How Do I Know If My Baby Needs Hydrolyzed Formula?

Hydrolyzed formula is any specialty, milk-based formula where the cow's milk proteins are broken down into smaller pieces. This makes the formula easier to digest for babies who have a milk allergy or intolerance. Today, we'll cover what hydrolyzed formula is, the different types of hydrolyzed formula, and how to tell if your baby would benefit from hydrolyzed formula.


What is hydrolyzed formula used for?

Hydrolyzed formula is one type of hypoallergenic baby formula.

It is designed for babies who have trouble digesting standard cow's milk-based formulas, and who experience GI issues, reflux, colicky crying and other symptoms when given these "regular" formulas.

Babies with allergies or intolerances to milk develop symptoms like these because they have trouble digesting and processing the fully intact cow's milk proteins in regular formula.

But in hydrolyzed formula, the cow's milk proteins are broken into smaller parts.

(The process of breaking down the proteins is called hydrolysis, so that's what gives hydrolyzed formula its name.)

This makes the proteins much easier to digest for babies with a cow's milk allergy or intolerance. So, hydrolyzed formula doesn't cause the same GI issues in milk-sensitive babies as regular formula does.


How can I tell if baby would benefit from hydrolyzed formula?

If baby has symptoms of a cow's milk allergy or intolerance when consuming standard formula, they will benefit from hydrolyzed formula.

Here's how to identify if your baby has symptoms of a milk allergy or milk intolerance.

Milk allergies

Milk allergies always involve the immune system. Normally, the immune system defends the body against harmful invaders like bacteria and viruses. But when a baby has a milk allergy, their immune system mistakenly treats milk proteins like harmful invaders. Their immune system over-defends the body against milk proteins, and triggers allergic reaction symptoms, whenever it detects these proteins.

There are two categories of milk allergies, and each produces different types of symptoms.

The first category is known as IgE-mediated milk allergy. The symptoms of this allergy type are triggered when a baby's specific IgE antibodies detect and respond to milk proteins.

In babies and young children, the most common symptoms of these allergies are:

  • Hives
  • Swelling of the face, lips, eyes, or other parts of the body
  • Vomiting
  • Lasting congestion

These and other symptoms occur seconds to hours after someone consumes cow's milk. (To learn more about all of the possible symptoms, read our guide to identifying food allergy reactions in babies.)

The second type of milk allergy is non-IgE-mediated milk allergy because this category involves the immune system, but doesn't involve IgE antibodies. (Allergies in this category are also called delayed-type milk allergies). This category of milk allergy is very rare, and includes conditions like EoE and FPIES.

Allergies in this category cause symptoms hours to days after baby consumes a milk product. These symptoms almost always involve the GI tract, and may include:

  • Vomiting
  • Reflux-like symptoms (forceful and repeated spitting up that seems painful)
  • Diarrhea
  • Abnormal stools/Loose stools
  • Stomach pain
  • Abdominal pain
  • Colicky crying (loud, prolonged, inconsolable crying)

(For more information, please read our guide to non-IgE-mediated food allergies.)


Milk intolerances

Milk intolerances are completely different from milk allergies, because milk intolerances do not involve the immune system.

Instead, milk intolerances are connected with the digestive system. When baby's digestive system can't properly break down parts of cow's milk, they have a milk intolerance.

This causes them to develop GI symptoms when they consume milk that isn't already broken down.

Some of these symptoms may include:

  • Diarrhea
  • Loose stools
  • Mucus in stools
  • Bloody stools
  • Stomach pain
  • Bloating
  • Constipation
  • Gassiness
  • Cramps
  • Abdominal pain
  • Nausea
  • Vomiting or forceful, painful spitting up
  • Colicky crying
  • Irritability after consuming cow's milk


Although these symptoms are similar to non-IgE-mediated milk allergy symptoms, milk intolerances are much more common.

Some types of milk intolerances include lactose intolerance, where the body can't properly digest the sugars in milk, and milk protein intolerance, where the body struggles to break down the proteins in milk.

If you think your baby has a milk allergy or intolerance, ask your pediatrician if you should switch to hydrolyzed formula.


Types of Hydrolyzed Formula: Two Categories

There are two categories of hydrolyzed formula: partially hydrolyzed and extensively hydrolyzed. These categories describe how broken down the proteins in hydrolyzed formula are (how small the protein pieces are).

Knowing the two categories and what babies they benefit is vital to choosing the right hydrolyzed formula for your baby's needs.


Partially hydrolyzed formulas

Partially hydrolyzed formulas contain cow's milk proteins that are broken into somewhat smaller pieces, so they're easier for a baby to digest. But the protein pieces are not as small as the ones in the other category, extensively hydrolyzed formula (which we will cover below).

Sometimes, partially hydrolyzed formulas contain a whey and casein protein blend, and other times, they only contain whey protein.

Partially hydrolyzed formulas are not suitable for babies with confirmed milk allergies.

Rather, they're meant for babies who experience colic, gassiness, and/or digestive symptoms as a result of a milk intolerance.

One way to explain partially hydrolyzed formulas is this: Think of the milk protein in traditional formula as an intact pearl necklace. What if the pearl necklace was cut in five spots, so you were left with several smaller pearl strands? This is like the milk proteins found in partially hydrolyzed formulas. Their smaller size makes these proteins easier to digest.

But they still have too much resemblance to the original protein (like the pearl strands resemble smaller, open necklaces). So, a baby with a milk allergy still recognizes these proteins, and the proteins can still cause an allergic reaction.


Extensively hydrolyzed formulas

Extensively hydrolyzed formulas contain cow's milk proteins that are broken down into extremely small parts. Specifically, they contain broken down casein or broken down whey proteins.

(The proteins in extensively hydrolyzed formula aren't broken down completely, but they are broken down between 80% and 93%.)

Extensively hydrolyzed formulas are processed enough to be suitable for babies with food allergies. It's estimated that "about 90% of babies with cow’s milk allergy will tolerate" extensively hydrolyzed formulas, according to Kids With Food Allergies.

Think back to the example with the strand of pearls, where the strands were broken down. If you broke the strands down again, into many little strings with only two or three pearls apiece, this is like the very small protein pieces in extensively hydrolyzed formula.

The proteins in this type of formula are broken up small enough that the immune system of a milk-allergic baby can’t recognize them as cow’s milk proteins. (It’s just like how the very small pearl strands are still pearl strands, but don’t resemble small necklaces anymore.) As a result, the baby usually won’t experience allergic reaction symptoms when they consume extensively hydrolyzed formula.

Extensively hydrolyzed formulas also offer more thorough relief for babies with food intolerances, although they are more expensive than partially hydrolyzed formulas.


Can I mix hydrolyzed and standard formula?

It's safe to mix hydrolyzed and regular formulas, and mixing the two when first introducing the hydrolyzed formula will help baby get used to the new formula's taste.

However, once you've completed the switch, you should probably stick with all hydrolyzed formula until your pediatrician gives the go-ahead for you to completely switch back (that is, if that happens at all).

This is because regular formula contains milk proteins that are not broken down. These intact proteins might cut down on (or completely negate) the benefits of the broken-down proteins in hydrolyzed formula. After all, the intact proteins are what caused baby to develop the symptoms that prompted the switch to hydrolyzed formula.


Switching to hydrolyzed formula

Usually, hydrolyzed formula isn't as sweet as standard formula, so baby may need time to get used to the taste. Given this, it's best to introduce hydrolyzed formula gradually.

You'll do this by mixing the hydrolyzed formula with the formula you want to stop feeding baby. Slowly add more hydrolyzed formula over a few days until baby's drinking only hydrolyzed formula.

Here's an example schedule you could use:

  • Day 1: 75% current formula, 25% hydrolyzed formula
  • Day 2: 50% current formula, 50% hydrolyzed formula
  • Day 3: 25% old formula, 75% hydrolyzed formula
  • Day 4: 100% hydrolyzed formula


Can I switch back from hydrolyzed formula to regular formula?

Whether you can successfully switch back to regular formula depends on what kind of milk sensitivity your baby has. You should also only attempt to switch back if your doctor has given you the okay.

Typically, babies with non-IgE-mediated milk allergies (delayed-type allergies) can be safely reintroduced to standard formula. So, ask your doctor about when to switch back if your baby has a delayed milk allergy.

But babies with confirmed IgE-mediated milk allergies cannot be safely introduced to regular formula. Even small amounts of intact milk proteins will consistently cause them to develop allergic reaction symptoms.

As for milk intolerances, if baby has a milk intolerance, doctors usually recommend reintroducing cow's milk to babies with milk intolerance at some point. This may include reintroducing formula that contains intact milk proteins. In this scenario, talk to your doctor about when to reintroduce standard formula.

Be advised that many babies with suspected milk allergies really only have milk intolerances. And it's safe to reintroduce regular formula to a baby with a milk intolerance.

To confirm whether or not your baby has an IgE-mediated milk allergy, they will need to undergo allergy testing.

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