Mastitis: Symptoms, What's Changed in Treatment, and What the Probiotic Research Says

By Melanie Nolan, BHSc Naturopathy, mum of four

It often starts with a sore spot you put down to a funny latch. By the afternoon there's a hot, red patch on one side, and by dinner you're shivering under a blanket, aching all over, with a baby who still needs feeding every two hours.

That's mastitis, and the speed of it catches a lot of women off guard. I've personally had mastitis over 30 times. So this is the guide I'd want you to have - what's actually happening in the breast, how the advice has changed, when to see your GP, and what the research on the breast milk microbiome is starting to show.

What mastitis actually is

For years we were taught a simple story: milk gets stuck, the duct blocks, the blockage gets infected. That model shaped the old advice too (massage the lump out, add heat, empty the breast).

In 2022 the Academy of Breastfeeding Medicine (ABM) revised its guidance in Clinical Protocol #36, The Mastitis Spectrum (Mitchell et al., 2022). It replaced the older mastitis and engorgement protocols and describes mastitis as a spectrum of conditions driven by inflammation in the ducts and swelling of the surrounding breast tissue, rather than a plug of milk.

The mastitis spectrum

• Ductal narrowing (what most of us still call a blocked duct). Inflamed, swollen tissue squeezes the milk ducts, so you get a tender, firm area but otherwise feel ok.
• Inflammatory mastitis. The inflammation spreads. The area becomes red or darker than the surrounding skin, hot and painful, and you may start to feel feverish and flu-ish.
• Bacterial mastitis. If inflammation doesn't settle, bacteria (commonly Staphylococcus species) can overgrow, and antibiotics may be needed.
• Abscess. A walled-off collection of pus that needs medical assessment, usually an ultrasound, and drainage.

The protocol also covers less common conditions such as phlegmon, galactocele and subacute mastitis. It isn't without critics, and some clinicians have questioned parts of its evidence base (Douglas, 2023), but the spectrum framing is now widely used.

Mastitis vs blocked duct

They sit on the same continuum. A blocked duct (ductal narrowing) is a localised tender lump and you feel well in yourself. Mastitis usually means redness and heat spreading across part of the breast, often with whole-body symptoms like fever, chills and aches.

Mastitis symptoms and red flags

Symptoms in the breast

• A tender, firm or wedge-shaped area
• Redness, which can be harder to see on darker skin and may look darker or purplish
• Heat and swelling
• Pain when feeding or expressing

Symptoms in your body

• Fever or chills
• Aches, exhaustion and that hit-by-a-truck, flu-like feeling

See your GP the same day if

• Your temperature is over 38°C
• You're not improving within 12-24 hours of starting comfort measures
• You feel very unwell
• A lump doesn't resolve, or feels fluid-filled or squishy (a possible abscess)
• Symptoms are getting worse on antibiotics, or both breasts are affected

Call 000 or go to emergency if

You have signs of sepsis: a racing heart or fast breathing, confusion or drowsiness, cold, clammy or mottled skin, or you feel extremely unwell. This is rare, but it's the reason the GP message above matters.

What's changed in mastitis management

If your mum, your friend or an old forum thread told you to massage it hard, pump until empty and use heat, that was standard advice for a long time. The ABM protocol moved away from it because those things can add to the inflammation and tissue damage that drives mastitis in the first place.

Here's the current approach, which your GP, midwife or IBCLC will tailor to you:

• Gentle lymphatic drainage, not deep massage. Very light, skin-stretching strokes from the breast towards the lymph nodes in your armpit. If it hurts, it's too firm.
• Cold, not heat. A cold pack or ice wrapped in a cloth between feeds helps reduce swelling.
• Anti-inflammatory pain relief. Your GP or pharmacist can advise on options considered compatible with breastfeeding, such as ibuprofen and paracetamol, and the right dose for you.
• Feed to comfort, not to empty. Keep feeding your baby as usual. Pumping extra to "drain" the breast tells your body to make more milk, which can feed the cycle.
• Avoid oversupply. If you've been pumping a lot to build a stash, talk to an IBCLC about bringing it back gradually.
• Support and rest. A well-fitted, non-restrictive bra, and as much lying down as your life allows (I know).

If your GP diagnoses bacterial mastitis, antibiotics may be needed. Please take the full course as prescribed.

Risk factors, and can you prevent mastitis?

You can't control every factor, but these are the ones worth knowing:

• Latch and positioning. A shallow latch can damage nipples and affect how milk moves. An IBCLC can help early.
• Oversupply. Often driven by pumping beyond what your baby needs.
• Pressure on the breast. Tight or underwire bras, baby carrier and bag straps, or sleeping on your stomach.
• Missed or rushed feeds and sudden changes. Baby sleeping a longer stretch, returning to work, or weaning quickly.
• Nipple damage. Cracks and grazes add inflammation and give bacteria a way in.
• Fatigue and stress. Being run down matters more than we give it credit for.
• Previous mastitis. Having it once makes you more likely to have it again.

The breast milk microbiome and mastitis

This is the part I find most interesting as a naturopath, and it's where the research has moved a lot in the past fifteen years.

Breast milk isn't sterile. It has its own community of bacteria, the milk microbiota, that helps seed your baby's gut (Fernández et al., 2013). One hypothesis is that some of these bacteria travel from the mother's gut to the breast, the so-called entero-mammary pathway (Rodríguez, 2014).

In the ABM model, mastitis is linked with mammary dysbiosis: a shift in that community where bacteria such as Staphylococcus overgrow and can form biofilms that narrow the ducts further. Which raises the obvious research question - can supporting the bacterial balance help?

What the probiotic research shows

A note on names first: several Lactobacillus species were reclassified in 2020, so L. fermentum is now Limosilactobacillus fermentum and L. salivarius is now Ligilactobacillus salivarius. The older papers use the old names.

• Arroyo et al., 2010. 352 breastfeeding women with bacterial mastitis took L. fermentum CECT5716, L. salivarius CECT5713, or the antibiotics prescribed by their own doctor for 21 days. The probiotic groups had greater reductions in breast pain and milk bacterial counts, and lower recurrence.
• Hurtado et al., 2017. In a double-blind, placebo-controlled trial of 625 breastfeeding women, taking L. fermentum CECT5716 daily for 16 weeks was associated with a 51% lower incidence of clinical mastitis compared with placebo.
• Fernández et al., 2016. 108 pregnant women who'd had mastitis after a previous birth took L. salivarius PS2 or placebo from around 30 weeks. Mastitis occurred in 25% of the probiotic group and 57% of the placebo group.
• Cochrane review, 2020. Pooling the trials, the reviewers concluded probiotics may reduce the risk of mastitis compared with placebo, but rated the evidence as low certainty (Crepinsek et al., 2020).

Mum and baby are one system

The idea I keep coming back to is the mother-baby dyad. Your microbiome helps shape your milk, your milk helps shape your baby's gut, and your baby's mouth is in contact with your breast many times a day. It's a shared system, and supporting your own microbiome during breastfeeding is part of looking after both of you.

Where MotherBloom fits

MotherBloom is our four-strain probiotic for pregnancy and breastfeeding. I formulated it around strains researched in pregnant and breastfeeding women, with the strain codes and the CFU of each strain listed so you and your practitioner can look them up.

While you're breastfeeding, MotherBloom helps relieve symptoms of mild mastitis and helps reduce the occurrence of symptoms of mild mastitis. It isn't a replacement for seeing your GP, and it doesn't replace antibiotics if you need them. If you have a fever, a hot red area on your breast or you feel unwell, please see your GP the same day.

When to get help

You don't have to work this out alone, and you don't need to wait until it's bad:

• Your GP for assessment, fever, or anything on the red flag list above
• An IBCLC (lactation consultant) for latch, positioning and supply - you can find one through Lactation Consultants of Australia and New Zealand
• Your midwife or maternal child health nurse
• The Australian Breastfeeding Association Breastfeeding Helpline: 1800 686 268, available 24/7

Mastitis FAQs

Can I keep breastfeeding with mastitis?

Yes. Continuing to feed is recommended and is safe for your baby. Feed as you normally would, to comfort. If one side is too painful, gently express just enough to stay comfortable.

Is my breast milk safe for my baby if I have mastitis?

Yes. Your milk may taste a little saltier and your baby might fuss on that side, and supply on that side can dip temporarily. If you need antibiotics, your GP will choose one compatible with breastfeeding.

Should I use heat or cold for mastitis?

Cold. A cold pack wrapped in a cloth between feeds helps reduce swelling. Current guidance moved away from heat because it can increase inflammation.

How long does mastitis last?

Inflammatory mastitis often improves within a day or two of gentle care. If you're not improving within 12-24 hours, or you have a fever, see your GP. If you're prescribed antibiotics, most women feel noticeably better within about 48 hours.

Can mastitis come back?

Yes, recurrence is common. It's worth looking at the underlying drivers with an IBCLC, such as latch, oversupply or pressure. If it keeps coming back in the same spot, your GP may suggest an ultrasound.

What's the difference between a blocked duct and mastitis?

They're on the same spectrum. A blocked duct is a localised tender lump and you otherwise feel well. Mastitis usually involves spreading redness and heat, and often fever and flu-like symptoms.

Do probiotics help with mastitis?

Some specific strains have been studied for mastitis, with promising results in several trials. A 2020 Cochrane review found probiotics may reduce the risk of mastitis. Effects are strain-specific, MotherBloom has been designed for mastitis. 

This article is general information only and isn't a substitute for advice from your doctor or healthcare professional. If you have symptoms of mastitis, please see your GP.

Looking after your microbiome while you're breastfeeding? Shop MotherBloom. 

Always read the label and follow the directions for use.

References

1. Mitchell KB, Johnson HM, Rodríguez JM, Eglash A, Scherzinger C, Zakarija-Grkovic I, Cash KW, Berens P, Miller B; Academy of Breastfeeding Medicine. Academy of Breastfeeding Medicine Clinical Protocol #36: The Mastitis Spectrum, Revised 2022. Breastfeed Med. 2022;17(5):360–376. doi:10.1089/bfm.2022.29207.kbm
2. Douglas P. Does the Academy of Breastfeeding Medicine's Clinical Protocol #36 'The Mastitis Spectrum' promote overtreatment and risk worsened outcomes for breastfeeding families? Commentary. Int Breastfeed J. 2023;18(1):51. doi:10.1186/s13006-023-00588-8
3. Arroyo R, Martín V, Maldonado A, Jiménez E, Fernández L, Rodríguez JM. Treatment of infectious mastitis during lactation: antibiotics versus oral administration of lactobacilli isolated from breast milk. Clin Infect Dis. 2010;50(12):1551–1558. doi:10.1086/652763
4. Hurtado JA, Maldonado-Lobón JA, Díaz-Ropero MP, et al. Oral administration to nursing women of Lactobacillus fermentum CECT5716 prevents lactational mastitis development: a randomized controlled trial. Breastfeed Med. 2017;12(4):202–209. doi:10.1089/bfm.2016.0173
5. Fernández L, Cárdenas N, Arroyo R, Manzano S, Jiménez E, Martín V, Rodríguez JM. Prevention of infectious mastitis by oral administration of Lactobacillus salivarius PS2 during late pregnancy. Clin Infect Dis. 2016;62(5):568–573. doi:10.1093/cid/civ974
6. Crepinsek MA, Taylor EA, Michener K, Stewart F. Interventions for preventing mastitis after childbirth. Cochrane Database Syst Rev. 2020;9:CD007239. doi:10.1002/14651858.CD007239.pub4
7. Fernández L, Langa S, Martín V, et al. The human milk microbiota: origin and potential roles in health and disease. Pharmacol Res. 2013;69(1):1–10. doi:10.1016/j.phrs.2012.09.001
8. Rodríguez JM. The origin of human milk bacteria: is there a bacterial entero-mammary pathway during late pregnancy and lactation? Adv Nutr. 2014;5(6):779–784. doi:10.3945/an.114.007229
9. Zheng J, Wittouck S, Salvetti E, et al. A taxonomic note on the genus Lactobacillus: description of 23 novel genera. Int J Syst Evol Microbiol. 2020;70(4):2782–2858. doi:10.1099/ijsem.0.004107