Why does my breast milk smell slightly sour?

Understanding the Sour Smell of Breast Milk
Experiencing a slightly sour smell in breast milk can be concerning for nursing mothers. However, this phenomenon is often linked to natural processes and storage conditions rather than any underlying health issues.
Lipase Activity and Its Effects
One of the primary reasons breast milk may develop a sour or soapy smell is due to the activity of an enzyme called lipase. Lipase is naturally present in human milk and plays a crucial role in breaking down fats. When breast milk is expressed and stored, especially if it is frozen, lipase can continue to act on the milk, even at low temperatures. This enzymatic activity can lead to the release of fatty acids, which may impart a sour or soapy odor to the milk.
Storage Conditions Matter
The way breast milk is stored can significantly influence its smell. If milk is not stored properly—such as being left out at room temperature for too long or not sealed tightly—it can develop an “off” smell similar to that of spoiled cow’s milk. Additionally, using storage bags that are not airtight can allow external odors from the freezer to permeate the milk, further altering its scent.
Normal Variations in Milk Composition
It’s also important to note that variations in breast milk’s smell can be completely normal. Many mothers report that their expressed milk has a slightly different odor after refrigeration or thawing, often describing it as sour, metallic, or even soapy. This is generally not a cause for alarm, as it can be a natural result of the milk’s composition and the mother’s diet or hormonal changes.
What Should You Do?
If you notice a sour smell in your breast milk, consider the following steps:
1. Check Storage Practices: Ensure that your milk is stored in airtight containers and that it is not left out for extended periods.

2. Observe Your Diet: Sometimes, certain foods or supplements can affect the smell of breast milk. If you suspect this might be the case, try adjusting your diet to see if it makes a difference.
3. Consult a Professional: If the smell is accompanied by other concerning symptoms or if you are unsure about the safety of your milk, it’s always best to consult a healthcare professional or a lactation consultant for personalized advice.
In conclusion, while a slightly sour smell in breast milk can be alarming, it is often a normal occurrence linked to enzymatic activity and storage conditions. Understanding these factors can help mothers feel more confident in their breastfeeding journey.

Why does my breast milk smell funny in the fridge?

Some mums notice that their expressed milk has an ‘off’ or soapy smell and taste, even when they have handled it cleanly. This can be caused by oxidation following the normal action of enzymes in the milk designed to help the baby digest the milk fats.

Is it OK if milk smells a little sour?

Smell: If milk has a bad smell, it may indicate spoilage. Fresh milk should have a mild, pleasant aroma. A sour or off smell usually means that bacteria have started to grow, and it’s best not to consume it.

Why is my milk sour but not expired?

It’s important to note that when milk ferments. It does not spoil or become unsafe to consume. The lactic acid in the fermented milk maintains. Its safety and protects it from further spoilage.

What happens if my baby drinks sour breast milk?

If your baby has had spoiled breast milk, they’ll likely let you know. They may throw up, or have an upset stomach, diarrhea or fever. It’s important to call your pediatrician if you think your baby may be sick from having spoiled breast milk.

Can breast milk become sour in the breast?

No, breast milk doesn’t spoil inside the breast. It’s produced on demand and maintains its freshness. However, once expressed, it can spoil if not stored properly.

Why does my breastmilk smell sour?

Your milk may have excess lipase in it, which can cause stored breastmilk to smell sour or soapy. Lipase is a beneficial enzyme found in breast milk that helps break down milk fat. If your breastmilk has excess lipase, the longer the milk is stored, the stronger the smell becomes.

Is sour breast milk safe?

Human milk that has truly soured has a very distinct sour taste and odor – much like soured cow’s milk. If your milk doesn’t smell distinctly sour or rancid, then it should be safe to give to your baby.

What causes a sour milk body odor?

Besides a thyroid disorder, other contributing factors to sour-smelling sweat include: Diet and Hydration: Your diet and hydration levels can affect your body odor. Consuming certain foods like garlic, onions, spicy foods, and processed foods can release volatile compounds through sweat, causing unpleasant smells.

How to know if breastmilk is spoiled?

It will also smell bad, much like spoiled cow’s milk. And, like spoiled cow’s milk, breast milk that’s old will taste sour. (It’s fine to taste your breast milk to check!) Always label your pumped milk with a time and date so you can tell how old it is.

What causes sour breast milk?

The true cause of the sour smell and taste isn’t necessarily the amount of lipase in your milk, but the rate of lipase activity. While some moms can store milk in the refrigerator or freezer for a while with no change in smell, others notice a change after just 24 hours.