Mastitis is inflammation in the breast caused by milk stasis — when the breast isn't being fully drained, or isn't drained often enough. The single best way to prevent it is responsive feeding on demand rather than to a schedule. It can often be treated without antibiotics, but a fever or flu-like symptoms need urgent medical attention, because mastitis can progress quickly to an abscess or sepsis.
When supporting families with breastfeeding, it's really important to be able to recognise when there are problems and how to resolve them quickly — especially in the case of mastitis. It can be incredibly painful and debilitating for anyone who breast or chestfeeds.
Table of contents
What mastitis is
Mastitis is inflammation in the breast, caused by milk stasis. This occurs when the breast isn't being fully drained or emptied often enough. It can also be caused by damage to the ducts, which makes it difficult for milk to pass through.
Lighter-skinned breasts will often show a red patch, which may be hot to the touch. This may look different on dark or brown-skinned breasts, where redness may not show easily — so don't rely on redness alone. The breast will feel heavy, may have a lump, and the skin may feel tight.
Symptoms of mastitis
Mastitis typically comes on quickly — often within hours. The most common signs are:
- Pain and tenderness in one area of the breast, which may feel like a deep ache or burning sensation
- Swelling and hardness — the affected area may feel firm or lumpy
- Heat — the breast may feel noticeably warmer than usual
- Skin changes — on lighter skin tones, a red patch is common; on dark or brown skin tones, redness may not show at all, so heat and texture changes are more reliable signs
- Flu-like symptoms — fever, chills, aches and fatigue. These are a warning sign that the infection has become systemic and needs urgent medical attention
Mastitis usually affects only one breast at a time. If both breasts are affected simultaneously, it's worth seeking medical advice promptly.
How you get it
Some of the most common causes are:
- Feeding on a regimented schedule instead of responsively, on demand
- Missing a feed, or going an unexpected length of time between feeds
- Poor infant attachment at the breast, preventing effective drainage
- Nipple damage or a nipple fissure
- Damage to the breast or ducts
- Wearing a bra that is too tight
- Smoking
- Suddenly stopping breastfeeding — going "cold turkey"
How to avoid it
The best way to avoid mastitis is to feed the baby responsively, on demand, rather than to a regimented schedule.
Beyond that: make sure bras fit well, and get measured again if you need to be. And try not to stop breastfeeding, or reduce feeds, suddenly.
How to treat it
Mastitis can often be treated without the use of antibiotics.
Seek urgent medical attention if you develop a fever, lethargy or other flu-like symptoms. Mastitis can turn quickly into sepsis or an abscess.
It's important to keep feeding on the affected breast where possible. You can also try:
- Simple pain relief such as paracetamol or ibuprofen
- Cold compresses applied to the breast to reduce inflammation and relieve discomfort
If symptoms are not improving or are getting worse after 24 hours of self-care, seek medical advice. A GP or midwife can assess whether antibiotics are needed. If mastitis keeps recurring, it's worth a full feeding assessment to find out why the breast isn't draining properly — position and attachment and tongue-tie are both common underlying causes. You can find an IBCLC through Lactation Consultants of Great Britain.
To help prevent recurrence: maintain good breastfeeding technique, ensure good hygiene, and address any nipple damage or attachment issues early.
How mastitis progresses: when to act fast
Mastitis can move through three stages, and knowing where someone is on that spectrum helps practitioners advise families correctly.
Stage 1: Milk stasis. The breast isn't draining fully. There may be a hard area or lump, and the breast feels uncomfortable. No infection yet. Responsive feeding, warm compresses and gentle massage will usually resolve this within 12–24 hours.
Stage 2: Inflammatory mastitis. The inflammation has intensified. The breast is painful, hot and swollen, and the person may feel generally unwell. Continued feeding and supportive measures (cold compress, pain relief) are still appropriate, but if symptoms haven't improved or are worsening after 24 hours, they should see a GP or midwife. This is the point at which antibiotics may be indicated.
Stage 3: Infective mastitis or abscess. Bacteria have entered through a crack or damaged duct. A fever, flu-like symptoms, or a fluctuant lump (one that feels soft in the centre) indicates this stage. This requires immediate medical attention. Antibiotics are usually prescribed; if an abscess has formed, drainage may be needed. It is still safe — and important — to continue breastfeeding through this.
Practitioners working with breastfeeding families should feel confident helping someone identify which stage they're at and when to escalate to medical care. This kind of clinical reasoning is covered in depth in Babyem's maternity nurse training.
Common questions
Should you keep breastfeeding with mastitis?
Yes. Continuing to feed on the affected breast helps clear the milk stasis that caused it in the first place.
Does mastitis always need antibiotics?
No — it can often be resolved without them. But a fever, lethargy or flu-like symptoms need urgent medical attention.
What does mastitis look like on darker skin?
The redness that shows on lighter skin may not be visible. Look instead for heat, heaviness, a lump, and tight-feeling skin.
Can a tight bra cause mastitis?
Yes. A bra that is too tight is a recognised cause, because it restricts drainage. Get remeasured if you're unsure of your fit.
Clinical references
About the author
Charlotte Treitl is an International Board Certified Lactation Consultant and a Babyem tutor, supporting families with infant feeding and teaching practitioners how to recognise and resolve feeding problems early.
Need hands-on support at home?
A Babyem-trained maternity nurse can support you and your baby in the first weeks, including with feeding, settling and newborn care. Our placement scheme connects families with experienced, accredited practitioners.
Learn to spot feeding problems early
Babyem's accredited training teaches practitioners how to assess feeding, recognise problems like mastitis and tongue-tie, and refer confidently.