Mastitis is a condition in which the breast tissue becomes infected and is common in women who are breastfeeding. Mastitis occurs only rarely in pre- and post-menopausal women who have not just given birth.

What causes mastitis?

Bacteria entering the milk ducts through broken skin or a blocked milk duct can cause mastitis. This is why mastitis is most common in the first few weeks of breastfeeding when mother and baby are learning the skills necessary to breastfeed successfully.

A newborn needs feeding every few hours and this constant and sudden demand can be punishing on your nipples. Sore and cracked nipples provide an ideal route for bacteria living on the surface of the skin or from a baby’s mouth to enter the milk ducts.

Not fully emptying the milk from the breast or wearing a tight-fitting bra can block the milk ducts and cause mastitis.

Mastitis is also common in the early stages of weaning when mums are trying to cut down on breastfeeding.

Other conditions can lead to a breast infection, but do so much more rarely, and these include:

  • Hormonal changes
  • Smoking
  • Diabetes
  • Having a condition that weakens your immune system
  • Sometimes mastitis can develop after nipple piercing
  • Breast cancer: some types of breast cancers start in the lining of the milk duct, so an unexplained and sudden bout of mastitis in non-breastfeeding women can sometimes be a sign of a breast tumour

Mastitis symptoms

If you develop a breast infection you are likely to experience intense pain and swelling in the affected breast. The breast may feel hot, tender and lumpy to touch. Some women with mastitis may also have flu-like symptoms such as fever and chills and feel generally unwell. Mastitis rarely occurs in both breasts at the same time.

Diagnosing mastitis

A simple physical examination can help diagnose mastitis. If you are breastfeeding, your doctor may take a sample of breast milk for culture. This can help identify the type of bacteria causing the infection and determine the best course of treatment.

If you are not breastfeeding but develop mastitis then you may have the following tests:

  • Aspiration and culture. Breast fluid from the affected area is removed using a syringe and tested for bacteria
  • Ultrasound scan. This can help to look inside your breast and find out if a blocked milk duct is causing the breast infection
  • Mammogram. This is an X-ray of the breast and it can help identify early signs of breast cancer
  • Breast biopsy. A sample of cells or tissue is taken from the affected area to determine the type of cells and to rule out cancer

Is it safe to breastfeed if I have mastitis?

Breast milk from an infected breast is safe for your baby to drink.

Changing your breastfeeding technique and using a breast shield can help treat sore and cracked nipples. Placing a warm compress on the breast before and after a feed can help ease pain. If you can persevere with breastfeeding until the mastitis clears up, you can then go on to feed your baby for as long as you want.

Preventing mastitis

Women who are breastfeeding for the first time are most at risk of developing mastitis. If you are expecting a baby and plan to breastfeed, find out as much as you can about breastfeeding before your baby is born. The better prepared you are, the more confident you will feel when the time comes to put your baby on your breast.

Breastfeeding shouldn’t be painful, but newborn babies can sometimes find it difficult to latch on and if this happens you are more likely to have sore and cracked nipples.

A good breastfeeding technique can help your baby latch on properly and reduce the risk of damaging your nipples. You may need to try several different techniques before you find the one that suits you and your baby best. A good way of finding out if you are using the right technique is to ask your midwife to watch you put your baby on your breast.

While you are breastfeeding you can do plenty of things to reduce your risk of mastitis:

  • Express milk after a feed; young babies get easily tired so are unlikely to fully empty the milk from both breasts at each feed
  • Invest in a properly fitted nursing bra to support your breasts
  • Drink plenty of water to stop yourself getting dehydrated
  • Wash your hands often
  • Keep your nipples and the baby’s mouth clean

If you have sore and cracked nipples, wearing a nipple shield when breastfeeding can protect the nipple from further damage and can lessen your chance of developing mastitis.


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