Smelly Breast Milk - Possible Reasons

All breast milk contains two forms of lipase, enzymes that are needed to form a catalyst, or a reaction. Lipoprotein lipase (LPL) is the main one for breaking down milk fat. The bile-salt stimulating lipase (BSSL) appears to enhance the infant’s digestion of the milk and does so in as little as one-half hour within the baby’s intestines!

Most of the time, lipase is undetectable in the mother’s milk. However, once her expressed milk is left to stand out or is stored in the refrigerator or freezer, lipase brakes down the fats more quickly and can create an unpleasant or soapy odor. This smell (or the altered taste) can be objectionable to some babies.

If a mom would complain that her baby is bothered by a smell to her breast milk, there are several things to try:

  • Make sure the refrigerator is free of any smells (foods) which may affect the milk. Encourage the use of baking soda.
  • Be careful to use bottles or containers with tight-fitting lids.
  • Could there be anything in mom’s diet which could be changing the smell of her breast milk? (By the way: babies often suckle more vigorously after mom eats garlic)!
  • Thoroughly examine the milk. Very rarely, breast milk can be “spoiled” by containing an over-growth of bacteria. This milk smells rancid, or very sour. Be sure to distinguish between a soapy smell and a rancid/sour smell. Don’t give baby breast milk that has a rancid smell!

Some facts to remember: A high level of lipase is not harmful to the baby. If the baby is bothered by the soapy smell, it is better to simply feed the baby at breast, rather than pump. When mom must store her milk for later use and she knows baby won’t take the “soapy” smelling milk, she may want to scald the expressed milk by heating it in a saucepan until little bubbles form around the edges (180 degrees)…then quickly cool and store. DO NOT BOIL! Once breast milk has been refrigerated or frozen, scalding will not eliminate the smell.