling.
- 2Inflammatory cascade
Tissue stretch and milk extravasation recruit cytokines and leukocytes, producing warmth, erythema, fever and systemic malaise even before bacterial invasion.
- 3Suppuration
Progressive bacterial infection causes tissue liquefaction and a walled fluid collection that requires drainage in addition to antimicrobial therapy.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
A tender warm erythematous region, often wedge shaped, accompanies fever, chills or myalgia. Erythema may be less visible in darker skin, making warmth, swelling and tenderness important.
Missed feeds, abrupt weaning, oversupply, pressure from clothing or ineffective attachment can precede symptoms. Ask what changed before assuming poor hygiene or maternal fault.
Persistent high fever, worsening local signs, purulent nipple trauma or failure to improve after supportive care increases the likelihood that antibiotics are needed.
A persistent focal mass, fluctuation or recurrent fever despite therapy suggests abscess or phlegmon. Clinical palpation cannot define drainable fluid reliably.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Feeding observationFirst step - Why
- Identify ineffective attachment, painful compression and modifiable milk-transfer problems.
- Interpretation and limitations
- Observe a real feed with consent and appropriate expertise. Nipple shape after feeding and infant swallowing give practical evidence; blame-based advice does not correct technique.
- 02
Targeted breast ultrasound - Why
- Identify abscess, phlegmon or galactocele when a mass persists or response is poor.
- Interpretation and limitations
- A drainable fluid cavity changes treatment. Diffuse inflammatory change without collection supports continued medical and feeding management but does not exclude later evolution.
- 03
Milk or pus culture - Why
- Guide therapy in severe, recurrent or non-responsive infection and after drainage.
- Interpretation and limitations
- Collect before a new antibiotic when feasible without delaying urgent treatment. Interpret growth with contamination risk and clinical response; resistance may explain treatment failure.
- 04
Clinical sepsis assessment - Why
- Detect organ dysfunction and decide whether outpatient treatment is safe.
- Interpretation and limitations
- Record full observations, hydration and mental state. Tachycardia may reflect pain or fever, but hypotension, confusion or rising respiratory effort requires urgent escalation.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Breast abscess
Persistent fluctuant mass, recurrent fever and poor treatment response suggest organised pus and require ultrasound and source control.
Galactocele
A milk-retention cyst causes a focal lactational mass with less systemic inflammation, though secondary infection can create overlapping signs.
Inflammatory breast cancer
Diffuse erythema, oedema and peau d’orange that fail to resolve with appropriate infection management require urgent imaging and tissue diagnosis.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Early inflammation pathwayRestore comfortable physiological feedingFirst stepA breastfeeding parent has 12 hours of focal tenderness and mild fever after several missed feeds, without a mass or systemic instability.+
- 1Assess observations, hydration, breast and nipple, then watch attachment or arrange same-day lactation expertise to identify ineffective transfer or painful compression.
- 2Encourage continued comfortable feeding according to infant cues and hand expression only for comfort if needed; avoid deep massage and repeated pumping intended to empty the breast completely.
- 3Use a cold pack after feeding, oral fluids, rest and compatible analgesia, while explaining the signs that suggest bacterial progression or abscess.
- 4Arrange review within 12–24 hours if symptoms do not clearly improve and sooner for spreading erythema, vomiting, marked fever or a new focal mass.
02Bacterial mastitis pathwayAdd a complete antimicrobial courseSymptoms are worsening after 24 hours of effective supportive care, with fever and an infected nipple fissure but no collection on examination.+
- 1Check immediate and delayed penicillin reactions, hepatic and renal history, previous resistant organisms and current medicines before selecting treatment.
- 2Prescribe flucloxacillin 500 mg orally four times daily for 10–14 days under the cited NHS Dumfries & Galloway pathway, explaining timing, adherence and common gastrointestinal effects.
- 3Continue breastfeeding and monitor the full-term healthy infant for diarrhoea, oral thrush, rash or poor feeding as advised by SPS for penicillins.
- 4Review at about 48 hours; worsening illness, absent response or a persistent lump triggers culture, ultrasound and specialist breast input rather than automatic repetition.
03Recurrent or atypical pathwayLook beyond another identical prescriptionA third episode occurs in the same quadrant and the area never became completely normal between courses.+
- 1Confirm previous diagnoses, culture results, adherence and whether ultrasound ever demonstrated a collection or structural lesion.
- 2Obtain targeted imaging and culture before further treatment when the patient is clinically stable, and assess diabetes, immune compromise and nipple trauma.
- 3Resolve oversupply and attachment drivers with lactation support while the breast team excludes abscess, duct lesion, granulomatous mastitis and inflammatory carcinoma.
- 4Document complete clinical resolution or a tissue diagnosis and provide a plan for rapid review if the same focal abnormality returns.
Key medicines and prescribing safety1 treatment · regimens, roles and cautions+
Flucloxacillin
For a stable adult with bacterial lactational mastitis and no relevant contraindication, NHS Dumfries & Galloway specifies flucloxacillin 500 mg orally four times daily for 10–14 days. Take the selected Flamingo 500 mg capsules at least one hour before or two hours after food, with a full 250 mL glass of water; remain upright immediately afterwards.Do not use with hypersensitivity to this product or beta-lactam antibiotics, or previous flucloxacillin-associated jaundice/hepatic dysfunction. Clarify serious delayed reactions as well as immediate allergy. At CrCl below 10 mL/min, obtain a prescriber decision on dose reduction or a longer interval before using the standard schedule; dialysis does not require a supplementary dose. Use caution with existing liver dysfunction. Review methotrexate toxicity, warfarin/INR when starting or stopping, probenecid and reduced voriconazole exposure. With concurrent paracetamol, severe renal impairment, sepsis or malnutrition increases high anion gap metabolic acidosis risk, especially at maximal paracetamol doses: review the combination and arrange risk-based monitoring. SPS compatibility applies to healthy term infants; monitor diarrhoea, thrush, rash and poor feeding.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Breast abscess
Untreated or non-responsive bacterial mastitis may progress to a drainable collection, prolonging illness and disrupting feeding.
Premature breastfeeding cessation
Pain, conflicting advice and fear about medicines can lead to avoidable weaning, engorgement and psychological distress.
Recurrent focal inflammation
Uncorrected oversupply, attachment problems, resistant bacteria or an underlying structural lesion can cause repeated same-site episodes.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Recheck maternal temperature, pulse, hydration, erythema extent, pain and ability to feed or express within the agreed interval.
- Assess whether the affected area softens after comfortable feeding without escalating pumping that drives continued oversupply.
- At 48 hours after antibiotics, confirm clear improvement and review culture if obtained; absent response triggers ultrasound and diagnostic reconsideration.
- Ask about infant diarrhoea, oral thrush, rash and feeding while a penicillin is used, particularly if the infant was premature or unwell and needs specialist advice.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Inflammation precedes infection
Milk stasis and tissue oedema can cause feverish symptoms before bacterial infection is established. Early mechanical and anti-inflammatory care can prevent unnecessary antibiotics.
More pumping can worsen physiology
Repeated complete emptying signals greater milk production and may perpetuate oversupply. Expressing for comfort differs from using a pump aggressively after every feed.
Massage can injure tissue
Deep forceful massage of an oedematous breast may increase microvascular and lymphatic injury. Gentle handling and correction of feeding mechanics are safer.
Persistent redness changes the diagnosis
Inflammatory breast cancer is uncommon during lactation but clinically important. A non-resolving mass or erythema after adequate infection care needs specialist imaging and tissue assessment.
11Common pitfallsFrequent interpretation and management errors.
- 01
Advising abrupt cessation of breastfeeding increases milk stasis and can worsen symptoms while threatening the feeding relationship.
- 02
Prescribing antibiotics at the first mild inflammatory symptom ignores self-limiting milk-stasis disease and antimicrobial stewardship.
- 03
Continuing repeated high-volume pumping after every feed can maintain oversupply and the inflammatory cycle.
- 04
Repeating antibiotics without ultrasound for a persistent mass can leave an abscess or malignant mimic undiagnosed.