Is it Thrush or Subclinical Mastitis?

Subclinical or subacute mastitis should be included in a differential diagnosis* of nipple thrush. The presenting symptoms for both of these conditions are similar, but there are a couple of distinct differences:

  1. Thrush will generally always be bilateral, while subclinical mastitis will usually be unilateral.
  2. The breast pain associated with thrush happens after or between breastfeeds. Breast pain caused by subclinical mastitis is usually most intense when a mother has a milk ejection reflex (MER) at the beginning of a feed.

Subclinical mastitis is caused by an overgrowth of the normal bacteria (staph and strep) that inhabit the breast and form thin biofilms around the milk ducts. They do not produce the toxins that can lead to acute mastitis, but they can form thick biofilms around the ducts, inflaming the epithelium and narrowing the ducts. This makes it more difficult for milk to pass through, and the pain felt on MER can be felt as a stabbing, crampy or burning sensation.

These symptoms are often misdiagnosed as thrush. Women are then prescribed Diflucan, which does little to resolve the pain they are experiencing and appropriate treatment is delayed. In my private practice work, I have seen several cases like this; in one instance a client had been taking Diflucan and using thrush creams on and off for a two month period. I referred her back to her GP and suggested doing swabs of her nipples. The swabs revealed Methicillin-sensitive Staphylococcus Aureus (MSSA). The mother was prescribed an oral antibiotic and her symptoms resolved within forty eight hours.

Swabbing and lab analysis is the only way to conclusively identify the presence of candida on the breast and rule thrush in or out. So if in doubt, do a differential diagnosis that includes subclinical mastitis (and other causes of breast or nipple pain) and/or swab the nipples.

*A differential diagnosis is the distinguishing of a disease or a condition from others presenting with similar signs and symptoms. – Meriam-Webster Medical Dictionary.

For further information see

Walker, M. Mammary Dysbiosis: An Unwelcome Visitor during Lactation. Clinical Lactation, 2018, 9(3).

The Breastfeeding Network ‘Thrush and Breastfeeding’ factsheet https://www.breastfeedingnetwork.org.uk/thrush-detailed/

HSE Factsheet on Sore Nipples https://www.hse.ie/file-library/nipple-pain-factsheet-for-healthcare-professionals.pdf

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