Feeding & Eating

My Stored Breast Milk Smells Soapy or Sour (High Lipase)

Medically reviewed by Dr. Rachel Kim, MD, RDN · Pediatric Nutrition Specialist

Content reviewed against published La Leche League, KellyMom, CDC guidelines

Editorial policy

Last reviewed:

Feeding challenges are one of the most common concerns new parents face. When it comes to my stored breast milk smells soapy or sour (high lipase), here is what the guidelines recommend.

The short answer

If your stored or thawed breast milk smells soapy, metallic, or sour — but was stored properly — you likely have high lipase activity. Lipase is a naturally occurring enzyme in breast milk that breaks down fats. In some mothers, lipase is especially active and begins breaking down fats quickly, creating an off-putting smell and taste. High lipase milk is not spoiled or harmful to your baby. However, many babies refuse it because of the taste. The solution is scalding fresh milk before storing it, which deactivates the lipase.

Key takeaways

  • If your stored or thawed breast milk smells soapy, metallic, or sour — but was stored properly — you likely have high lipase activity. Lipase is a naturally occurring enzyme in breast milk that breaks down fats. In some mothers, lipase is especially active and begins breaking down fats quickly, creating an off-putting smell and taste. High lipase milk is not spoiled or harmful to your baby. However, many babies refuse it because of the taste. The solution is scalding fresh milk before storing it, which deactivates the lipase.
  • Usually normal when: Your fresh breast milk smells and tastes fine but develops a soapy or metallic smell after several hours in the fridge or after thawing — this is classic high lipase
  • Call your doctor if: Your baby shows signs of illness after consuming stored milk — vomiting, diarrhea, fever — seek medical evaluation, as this may indicate contaminated (not just high lipase) milk
“The AAP recommends exclusive breastfeeding for approximately 6 months after birth. Furthermore, the AAP supports continued breastfeeding, along with appropriate complementary foods introduced at about 6 months, for 2 years or beyond.”
— Breastfeeding and the Use of Human Milk, American Academy of Pediatrics (AAP)

Parents everywhere have the same worry. You are doing the right thing by looking into it.

What Parents Should Know

According to La Leche League, KellyMom, CDC guidelines, if your stored or thawed breast milk smells soapy, metallic, or sour — but was stored properly — you likely have high lipase activity. Lipase is a naturally occurring enzyme in breast milk that breaks down fats. In some mothers, lipase is especially active and begins breaking down fats quickly, creating an off-putting smell and taste. High lipase milk is not spoiled or harmful to your baby. However, many babies refuse it because of the taste. The solution is scalding fresh milk before storing it, which deactivates the lipase. At 0-6 months, high lipase is typically discovered when a parent who has been building a freezer stash of pumped milk discovers their baby refuses the thawed milk. This is devastating when you have worked hard to pump and store milk. The milk is safe — it is the taste that bothers the baby, not the quality. To prevent the taste change in future milk, scald freshly expressed milk (heat to about 180°F / 82°C — until small bubbles form at the edges, not a full boil) then cool and store immediately. It is generally considered normal when your fresh breast milk smells and tastes fine but develops a soapy or metallic smell after several hours in the fridge or after thawing — this is classic high lipase. However, you should contact your pediatrician promptly if your baby shows signs of illness after consuming stored milk — vomiting, diarrhea, fever — seek medical evaluation, as this may indicate contaminated (not just high lipase) milk.

Sources: [1], [2], [3]

Normal vs. Concerning

Usually Normal
Worth Discussing
Your fresh breast milk smells and tastes fine but develops a soapy or metallic smell after several hours in the fridge or after thawing — this is classic high lipase
Your baby shows signs of illness after consuming stored milk — vomiting, diarrhea, fever — seek medical evaluation, as this may indicate contaminated (not just high lipase) milk
Your baby drinks freshly pumped milk but refuses thawed milk
Your breast milk smells foul (rotten, not soapy) even when fresh — this is not a lipase issue and may indicate bacterial contamination
Scalding before storage fixes the taste issue
Your baby is refusing all milk (fresh and stored) and is not gaining weight

By Age

What to expect by age

0-6 months

High lipase is typically discovered when a parent who has been building a freezer stash of pumped milk discovers their baby refuses the thawed milk. This is devastating when you have worked hard to pump and store milk. The milk is safe — it is the taste that bothers the baby, not the quality. To prevent the taste change in future milk, scald freshly expressed milk (heat to about 180°F / 82°C — until small bubbles form at the edges, not a full boil) then cool and store immediately.

6-12 months

If you have a large freezer stash of high-lipase milk, there are strategies to use it: mix it with freshly expressed milk, mix it into solid foods (oatmeal, purées), or try offering it when the baby is very hungry. Some babies accept it if it is offered chilled rather than warmed. If none of these work, the milk can still be used in baths for skin benefits. Going forward, scald fresh milk before storing.

What to Tell Your Pediatrician

  • Describe when you first noticed my stored breast milk smells soapy or sour (high lipase) and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your breast milk smells foul (rotten, not soapy) even when fresh — this is not a lipase issue and may indicate bacterial contamination.
  • Mention if your baby is refusing all milk (fresh and stored) and is not gaining weight.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

What Should You Do?

When to take action

Probably normal when...
  • Your fresh breast milk smells and tastes fine but develops a soapy or metallic smell after several hours in the fridge or after thawing — this is classic high lipase
  • Your baby drinks freshly pumped milk but refuses thawed milk
  • Scalding before storage fixes the taste issue
Mention at your next visit when...
  • Your breast milk smells foul (rotten, not soapy) even when fresh — this is not a lipase issue and may indicate bacterial contamination
  • Your baby is refusing all milk (fresh and stored) and is not gaining weight
  • You are unsure whether your milk is high lipase or actually spoiled
Act now when...
  • Your baby shows signs of illness after consuming stored milk — vomiting, diarrhea, fever — seek medical evaluation, as this may indicate contaminated (not just high lipase) milk

What You Can Do at Home

  • Keep track of when you notice my stored breast milk smells soapy or sour (high lipase) — noting the time of day, duration, and any triggers can help your pediatrician.
  • Remember that your fresh breast milk smells and tastes fine but develops a soapy or metallic smell after several hours in the fridge or after thawing — this is classic high lipase — this is generally within the range of normal.
  • At 0-6 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
  • Offer feeding in a calm, distraction-free environment. Avoid forcing or pressuring your baby to eat.
  • While monitoring at home, seek immediate care if your baby shows signs of illness after consuming stored milk — vomiting, diarrhea, fever — seek medical evaluation, as this may indicate contaminated (not just high lipase) milk.

Is European Baby Formula (HiPP, Holle) Safer Than US Formula?

European formulas like HiPP and Holle are popular among US parents who believe they are higher quality. European formulas are regulated by the EU and do meet strict safety standards — but they are not FDA-regulated for the US market, meaning there is no US oversight of storage, transport, or labeling accuracy when purchased through third-party importers. Both US and European formulas are nutritionally complete and safe when used as directed. The main differences are in ingredient sourcing (European formulas tend to use organic ingredients and avoid corn syrup) and specific nutrient levels. Neither system is inherently safer than the other.

What Is Paced Bottle Feeding and Should I Be Doing It?

Paced bottle feeding (also called responsive bottle feeding) is a technique that slows down the flow of milk from a bottle to more closely mimic the pace of breastfeeding. The baby is held upright, the bottle is held horizontally, and frequent pauses are built in to allow the baby to regulate their intake. This approach reduces overfeeding, decreases gas and spit-up, supports the breastfeeding relationship for combo-fed babies, and helps all babies develop healthy hunger-fullness cues. Paced feeding is recommended by most lactation professionals for all bottle-fed babies.

My Baby Won't Switch Between Breast and Bottle (Nipple Confusion)

What is commonly called "nipple confusion" is more accurately described as flow preference. Babies are not confused — they can tell the difference between breast and bottle. Some develop a preference for the faster, more consistent flow of a bottle and become frustrated at the breast. Others, accustomed to the breast, refuse a bottle. This is common and does not mean you cannot combo-feed. Strategies like paced bottle feeding, slow-flow nipples, and timing can help babies accept both.

Guide

Feeding & Nutrition Guide

Complete guide to breastfeeding, formula feeding, and solid food introduction.

Guide

When to Call the Doctor

General guide on when to call the pediatrician, visit urgent care, or go to the ER.

Frequently asked questions

Is my stored breast milk smells soapy or sour (high lipase) normal?
If your stored or thawed breast milk smells soapy, metallic, or sour — but was stored properly — you likely have high lipase activity. Lipase is a naturally occurring enzyme in breast milk that breaks down fats. In some mothers, lipase is especially active and begins breaking down fats quickly, creating an off-putting smell and taste. High lipase milk is not spoiled or harmful to your baby. However, many babies refuse it because of the taste. The solution is scalding fresh milk before storing it, which deactivates the lipase.
When should I call the doctor about my stored breast milk smells soapy or sour (high lipase)?
Your baby shows signs of illness after consuming stored milk — vomiting, diarrhea, fever — seek medical evaluation, as this may indicate contaminated (not just high lipase) milk
When is my stored breast milk smells soapy or sour (high lipase) normal?
Your fresh breast milk smells and tastes fine but develops a soapy or metallic smell after several hours in the fridge or after thawing — this is classic high lipase Your baby drinks freshly pumped milk but refuses thawed milk Scalding before storage fixes the taste issue
What causes my stored breast milk smells soapy or sour (high lipase)?
If your stored or thawed breast milk smells soapy, metallic, or sour — but was stored properly — you likely have high lipase activity. Lipase is a naturally occurring enzyme in breast milk that breaks down fats. In some mothers, lipase is especially active and begins breaking down fats quickly, creating an off-putting smell and taste. High lipase milk is not spoiled or harmful to your baby. However, many babies refuse it because of the taste. The solution is scalding fresh milk before storing it, which deactivates the lipase. Common explanations include: Your fresh breast milk smells and tastes fine but develops a soapy or metallic smell after several hours in the fridge or after thawing — this is classic high lipase. Your baby drinks freshly pumped milk but refuses thawed milk.
What should I mention to my pediatrician about my stored breast milk smells soapy or sour (high lipase)?
You should mention my stored breast milk smells soapy or sour (high lipase) at your next visit if: Your breast milk smells foul (rotten, not soapy) even when fresh — this is not a lipase issue and may indicate bacterial contamination. Your baby is refusing all milk (fresh and stored) and is not gaining weight. You are unsure whether your milk is high lipase or actually spoiled.
Is my stored breast milk smells soapy or sour (high lipase) normal at 0-6 months?
High lipase is typically discovered when a parent who has been building a freezer stash of pumped milk discovers their baby refuses the thawed milk. This is devastating when you have worked hard to pump and store milk. The milk is safe — it is the taste that bothers the baby, not the quality. To prevent the taste change in future milk, scald freshly expressed milk (heat to about 180°F / 82°C — until small bubbles form at the edges, not a full boil) then cool and store immediately.
Is my stored breast milk smells soapy or sour (high lipase) normal at 6-12 months?
If you have a large freezer stash of high-lipase milk, there are strategies to use it: mix it with freshly expressed milk, mix it into solid foods (oatmeal, purées), or try offering it when the baby is very hungry. Some babies accept it if it is offered chilled rather than warmed. If none of these work, the milk can still be used in baths for skin benefits. Going forward, scald fresh milk before storing.
Should I go to the ER for my stored breast milk smells soapy or sour (high lipase)?
Seek emergency care if your baby shows signs of illness after consuming stored milk — vomiting, diarrhea, fever — seek medical evaluation, as this may indicate contaminated (not just high lipase) milk. When in doubt, call your pediatrician's after-hours line for guidance.
Does my stored breast milk smells soapy or sour (high lipase) go away on its own?
In many cases, my stored breast milk smells soapy or sour (high lipase) resolves on its own, especially when your fresh breast milk smells and tastes fine but develops a soapy or metallic smell after several hours in the fridge or after thawing — this is classic high lipase.
LA LECHE LEAGUEKELLYMOMCDC

References

  1. [1]La Leche League International. My Expressed Breastmilk Doesn't Smell Fresh. What Can I Do? La Leche League
  2. [2]KellyMom. What Affects the Taste and Smell of Breast Milk? KellyMom
  3. [3]Centers for Disease Control and Prevention. Proper Storage and Preparation of Breast Milk. CDC

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss My Stored Breast Milk Smells Soapy or Sour (High Lipase).

Things to mention

  • Describe when you first noticed my stored breast milk smells soapy or sour (high lipase) and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your breast milk smells foul (rotten, not soapy) even when fresh — this is not a lipase issue and may indicate bacterial contamination.
  • Mention if your baby is refusing all milk (fresh and stored) and is not gaining weight.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

Observations to share

  • Your breast milk smells foul (rotten, not soapy) even when fresh — this is not a lipase issue and may indicate bacterial contamination
  • Your baby is refusing all milk (fresh and stored) and is not gaining weight
  • You are unsure whether your milk is high lipase or actually spoiled

Urgent signs to report immediately

  • Your baby shows signs of illness after consuming stored milk — vomiting, diarrhea, fever — seek medical evaluation, as this may indicate contaminated (not just high lipase) milk

My notes

From ismybabyalright.com — free, evidence-based baby health guides

All content follows our editorial policy and is reviewed against published clinical guidelines.

2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members

Related Resources

Food Introduction GuideFeeding & Pumping GuideBaby Meal PlannerBaby Tracker

Bottom line

Most cases of my stored breast milk smells soapy or sour (high lipase) are normal. Talk to your pediatrician if your baby shows signs of illness after consuming stored milk — vomiting, diarrhea, fever — seek medical evaluation, as this may indicate contaminated (not just high lipase) milk.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

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Is European Baby Formula (HiPP, Holle) Safer Than US Formula?

European formulas like HiPP and Holle are popular among US parents who believe they are higher quality. European formulas are regulated by the EU and do meet strict safety standards — but they are not FDA-regulated for the US market, meaning there is no US oversight of storage, transport, or labeling accuracy when purchased through third-party importers. Both US and European formulas are nutritionally complete and safe when used as directed. The main differences are in ingredient sourcing (European formulas tend to use organic ingredients and avoid corn syrup) and specific nutrient levels. Neither system is inherently safer than the other.

What Is Paced Bottle Feeding and Should I Be Doing It?

Paced bottle feeding (also called responsive bottle feeding) is a technique that slows down the flow of milk from a bottle to more closely mimic the pace of breastfeeding. The baby is held upright, the bottle is held horizontally, and frequent pauses are built in to allow the baby to regulate their intake. This approach reduces overfeeding, decreases gas and spit-up, supports the breastfeeding relationship for combo-fed babies, and helps all babies develop healthy hunger-fullness cues. Paced feeding is recommended by most lactation professionals for all bottle-fed babies.

My Baby Won't Switch Between Breast and Bottle (Nipple Confusion)

What is commonly called "nipple confusion" is more accurately described as flow preference. Babies are not confused — they can tell the difference between breast and bottle. Some develop a preference for the faster, more consistent flow of a bottle and become frustrated at the breast. Others, accustomed to the breast, refuse a bottle. This is common and does not mean you cannot combo-feed. Strategies like paced bottle feeding, slow-flow nipples, and timing can help babies accept both.

When to Introduce Allergens to Baby

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I'm Worried My Baby Is Aspirating During Feeds

Aspiration means liquid or food enters the airway instead of the stomach. Occasional coughing during feeds is common and does not usually indicate aspiration. True aspiration is less common and may present as recurrent respiratory infections, a wet or gurgly voice after feeds, or chronic cough. If you are concerned, a swallow study can provide a definitive answer.

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