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Labor & postpartum Call your provider

Mastitis

Also known as Breast infection, Lactation mastitis. Postpartum, usually in the first weeks of breastfeeding.

Mastitis inflames the breast, often with infection, and most commonly strikes in the early weeks of breastfeeding. It comes on fast: a red, hot, painful wedge on one breast, often with a fever and flu-like aching that can leave you suddenly and thoroughly unwell. It is miserable but very treatable, and the headline is this: keep breastfeeding. Nursing or expressing on the affected side helps clear it, and your milk is safe for your baby.

Know the warning signs When to call a provider
How common
Up to about 1 in 10
Affects roughly 7% to 10% of breastfeeding parents in the US, and more worldwide.
When
Early breastfeeding
Most common in the first six weeks postpartum, though it can occur any time while nursing.
Urgency
Call your provider
Treated at home and often with antibiotics; a high fever or worsening needs a call.
Outlook
Resolves with treatment
Most cases clear quickly with treatment.

Understanding it

What is mastitis?

Mastitis is inflammation of breast tissue that often becomes an infection. It is overwhelmingly a condition of breastfeeding, appearing in the first weeks after birth while nursing is still being established. It usually starts on one breast, a firm, red, warm, tender area, often wedge-shaped, and can escalate within hours to a fever and the body aches, chills, and exhaustion of a flu-like illness.

It usually begins with milk that is not moving well, milk stasis. When milk backs up in part of the breast, from a blocked duct, oversupply, a missed feeding, or a poor latch, the stagnant milk and surrounding tissue become inflamed. Bacteria, often from the skin or the baby's mouth, can then enter through a cracked or sore nipple and turn inflammation into infection.

It feels counterintuitive to nurse from a painful, infected breast, but keeping the milk flowing is central to getting better, and your milk stays safe even if you are on antibiotics. Stopping abruptly only makes mastitis worse, letting milk build up further.

Care combines keeping milk moving with symptom relief: cold compresses for swelling, pain relievers like ibuprofen or acetaminophen, rest, and fluids. Guidance has recently shifted on one point: deep, aggressive massage and forcefully emptying the breast are now discouraged, because they can worsen the inflammation; gentle handling is better. If fever and firm redness persist beyond about a day, you likely need antibiotics. Most mastitis, though, clears quickly once treated.

Symptoms

What are the symptoms?

Mastitis usually affects one breast and combines local signs, a red, hot, painful area, with a systemic, flu-like illness. It can come on quickly.

Early signs

  • A firm, red, warm, and painful area on one breast, often wedge-shaped
  • Breast swelling or a tender lump
  • Pain or a burning feeling, constant or while breastfeeding
  • A fever, often 101 F (38.3 C) or higher
  • Flu-like symptoms: chills, body aches, fatigue, sometimes nausea

Emergency signs — call 911

  • A high fever with worsening breast pain, or feeling very unwell
  • Symptoms that do not improve, or worsen, after about 24 hours of home care or antibiotics
  • A firm, fluctuant lump that persists, which can be an abscess needing drainage
  • Red streaking spreading from the area, or a rapidly enlarging red region
  • Pus or blood from the nipple

Why it matters

Risks to you and baby

Breast abscess

If mastitis is not treated or does not clear, pus can collect into an abscess, a firm, fluctuant lump. It happens in a minority of cases and usually needs draining. A lump that persists after treatment should be checked.

Feeling very unwell

Mastitis can make you feel truly sick, with high fever and exhaustion, just when you are already recovering from birth and caring for a newborn. Prompt treatment gets you better faster.

Early weaning

The pain leads some people to stop breastfeeding, which actually makes it worse and cuts short nursing they may have wanted to continue. Support and effective treatment help you keep going.

Rarely, a serious infection

Very occasionally, an untreated breast infection can spread and make you severely ill. Uncommon, but it is why a high fever with worsening symptoms warrants prompt care.

How it's found

How is it diagnosed?

Mastitis is usually diagnosed from your symptoms and a breast exam. Tests are reserved for cases that do not improve or where an abscess is suspected.

History and breast exam

The classic picture, a firm, red, tender area on one breast with fever and flu-like symptoms, is usually enough to diagnose it clinically.

Breast ultrasound

Used if an abscess is suspected, a lump that persists or symptoms that do not respond, to look for a pocket of pus that needs draining.

Milk culture

If mastitis does not improve on antibiotics, a sample of milk can be cultured to identify the bacteria and check for a resistant organism, guiding a change in treatment.

Whenever you have breast pain with redness and fever. Persistent systemic symptoms beyond about 24 hours warrant evaluation.

Treatment

How is it managed?

Treatment keeps milk flowing, eases symptoms, and adds antibiotics when infection is present.

Treatment paths

Keep breastfeeding or expressing on the affected side; keeping milk moving is the foundation of getting better. For symptoms, use cold compresses to reduce swelling, take a pain reliever like ibuprofen or acetaminophen, rest, and stay hydrated. Recent guidance advises against deep, aggressive massage and against forcefully emptying the breast, which can worsen the inflammation; gentle handling and feeding as your baby needs are better.

Medication

If there are signs of infection, or inflammation does not settle within about a day, antibiotics are prescribed, usually for 10 to 14 days, targeting the skin bacteria involved. Finish the full course even once you feel better. Pain relievers can be used alongside.

Monitoring

Symptoms should start improving within a day or two of starting antibiotics. If they do not, or a lump persists, contact your provider, as this can mean an abscess or a resistant organism.

Can it recur?

Mastitis can recur, especially if the underlying issue, a poor latch, oversupply, or cracked nipples, is not addressed. Improving breastfeeding technique, often with a lactation consultant, and caring for your nipples lower the chance of it returning.

What you can do

Can it be prevented?

  • Keep milk moving

    Feed or express regularly and effectively, and try not to skip feedings or let the breast get overly full, since trapped milk is what starts mastitis. Avoid abrupt weaning; wind down gradually.

  • Get the latch right

    A good latch empties the breast well and protects your nipples. If breastfeeding hurts or feels ineffective, a lactation consultant can help, one of the best ways to prevent mastitis.

  • Care for your nipples

    Cracked or sore nipples are the entry point for bacteria. Treating and protecting them, and correcting what is causing the damage, helps keep infection out.

  • Avoid pressure on the breast

    Tight bras, tight clothing, or steady pressure from a bag strap or sleeping position can block milk flow. Keep things loose and comfortable around your breasts.

Who is more at risk

Risk factors

Cracked or sore nipples
Damaged nipples give bacteria a way into the breast, making them one of the strongest risk factors for mastitis.
Anything that traps milk
A blocked duct, oversupply, skipped feedings, abrupt weaning, or pressure from a tight bra all back milk up and can trigger mastitis.
A poor latch or feeding difficulties
If the baby does not latch or feed well, the breast does not empty properly, leading to the milk stasis that precedes mastitis.
A prior episode of mastitis
Having had mastitis before makes it more likely again, especially if the underlying cause was not addressed.
Being run down
Fatigue, stress, poor nutrition, and smoking all raise the risk, common realities in the demanding newborn period.

Do not wait

When to call your provider or 911

  • Call your provider if you have a high fever with worsening breast pain, or feel very unwell.
  • Reach out if symptoms do not improve, or get worse, after about 24 hours of home care or antibiotics.
  • Seek care for a firm lump that persists, which can be an abscess needing drainage.
  • Contact your provider for red streaking spreading from the area, or pus or blood from the nipple.
  • Ask for help early, including a lactation consultant, if breastfeeding is painful or your latch is off, to prevent recurrence.

Talking to your team

Questions to ask your provider

  • Do I need antibiotics, and if so, which one and for how long?
  • Is it safe to keep breastfeeding, and should I feed more or less on that side?
  • Should I use warm or cold compresses, and should I massage the area?
  • What signs mean this has become an abscess?
  • Can a lactation consultant help me fix what caused this?
  • How can I prevent it from coming back?

Keep reading

More on mastitis

All pregnancy guides articles

Good to Know

Mastitis FAQs

Common questions about mastitis, answered.

Can I keep breastfeeding with mastitis?

Yes, and you should. Continuing to nurse or express on the affected side helps clear mastitis by keeping milk moving. Stopping abruptly lets milk build up and makes it worse. It may hurt at first, but nursing through it is part of getting better.

Do I need antibiotics?

Sometimes. Early, mild mastitis, or a blocked duct, may settle with keeping milk moving, cold compresses, pain relief, and rest. But with signs of infection, a fever and firm redness, or no improvement within about a day, you likely need antibiotics, usually a 10 to 14 day course. Contact your provider to decide, and finish the full course if prescribed.

Should I massage the lump?

Not aggressively. Guidance has recently changed here. Deep, forceful massage and trying hard to empty the breast are now discouraged, because they can worsen the inflammation and swelling. Gentle handling, feeding as your baby needs, and cold compresses are better. If unsure, ask your provider or a lactation consultant.

Is my milk still safe for my baby?

Yes. Your milk is safe to feed even with mastitis and even while you are on antibiotics for it. Your baby will not be harmed by nursing from the affected breast, and feeding actually helps clear the infection, so there is no reason to discard the milk or stop nursing on that side.

Warm or cold compresses?

For the inflammation of mastitis, cold compresses are now generally preferred to reduce swelling and pain, especially after feeding. Brief warmth just before a feeding can help milk flow for some, but the emphasis has shifted to cold for the inflammation. Cool packs after nursing are a good default.

What is a breast abscess?

A collection of pus that can form if mastitis is not treated or does not clear. It feels like a firm, often fluctuant lump and usually needs draining, with a needle or a small procedure, alongside antibiotics.

How can I stop it coming back?

Address what caused it. Keep milk moving with regular, effective feeding, avoid skipped feedings and abrupt weaning, care for cracked nipples, and avoid pressure from tight bras. If your latch or supply is the issue, a lactation consultant can help enormously. Fixing the underlying cause is the best prevention.

When should I be worried?

Call your provider for a high fever with worsening pain, feeling very unwell, symptoms that do not improve or worsen after about 24 hours, a firm lump that persists, or red streaking from the area. These can mean you need antibiotics, a change in treatment, or drainage of an abscess.

Medically Reviewed · Updated

Reviewed by Dr. Grace Lin, MD, FACOG · OB-GYN

Obstetrician-gynecologist focused on reproductive and sexual health for women: pregnancy, BV, yeast, trichomoniasis and HPV/cervical screening. Our editorial guidelines →

6 Sources

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