Mastitis: Symptoms, Causes, and Treatment
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD. Last reviewed October 17, 2026. This content is for educational purposes and is not medical advice.
Quick Answer: What is mastitis?
Mastitis is inflammation of breast tissue that sometimes involves an infection, most often in people who are breastfeeding. Symptoms include breast tenderness, warmth, swelling, redness, a lump and a fever of 101 F (38.3 C) or greater. It is treated with a 10-day course of antibiotics when infection is present, pain relievers and continued breastfeeding or milk expression.
What the research says
Based on abstracts retrieved from PubMed:
Poor milk removal and technique drive the risk. A meta-analysis of 14 studies (8,032 participants) in China found that significant risk factors for lactation mastitis included improper milking method (OR 6.79, 95% CI 3.45 to 13.34), repeated milk stasis (OR 6.23, 95% CI 4.17 to 9.30), the first six months postpartum (OR 5.11, 95% CI 2.66 to 9.82), crater or abnormal nipple (OR 3.94, 95% CI 2.34 to 6.63), and improper breastfeeding posture (OR 2.47, 95% CI 2.09 to 2.92) (Lai et al., PLoS One, 2021).
Nipple damage, blocked ducts, and prior mastitis matter. A meta-analysis of 8 cohort and 10 case-control studies identified previous mastitis during breastfeeding, breast trauma, a blocked duct, a cracked nipple, and latch problems within 8 weeks after delivery as significant risk factors. Washing the nipples before breastfeeding was linked to lower risk (Deng et al., West J Nurs Res, 2021).
Evidence on prevention is still limited. A Cochrane review of 10 trials (3,034 women) found that probiotics may reduce the risk of mastitis compared with placebo (RR 0.51, 95% CI 0.35 to 0.75; 2 trials, 399 women), but this was low-certainty evidence, and the review noted that the evidence is incomplete (Crepinsek et al., Cochrane Database Syst Rev, 2020).
Key Facts at a Glance
Key fact | What it means |
What it is | Inflammation of breast tissue, sometimes with infection [1] |
Who gets it | Most often people who are breastfeeding; can affect others [1] |
Onset | Symptoms can appear suddenly, in one or both breasts [1] |
Contagious | Not contagious; safe to keep breastfeeding even on antibiotics [2] |
Main complication | An abscess (pus collection) that may need surgical draining [1] |
What exactly is the condition called mastitis?
Mastitis is swelling and redness, called inflammation, of breast tissue. It sometimes involves an infection. Besides causing swelling and redness, mastitis causes breast pain and warmth. An infection can also cause fever and chills [1].
Mastitis most often affects people who are breastfeeding, where it is called lactation mastitis. But mastitis can also happen to people who aren't breastfeeding [1].
Lactation mastitis can leave you feeling run down, making it hard to care for your baby. It sometimes leads people to wean earlier than they planned. The good news is that continuing to breastfeed is better for you and your baby, even if you're taking an antibiotic [1].
What are the warning signs and symptoms of mastitis?
Symptoms of mastitis can appear suddenly. They may show up in one or both breasts. They may include breast tenderness or warmth, breast swelling, thickening of breast tissue or a breast lump, pain or a burning feeling all the time or while breastfeeding, skin redness that is often in a wedge-shaped pattern, feeling ill, and a fever of 101 degrees Fahrenheit (38.3 degrees Celsius) or greater [1].
Warning sign | What you might notice |
Tenderness and warmth | The breast feels sore, warm, or hot to the touch [1] |
Swelling | The breast looks or feels swollen [1] |
Lump or thickening | Breast tissue thickens or forms a lump [1] |
Pain or burning | Constant pain or a burning feeling, especially during breastfeeding [1] |
Redness | Skin redness, often in a wedge-shaped pattern; may be harder to see on Black or brown skin [1] |
Feeling ill | You feel generally unwell, achy, or run down [1] |
Fever and chills | Fever of 101 F (38.3 C) or greater, sometimes with chills [1] |
Keep in mind that skin redness can be harder to see on Black or brown skin. Look for warmth, swelling, tenderness, and how you feel overall, not just color change [1].
When to See a Doctor
See your healthcare professional if you have breast symptoms that worry you. This is especially important because untreated mastitis can develop into a more serious problem [1].
What causes mastitis to develop?
The main cause of mastitis is milk that is trapped in the breast [1].
A blocked milk duct. If a breast doesn't empty all the way during feedings, one of the milk ducts can get clogged. Milk then backs up, which can lead to a breast infection [1].
Germs entering the breast. Germs from the skin's surface and from a baby's mouth can enter the milk ducts. This can happen through a crack in the skin of the nipple or through a milk duct opening. Germs grow in milk that stays in a breast that isn't emptied [1].
To understand how this works, it helps to picture the breast's structure. Each breast has sections called lobules that branch out from the nipple. Each lobule holds tiny hollow sacs, and these lobules are linked by a network of thin tubes called ducts. When you breastfeed, ducts carry milk toward the nipple [1].
What are the risk factors for mastitis?
A number of risk factors can make mastitis more likely to develop. Most relate to milk drainage, nipple skin, or overall fatigue and health [1].
Risk factor | How it raises risk |
History of mastitis | Having had mastitis before makes it more likely again [1] |
Sore or cracked nipples | Cracks give germs a way into the milk ducts [1] |
Pressure on the breast | A tight bra or tight seat belt can restrict milk flow [1] |
Not nursing correctly | A poor latch or uneven drainage leaves milk behind [1] |
Overtired or stressed | Being overly tired or stressed lowers your defenses [1] |
Eating poorly | Poor nutrition can work against recovery [1] |
Smoking | Smoking raises the risk of mastitis [1] |
What complications can mastitis cause?
Mastitis that isn't treated, or mastitis caused by a blocked duct, can cause pus to build up in the breast. This is called an abscess. An abscess most often needs to be drained surgically [1].
To avoid this complication, talk with your healthcare professional as soon as you get symptoms of mastitis. You may need to take a course of antibiotics [1].
How can you prevent mastitis?
If you're planning to breastfeed, think about meeting with a breastfeeding specialist, called a lactation consultant, before you start. This can help you avoid complications such as mastitis [1].
You can also lower your chances of getting mastitis day to day. Feeding your baby on demand, or letting out milk with your hand (called expressing) often, helps keep milk moving. Fully draining the milk from your breasts while breastfeeding matters too [1].
Prevention step | What to do |
Feed on demand | Breastfeed when your baby is hungry, or express milk often by hand [1] |
Drain fully | Fully drain the milk from your breasts while breastfeeding [1] |
Finish one breast first | Let your baby empty one breast all the way before switching to the other [1] |
Switch positions | Change the breastfeeding position from one feeding to the next [1] |
Good latch | Make sure your baby latches on well during feedings [1] |
If you smoke | Talk with your healthcare professional about how to quit [1] |
How is mastitis diagnosed?
Your healthcare professional starts with a physical exam and questions about your symptoms and medical history. You might have a breast ultrasound. Your clinician might also take out, or aspirate, some of the fluid in your breast. A culture of this fluid can help find the best antibiotic for you [2].
There is one important look-alike. A rare form of breast cancer, called inflammatory breast cancer, can cause redness and swelling that might be confused with mastitis. Because of this, your healthcare professional may suggest a mammogram or an ultrasound or both [2].
If your symptoms don't go away after you take a full course of antibiotics, you may need a biopsy to make sure you don't have breast cancer. That's why following up with your healthcare professional after you've taken all the antibiotics matters [2].
Diagnostic step | What it does |
Physical exam | Clinician checks the breast and reviews symptoms and history [2] |
Breast ultrasound | Imaging that looks inside the breast tissue [2] |
Fluid aspiration and culture | A sample of breast fluid is drawn and cultured to find the best antibiotic [2] |
Mammogram or ultrasound | Ordered when a rare cancer could be confused with mastitis [2] |
Biopsy | Done if symptoms persist after a full course of antibiotics, to rule out breast cancer [2] |
What are the treatment options for mastitis?
Mastitis treatment might involve antibiotics, pain relievers, and ways to keep milk draining. The reassuring point: it is safe to keep breastfeeding if you have mastitis. Breastfeeding helps clear the infection. Weaning your baby suddenly might actually make your symptoms worse [2].
Antibiotics
If you have an infection, a 10-day course of antibiotics is most often needed. Take all the medicine. This lowers the risk of the infection coming back. If your mastitis doesn't clear up after taking antibiotics, contact your healthcare professional [2].
Pain Relievers
You can try a medicine available without a prescription, such as acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin IB, others) [2].
Breastfeeding Support
You might see a specialist in breastfeeding, called a lactation consultant, for help and support. Advice on the best way to breastfeed might include the following steps [2].
Don't let your breasts fill too much between feedings. Try to get your infant to latch on well, which can be hard when your breast is swollen. Letting out a small amount of milk by hand before breastfeeding, called expressing, might help [2].
Lightly massage the breast while breastfeeding or pumping milk. Start at the affected area and move down toward the nipple. Do not press hard or squeeze [2].
Make sure your breast drains all the way during breastfeeding. If you have trouble emptying your breast, put a warm, moist cloth on the breast before breastfeeding or pumping milk. Breastfeed on the affected side first, when your infant is hungrier and sucking harder. Change your breastfeeding positions, and drink plenty of fluids [2].
Breastfeeding step | Why it helps |
Express before feeding | A small amount of milk by hand can soften the breast and help the baby latch [2] |
Light massage | Start at the affected area and move toward the nipple; do not press hard or squeeze [2] |
Warm moist cloth first | Helps the breast drain fully if emptying is hard [2] |
Feed on affected side first | Your baby is hungrier and sucking harder at the start [2] |
Change positions | Different positions help drain different areas of the breast [2] |
Drink fluids | Supports milk production and recovery [2] |
Lifestyle and Home Remedies
To help yourself feel better, don't let your breasts fill up with too much milk between breastfeeding sessions. Put a cool cloth or ice pack on your breast after breastfeeding. Wear a bra that supports your breasts, and rest as much as you can [2].
How should you prepare for a mastitis appointment?
You may be sent to an obstetrician-gynecologist. For problems related to breastfeeding, you may be referred to a lactation consultant [2].
Before the visit, make a list of your symptoms, including any that may not seem linked to the reason for the appointment and when they began. List all medicines, vitamins, and supplements you take, including doses, plus key medical information and the questions you want to ask [2].
Useful questions to ask include: Will my mastitis clear on its own or do I need treatment? What can I do at home to relieve my symptoms? How might my condition affect my baby? If I keep breastfeeding, is the medicine you're prescribing safe for my baby? How long will I have to take the medicine? What are the chances the infection will come back, and how do I lower my risk? [2]
Your healthcare professional might ask you: Are your symptoms in one or both breasts? How bad is your pain? How do you breastfeed? Have you had mastitis before? [2]
Conclusion and Next Steps
Mastitis is common, uncomfortable, and very treatable. It starts when milk stays trapped in the breast or germs get in, and it announces itself with sudden swelling, warmth, pain, and sometimes fever. The core treatment is straightforward: antibiotics when an infection is present, pain relief, rest, and, most importantly, keeping the milk draining by continuing to breastfeed.
See a healthcare professional early rather than waiting it out. Prompt treatment clears the infection, protects your breastfeeding relationship, and prevents the main complication, an abscess that may need surgery.
Take action: If you develop breast pain, warmth, redness, or a fever of 101 F (38.3 C) or greater, contact your healthcare professional right away and finish every day of any prescribed antibiotic. Keep breastfeeding or expressing milk on the affected side, rest, and follow up if symptoms don't clear.
Frequently Asked Questions
What are the first signs of mastitis?
The first signs usually appear suddenly in one or both breasts and include tenderness, warmth, swelling, tissue thickening or a lump, pain or burning while breastfeeding, skin redness often in a wedge shape, feeling ill, and a fever of 101 F (38.3 C) or greater. Redness may be harder to see on Black or brown skin, so warmth and swelling matter just as much.
What causes mastitis in breastfeeding women?
The main cause is milk trapped in the breast. A blocked milk duct, when the breast doesn't empty during feedings, lets milk back up, and germs from the skin or baby's mouth can enter through a nipple crack and grow in the trapped milk.
Can I keep breastfeeding with mastitis?
Yes. It is safe to keep breastfeeding with mastitis, and breastfeeding actually helps clear the infection. Weaning suddenly might make symptoms worse. It is also safe to breastfeed while taking a prescribed antibiotic.
How is mastitis treated?
Treatment most often involves a 10-day course of antibiotics, which you should finish completely, plus over-the-counter pain relievers such as acetaminophen or ibuprofen. Continued breastfeeding or milk expression, warm compresses, gentle massage, good positioning, and rest help the breast drain and speed recovery.
When should I go back to the doctor after treatment?
Follow up after finishing all your antibiotics. If your symptoms don't go away, you may need a breast ultrasound, a fluid culture, or even a biopsy, because a rare breast cancer can look like mastitis and must be ruled out.
Trusted External Resources
Mayo Clinic: Mastitis: Symptoms and causes
Mayo Clinic: Mastitis: Diagnosis and treatment
Related Reading
Nipple Shields: When and How to Use Them explains when nipple shields help with breastfeeding.
Clinical Breast Exam (CBE): What to Expect, How Often and What Results Mean explains the hands-on breast check that can find lumps and other changes.
References
Mayo Clinic Staff. Mastitis - Symptoms and causes. Mayo Clinic. August 13, 2024. https://www.mayoclinic.org/diseases-conditions/mastitis/symptoms-causes/syc-20374829
Mayo Clinic Staff. Mastitis - Diagnosis and treatment. Mayo Clinic. August 13, 2024. https://www.mayoclinic.org/diseases-conditions/mastitis/diagnosis-treatment/drc-20374834
Lai BY, Yu BW, Chu AJ, et al. Risk factors for lactation mastitis in China: A systematic review and meta-analysis. PLoS One. 2021;16(5):e0251182. PMID 33983987. https://doi.org/10.1371/journal.pone.0251182
Deng Y, Huang Y, Ning P, Ma SG, He PY, Wang Y. Maternal Risk Factors for Lactation Mastitis: A Meta-analysis. West J Nurs Res. 2021;43(7):698-708. PMID 33089754. https://doi.org/10.1177/0193945920967674
Crepinsek MA, Taylor EA, Michener K, Stewart F. Interventions for preventing mastitis after childbirth. Cochrane Database Syst Rev. 2020;9(9):CD007239. PMID 32987448. https://doi.org/10.1002/14651858.CD007239.pub4
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