Mastitis: Causes, Diagnosis, and Treatment


Mastitis is a bacterial infection in your breast. It almost always occurs when you start breastfeeding, usually during the first 6 to 12 weeks. During this time, it may be called lactation mastitis. Lactation mastitis affects about 10 percent of women who breastfeed. The infection can be treated, but one of the main problems is that a woman may stop breastfeeding.

Mastitis causes a sore breast and can make breastfeeding uncomfortable, but stopping is not advised. Emptying your breast of milk through breastfeeding helps treat mastitis. It is safe for your baby and it will help you recover quickly.

Causes and Risk Factors

The two main causes are a blocked milk duct and a sore or cracked nipple. If breast milk builds up in your breast, a duct may become blocked. Women who are just learning to breastfeed often do not completely empty their breasts. That’s why lactation mastitis tends to occur at the beginning of breastfeeding.

A sore nipple may develop a crack in the skin that allows bacteria from your skin or your baby’s mouth to get into your breast. Sore nipples are also more common in early breastfeeding. Other risk factors include:

  • Wearing a tight fitting bra
  • Being overtired, dehydrated, or poorly nourished
  • Not changing positions during breastfeeding or changing breasts before emptying
  • Waiting too long between feedings
  • Having a past history of mastitis
  • Having a baby that does not latch well
  • Having a baby with a cleft lip or palate
  • Having a pierced nipple

Symptoms and Diagnosis

The first symptom may be feeling like you are coming down with the flu. These symptoms may follow soon:

  • Breast pain and tenderness
  • Burning pain when breastfeeding
  • Redness, warmth, and swelling pointing toward the nipple
  • Chills and fever
  • Tiredness

You should let your doctor know about these symptoms right away. The main complication of mastitis is a collection of pus in the breast, called an abscess. Abscess is more likely if you stop breastfeeding, because milk stops flowing and bacteria can build up behind the blocked duct.

Your doctor can diagnose mastitis from your physical exam and symptoms. If your symptoms are severe or you do not respond to treatment quickly, your doctor may take a sample of breast milk to check for the type of bacteria. If your doctor suspects an abscess, an imaging study of your breast may be done using sound waves (breast ultrasound).


Treatment of lactation mastitis is to keep milk flowing and start an oral antibiotic. The most common bacteria to cause this infection are skin bacteria called Staphylococcus aureus. Your doctor will start an antibiotic that fights these bacteria. In most cases, you should start to feel better after two days.

It is important to keep breastfeeding if you can. Your doctor may suggest an over-the-counter pain medication. Using a warm compress or taking a hot shower before feeding may help breast milk flow more freely and less painfully. If you develop an abscess, your doctor may need to drain the pus with a needle or through a small surgical incision.

Lactation Mastitis Tips

 If you are having trouble breastfeeding, work with a lactation consultant.

  • Drink plenty of fluids, eat well, and get enough rest while breastfeeding.
  • Wear a supportive loose fitting bra.
  • Change positions while breastfeeding and make sure to empty one breast before switching to the other.
  • Avoid letting your breasts become full and swollen between feedings.
  • If you can’t breastfeed and your breasts are full, use a pump to empty your breasts.
  • If your doctor gives you an antibiotic for mastitis, make sure to take the full dose. Don’t stop if your breast feels better.
  • If you start an antibiotic and you are not getting better after two days, call your doctor.
Christopher Iliades
Dr. Chris Iliades is a medical doctor with 20 years of experience in clinical medicine and clinical research. Chris has been a full time medical writer and journalist since 2004. His byline appears in over 1,000 articles online including EverydayHealth, The Clinical Advisor, and Healthgrades. He has also written for print media including Cruising World Magazine, MD News, and The Johns Hopkins Children's Center Magazine. Chris lives with his wife and close to his three children and four grandchildren in the Boston area.

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