Acute mastitis !
Acute mastitis is inflammation of the breast, usually during breastfeeding, causing a painful, red, warm area and often fever.
Updated 2026-10-29
Structures involved
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In histology
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Why it happens
What it is
Inflammation of the breast, usually during breastfeeding, that causes a painful, red, warm area and often fever. It ranges from inflammation due to milk stasis to bacterial infection.
Who gets it
Common in breastfeeding women, mostly in the first weeks to months after birth. Non-lactational forms (periductal and granulomatous mastitis) are less frequent.
Causes
- Milk stasis from poor emptying of the breast
- Bacterial infection, mostly Staphylococcus aureus (including methicillin-resistant strains)
- Nipple cracks that let bacteria in
- Non-lactational: periductal mastitis (linked to smoking), idiopathic granulomatous mastitis
Risk factors
- Poor latch or infrequent feeding
- Nipple damage
- Abrupt weaning or missed feeds
- Oversupply of milk
- Tight bras or pressure on the breast
- Previous mastitis, maternal fatigue
Pathophysiology
When milk is not removed well, ducts and alveoli become engorged and the surrounding tissue becomes inflamed. Bacteria from the skin or the baby's mouth can enter through damaged nipples and infect the stagnant milk. Untreated infection can form a localised abscess.
Classification
- Lactational or non-lactational
- Inflammatory (non-infectious) or infectious
- Spectrum in recent guidance: ductal narrowing, inflammatory mastitis, bacterial mastitis, phlegmon, abscess
Symptoms and signs
- Painful, tender, often wedge-shaped red area of one breast
- Warmth and swelling
- Fever, chills and flu-like malaise
- Pain during feeding
Diagnosis
- Clinical
- Usually clinical: a breastfeeding woman with a tender, red area and systemic symptoms.
- Tests
- Milk culture when severe, recurrent, hospital-acquired or not responding to treatment; blood tests if sepsis is suspected.
- Imaging
- Breast ultrasound when an abscess is suspected or symptoms do not improve; imaging or biopsy to exclude cancer in non-lactational or persistent cases.
Differential diagnosis
- Breast engorgement
- Blocked duct
- Breast abscess
- Inflammatory breast cancer
- Galactocele
Goal of treatment
Relieve pain and inflammation, clear any infection and keep milk flowing, so breastfeeding can continue and abscess is prevented.
Treatment
- Conservative
- Clinical principle: continue breastfeeding or expressing from the affected breast; it is safe for the baby and helps recovery. Good latch, cold compresses, supportive bra; current guidance avoids deep massage.
- Medical
- Simple analgesics and non-steroidal anti-inflammatory drugs compatible with breastfeeding.
- Medical
- Antibiotics active against Staphylococcus aureus (penicillinase-resistant penicillins or first-generation cephalosporins, with alternatives for allergy or MRSA) when symptoms persist or infection is likely.
- Follow-up
- Review if no improvement; ultrasound to look for an abscess; lactation support to prevent recurrence.
Complications
- Breast abscess
- Early, unplanned weaning
- Recurrent mastitis
- Sepsis (rare)
Prognosis
Usually resolves quickly with good milk removal and, when needed, antibiotics. Stopping breastfeeding suddenly increases the risk of abscess.
Prevention
- Good latch and frequent, effective feeding
- Early care of nipple damage
- Gradual rather than sudden weaning
- Breastfeeding education and support
Test yourself
Think of the answer, then tap the question to see it.
Should breastfeeding continue during lactational mastitis?
Yes; continuing to breastfeed or express is safe for the baby and helps clear the breast and prevent abscess.
Which organism most often causes infectious mastitis?
Staphylococcus aureus, including methicillin-resistant strains.
When is breast ultrasound indicated in mastitis?
When an abscess is suspected or symptoms do not improve with treatment.
Which diagnosis must be excluded in persistent mastitis in a non-lactating woman?
Inflammatory breast cancer.
Related conditions
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Acute Mastitis (StatPearls (NCBI Bookshelf), 2024).
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