Breast Infection: Symptoms, Causes and Treatment

Quick answer

Mastitis is inflammation of the breast, usually during breastfeeding, causing a red, hot, painful area with flu-like symptoms. It is not always a bacterial infection, and many cases settle with supportive care. Keep breastfeeding, use cold rather than heat, avoid deep massage, and contact your doctor if you are not improving within 24 hours or feel very unwell.

Key takeaways

• Keep breastfeeding. Your milk is safe for your baby, and stopping increases the risk of an abscess.

• Cold, not heat. Current guidance favours cold to reduce swelling. Prolonged heat increases inflammation in already swollen tissue.

• Avoid deep massage and extra pumping. Both were standard advice for years and both are now understood to make things worse.

• Not every case needs antibiotics. Many begin as inflammation rather than infection and settle with supportive care.

• A red, swollen breast that does not respond to treatment within about two weeks needs imaging, because inflammatory breast cancer can look exactly like mastitis.

What is mastitis?

Inflammation of breast tissue, most commonly in breastfeeding women, though it can occur outside breastfeeding too.

The current understanding is that mastitis is a spectrum rather than a single condition, and where you sit on it determines the treatment.

This matters practically. Treating every case as a bacterial infection leads to unnecessary antibiotics, and treating every case with massage and heat makes the swelling worse.

Symptoms

Onset is usually rapid. Many women feel fine in the morning and unwell by evening.

What causes it

• Milk not being removed effectively, most often because of a shallow latch or an ineffective feed

• Long gaps between feeds, or a sudden change in feeding pattern

• Oversupply, which makes ineffective drainage more likely

• Pressure on the breast, from a tight or badly fitting bra, an underwire, a bag strap, a baby carrier, a seatbelt or a sleeping position

• Cracked or damaged nipples, which let bacteria in

• Abrupt weaning

• Being run down, with poor sleep and high demand

• A tongue-tie in the baby, causing ineffective milk transfer

Recurrence in the same spot usually has a structural cause. Latch, oversupply, tongue-tie or steady pressure from something you wear. Treating each episode without finding the cause means it keeps happening.

What to do: the treatment that current guidance supports

This section has changed substantially, and much of the advice still circulating now runs against it.

What to actually do

1. Keep feeding as normal. Start on the affected side if comfortable. If too painful, start on the other side and switch once let-down begins

2. Apply cold between feeds, 15 minutes at a time, wrapped in a cloth

3. Take an anti-inflammatory if appropriate. Ibuprofen reduces both pain and inflammation and is generally considered compatible with breastfeeding. Paracetamol can be added. Confirm with your doctor

4. Very light lymphatic drainage only, using the pressure you would use on a closed eyelid

5. Rest and drink fluids. This is a systemic illness and rest genuinely helps

6. Wear a supportive, non-compressive bra. No underwire while symptomatic

7. Get the latch checked if this is not your first episode

Set a 24-hour checkpoint. If you have a fever and are not improving within about 24 hours, or you are getting worse at any point, contact your doctor.

When antibiotics are needed

Not every case needs them, which is a change from how mastitis was managed for decades.

Antibiotics are usually prescribed if:

• You are significantly unwell, with a high fever, rigors or a rapid pulse

• You are not improving within about 24 hours of supportive care

• You have a cracked or infected nipple as an obvious entry point

• Symptoms are worsening rather than settling

• You are immunocompromised, or have another condition that raises risk

If you are prescribed them:

• Complete the full course, even once you feel better

• Most antibiotics used for mastitis are compatible with breastfeeding. Tell your doctor you are feeding

• Keep feeding throughout

• If you are not improving after 48 hours on antibiotics, go back. That usually means either the wrong antibiotic or an abscess forming

Breast abscess

A collection of pus that develops when infection is not controlled. It feels like a firm, very tender swelling that may feel fluid-filled, and symptoms usually worsen despite antibiotics.

How it is diagnosed: an ultrasound, which confirms whether a collection is present and how large.

How it is treated:

• Ultrasound-guided needle aspiration is now the preferred first approach for most abscesses. A needle draws out the pus, sometimes over more than one session. It is less invasive, heals faster, and usually leaves little or no scar

• Surgical incision and drainage is reserved for larger abscesses, those with multiple compartments, or those that do not settle with aspiration

• Antibiotics alongside

• You can usually continue breastfeeding, including from the affected breast in most cases. Your doctor will advise if the drainage site makes that difficult, in which case expressing from that side keeps supply going

An abscess does not mean you have to stop feeding.

The red flag that is not an infection

A red, swollen breast that does not settle with treatment needs imaging, because inflammatory breast cancer can present exactly like mastitis.

Features that should raise concern:

• Not improving after about two weeks of appropriate treatment, including antibiotics

• No fever, despite a dramatically red and swollen breast

• Skin that looks thickened, dimpled or pitted, like orange peel

• The redness covering a large part or all of the breast, rather than one wedge

• A newly inverted or retracted nipple

• A firm lump that remains after the redness and pain have gone

• Occurring in a woman who is not breastfeeding

This is uncommon, and most red painful breasts are mastitis. But inflammatory breast cancer is frequently treated as mastitis for weeks before it is recognised, and the delay matters. Any mastitis that has not resolved within two weeks should be imaged, and any lump that persists after the inflammation settles should be examined.

Our guide to breast cancer signs and screening covers the wider picture.

Breast infection when you are not breastfeeding

The heading on most articles says breast infection, and then only covers breastfeeding. Infections do occur outside lactation.

Any breast infection in a woman who is not breastfeeding should be assessed properly, including imaging, because the differential is wider and includes cancer.

Preventing recurrence

• Get the latch assessed. The most common fixable cause

• Feed on demand, avoiding long unplanned gaps

• Do not pump "just in case." Pumping beyond your baby's needs builds oversupply

• Check what presses on your breast: bra underwire, bag strap, carrier, seatbelt, sleeping position

• Treat cracked nipples early

• Get a tongue-tie assessed if feeds are painful or long

• Wean gradually. Abrupt weaning is a common trigger

• If you smoke, stopping matters, particularly for periductal mastitis

Three or more episodes deserves proper investigation, not another course of antibiotics.

When to see a doctor

Seek care the same day if you have:

• Fever with breast pain that is not improving within 24 hours, or a temperature above 38.5°C

• Feeling very unwell, with severe chills, a racing heart, confusion, or unable to keep fluids down

• Spreading redness across the breast

• A swollen, very tender lump worsening despite antibiotics

• Pus draining from the nipple or breast

• Red streaking spreading towards the armpit

Book an appointment for:

• A lump remaining after the pain and redness have settled

• Mastitis not resolving within two weeks

• Repeated episodes, three or more

• Skin dimpling, an orange-peel texture, or a newly inverted nipple

• Any breast infection when you are not breastfeeding

• Bloody nipple discharge

Frequently asked questions

Can I keep breastfeeding with mastitis?
Yes, and you should. Your milk is safe for your baby, and continuing helps resolve it. Stopping increases the risk of an abscess.

Should I use a hot or cold compress?
Cold, for swelling and pain between feeds. Brief warmth immediately before a feed can help let-down, but avoid prolonged heat.

Should I massage the lump?
No. Deep massage worsens inflammation and can bruise the tissue. Only very light strokes towards the armpit.

Should I pump extra?
No. Feed your baby normally. Extra pumping increases supply and worsens the cycle.

Does mastitis always need antibiotics?
No. Many cases start as inflammation rather than bacterial infection and settle with supportive care. Antibiotics are needed if you are significantly unwell or not improving within about 24 hours.

How long does mastitis take to clear?
Improvement usually begins within 24 to 48 hours with appropriate treatment. Anything not settling within two weeks needs imaging.

What does a breast abscess feel like?
A firm, very tender swelling that may feel fluid-filled, usually with symptoms worsening despite antibiotics. It is diagnosed on ultrasound.

Will I need surgery for an abscess?
Usually not. Ultrasound-guided needle aspiration is the preferred first approach for most abscesses, with surgery reserved for larger or more complex ones.

Can you get mastitis without breastfeeding?
Yes. Periductal mastitis, granulomatous mastitis and infected cysts all occur outside lactation, and any of them should be properly assessed.

When should I worry it is not an infection?
If a red, swollen breast has not settled within about two weeks of appropriate treatment, if there is no fever despite dramatic redness, or if the skin looks dimpled or like orange peel. These need imaging.

The bottom line

Mastitis is inflammation before it is infection, which is why many cases settle without antibiotics and why the old advice to massage hard, apply heat and pump more has been replaced by cold, gentle handling and normal feeding. Keep breastfeeding, set yourself a 24-hour checkpoint, and go back if antibiotics are not working within 48 hours. And hold on to one rule above the rest: a red, swollen breast that has not resolved in two weeks needs a scan, because that is the presentation most often mistaken for an infection when it is something else.

Sources

• Academy of Breastfeeding Medicine, Clinical Protocol #36: The Mastitis Spectrum

• NHS, mastitis and breast abscess

• World Health Organization, mastitis: causes and management

• American College of Obstetricians and Gynecologists, breastfeeding challenges

• National Institute for Health and Care Excellence, mastitis and breast abscess

• National Institutes of Health, LactMed, Drugs and Lactation Database

• Peer-reviewed literature on ultrasound-guided aspiration of breast abscess and on inflammatory breast cancer presentation

This article is for general information and is not a substitute for professional medical advice. Seek care the same day for fever that is not improving in 24 hours, spreading redness, or feeling very unwell. See a doctor for any red breast that has not resolved within two weeks.