Also known as breast infection

Mastitis is inflammation of the breast tissue, particularly the milk ducts and glands in a breastfeeding woman.

Mastitis is common, occurring in approximately 1 in 5 women. Half of these cases occur in the first 4 weeks of breastfeeding when cracked nipples, positioning problems and breast engorgement are most common.

There are two types of mastitis: non-infectious mastitis and infectious mastitis. 

Non-infectious mastitis

This type of mastitis is usually caused by breast milk staying within the breast tissue – milk stasis – because of a blocked milk duct or a breastfeeding problem. If left untreated, the milk left in the breast tissue can become infected, leading to infectious mastitis.

Infectious mastitis

This type of mastitis is caused by bacterial infection. It is important to receive treatment immediately to prevent complications, such as an abscess in the breast.


Milk stasis

When milk isn't completely emptied from a breast at feedings the milk left in the breast tissue can back up and become infected. This is known as milk stasis. Milk stasis may be caused by:

  • ineffective breast drainage caused by poor positioning and attachment
  • scheduled or restricted feeds, long gaps without feeding, missed or short feeds
  • sudden cessation of breastfeeding
  • over abundant milk supply
  • breast engorgement
  • blocked milk duct
  • pressure on a particular area of the breast caused by tight bra or holding the breast firmly during feeding
  • stress and fatigue which leads to less time for breastfeeding
  • separation from baby.

Bacteria entering your breast

Bacteria from your skin's surface and baby's mouth can enter the milk ducts through a break or crack in the skin of your nipple or through a milk duct opening. Bacteria can multiply, leading to infection. These germs aren't harmful to your baby – everyone has them. They just don't belong in your breast tissues.

Nipple damage may be caused by a baby not being being latched on correctly or having a tongue tie. In rare cases, untreated dermatitis of the nipple or surrounding area can be the cause. 

Risk factors for mastitis

  • past history of mastitis/abscess
  • local damage to breast
  • previous breast surgery.


While mastitis is common in the first month of breastfeeding, it can also occur at any stage when you are lactating and particularly when the number of breastfeeds or milk expressions is suddenly reduced.

Symptoms of mastitis include:

  • sore breast
  • lumpy area that is usually red and tender
  • fever
  • chills
  • feeling unwell with 'flu-like' symptoms.

Most cases of mastitis are caused because the baby is not latched on or positioned on the breast correctly leading to milk stasis, with blocked milk ducts and alveoli, and nipple trauma.


The key measures for managing mastitis are:

  • seek medical help
  • empty the breast
  • gentle massage
  • cold compresses after feeds
  • rest & pain relief.

See your doctor or midwife straight away if you have fever as you may require antibiotics to treat the infection.

  • Flucloxacillin 500mg four times per day (at least an hour before food), is the most commonly used antibiotic.
  • If you are allergic to penicillin, you must tell your doctor/midwife as a different antibiotic will be needed.

Self care

Empty the breast

  • Breastfeed on demand, starting with the sore breast. Make sure the baby is latched on correctly (mouth covering almost the entire areola - not just the nipple) and drains the breast well.
  • It is quite safe to feed your baby from the affected breast.
  • Try different feeding positions to improve drainage (baby's chin near the inflammed area).
  • Wear loose fitting clothes and a bra which is well fitting and does not 'dig in' anywhere (obstructing the flow of milk).
  • Change breast pads or bras frequently if you are 'leaking' milk.

Gentle massage and compresses

  • Warm compresses could be used to assist milk flow before feeding or expressing (e.g. a warm shower, or covered hot water bottle, or wrapped wheat bag). Make sure none of these are too hot.
  • "Gentle massage of the affected breast and lying flat prior to a feed can be helpful. The fingers (not tips) can be used in firm stroking movements towards the sternum and armpit. Care must be taken to avoid massage that is too firm as this can cause trauma and undue pressure and increase inflammation."
  • Cold packs can also be quite soothing when placed on the breast after feeding.
  • A soft stretchy support such as tubigrip or boob tube may be better than a bra at this time.

Rest and pain relief

  • It is very important that you have time to rest and spend time feeding your baby properly.
  • Ask your partner, family or whanau for more support so you can rest and recover.
  • If you do not have good support, ask your midwife or Plunket nurse to help you find some support.
  • Drink plenty of fluid (especially if you have a fever).
  • Paracetamol can be taken every four hours if necessary for the pain and fever.
  • Ibuprofen can also be helpful.
  • If not improving within 24 hours of treatment, seek further medical advice.
  • Sometimes antibiotics by a drip (IV) or other inpatient care is needed.


You can phone Plunketline on 0800 933 92 anytime day or night for advice about breastfeeding. You can also talk to your midwife, doctor or Plunket nurse

If you are still having breastfeeding problems, ask your midwife if you should be referred to a lactation consultant.

Other groups to contact include La Leche League NZ, your local Parents Centre NZ and Kellymom – an American lactation consultant website and Facebook Support Group.

Learn more 

Mastitis and breast abscesses Ministry of Health (NZ), 2014
Breastfeeding – wide range of resources  Ministry of Health (NZ), 2014 

Credits: Health Navigator team Sept 2014. Reviewed By: Andreea Dumitru, Senior RN from CCDHB, SIDU - Capital & Coast & Lower Hutt Last reviewed: 31 Oct 2015