Mastitis is a painful complication of breastfeeding.  It is defined as inflammation of the mammary gland, which causes the breast to become painful, swollen, and red.  

It is most common in the first three months of breastfeeding, but it can occur at any time.  

What Causes Mastitis?

Mastitis is usually caused by poor milk drainage, like a plugged duct.  Some causes for mastitis include:

  • Plugged milk ducts
  • Engorgement
  • Poor feeding technique
  • Nipple trauma
  • Milk oversupply
  • Abrupt changes in feeding or weaning

If issues causing poor milk drainage persist longer than 24 hours, you are at risk of developing mastitis. Breast milk contains bacteria.  This is why inadequate drainage of milk can cause mastitis.  The most common bacteria that cause mastitis are Staphylococcus aureus (S.aureus).  

What Are The Symptoms of Mastitis?

In addition to the breast being painful, swollen and firm, and red, you may also experience a fever and flu-like symptoms.  This may be muscle aches, chills, and fatigue.  Mastitis usually only occurs on one side.  

Treatment of Mastitis

Once mastitis is diagnosed, antibiotics are required to treat the infection.  Your health care provider will prescribe the most appropriate antibiotic for you.  

Continue breastfeeding on demand and ensure drainage of the affected breast.  Nursing frequently will help reduce inflammation, provide comfort and open the milk blockage.  Milk from the affected breast is not harmful to the baby.  Ibuprofen may be helpful for pain and inflammation caused by mastitis.  Cold compresses may ease the discomfort between feedings. 

It may be helpful to see a lactation consultant to assess breastfeeding technique.  

Get as much rest as possible, and drink plenty of fluids. 

This post was co-authored by Erin Manchuk, BScPharm, BCGP and Stephanie Liu, MD, MSc, CCFP, BHSc.