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# 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

Tap one to see what it is and open it in 3D.

- [Mammary gland lobes](https://durgical.com/en/anatomy/mammary-gland/)
- [Lactiferous ducts](https://durgical.com/en/anatomy/lactiferous-ducts/)
- [Nipple](https://durgical.com/en/anatomy/nipple/)
- [Areola](https://durgical.com/en/anatomy/areola/)
- [Breast fat](https://durgical.com/en/anatomy/body-of-breast/)

## In histology

- [Breast: ducts, lobules and changes with life stage](https://durgical.com/en/histology/breast-ducts-lobules-and-changes-with-life-stage/)

## In the clinical exam

- [Clinical breast examination](https://durgical.com/en/clinical-exam/clinical-breast-examination/)

## In physiology

- [Lactation](https://durgical.com/en/physiology/lactation/)

## Why it happens

- [Patterns of acute inflammation: serous, fibrinous, purulent, abscess, ulcer](https://durgical.com/en/general-pathology/patterns-of-acute-inflammation-serous-fibrinous-purulent-abscess-ulcer/)

## 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](https://durgical.com/en/anatomy/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](https://durgical.com/en/anatomy/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

## Red flags

- Fluctuant or persistent mass (abscess)
- Signs of sepsis: high fever, tachycardia, hypotension
- No improvement after appropriate treatment
- Inflammation in a non-lactating woman or that does not resolve (inflammatory breast cancer)

## 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.

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## Related conditions

- [Breast abscess](https://durgical.com/en/conditions/breast-abscess/)
- [Breast cancer](https://durgical.com/en/conditions/breast-cancer/)
- [Fibrocystic breast changes](https://durgical.com/en/conditions/fibrocystic-breast-changes/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Acute Mastitis](https://www.ncbi.nlm.nih.gov/books/NBK557782/) (StatPearls (NCBI Bookshelf), 2024).

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Source: https://durgical.com/en/conditions/acute-mastitis/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/acute-mastitis/