What Is FPIES (Food Protein-Induced Enterocolitis Syndrome)?

FPIES (Food Protein-Induced Enterocolitis Syndrome) is a rare type of food allergy that usually appears in babies, and that causes GI symptoms hours after a certain food is consumed. Here's what parents need to know about FPIES.

FPIES (Food Protein-Induced Enterocolitis Syndrome) is a rare type of food allergy that usually appears in babies, and that causes GI symptoms hours after a certain food is consumed. It's considered a non-IgE-mediated food allergy. Here's what parents need to know about FPIES, including symptoms and differences from "traditional" food allergies.

What is FPIES?

FPIES (Food Protein-Induced Enterocolitis Syndrome), usually pronounced F-Pies, is a rare type of food allergy that causes symptoms in the GI tract. These symptoms usually appear 2-4 hours after someone eats a food that they are allergic to, but could appear up to 8 hours after consuming the food. The "enterocolitis" part of FPIES describes inflammation of the intestines, which results in the GI symptoms.

We don't know what exactly causes FPIES--- the mechanisms behind it aren't widely understood. But we do know that it involves an immune system response to specific foods.

Sometimes, FPIES is misdiagnosed as repeated occurrences of a bad stomach bug (GI virus or bacterial infection) at first, because the symptoms are so similar. But then, it is correctly identified when the symptoms are consistently tied back to a specific food or foods.

Any food can potentially cause symptoms of FPIES. However, the most common FPIES food allergies are to cow's milk, soy, rice, and oats. Most children with FPIES only have one or two problem foods that trigger their symptoms, but sometimes FPIES can be triggered by multiple foods in the same child.

Learn more about FPIES from Board Certified Allergist Dr. Jonathan Spergel:

Symptoms of FPIES

Vomiting and diarrhea are the two main symptoms of FPIES.

Vomiting: FPIES usually causes vomiting around 2-4 hours (but sometimes as late as 8 hours) after a child eats the food they’re allergic to. This vomiting can often be repetitive.

Diarrhea: With FPIES, diarrhea usually develops after the vomiting.

Vomiting and diarrhea can sometimes become severe, which can cause a baby or young child to become pale, feel floppy and become dehydrated.

In some cases, the severe vomiting and diarrhea may lower your baby's blood pressure. This can lead to shock, a severe symptom which drastically hinders baby's blood flow and which requires immediate emergency attention. (More details on shock are in the dedicated section below.)

FPIES may also hinder baby's growth, or cause weight loss, which may be labeled as baby's "failure to thrive." Also, it may cause dehydration, even when the vomiting and diarrhea is not severe.

In some babies, the symptoms of FPIES become increasingly severe over time because a baby is consistently eating a problem food. In cases like this, FPIES may seem like a full-body infection, and may lead to poor growth.

Symptoms of milk-based FPIES and soy-based FPIES often tend to appear in formula-fed babies, right after they start eating formula with one of these ingredients.

Symptoms of rice-based or oat-based FPIES may emerge when baby starts eating solid foods with these ingredients.

And in exclusively breastfed babies, symptoms of milk-based FPIES may emerge only when baby first consumes cow's milk products (as FPIES reactions usually don't develop through food proteins that are passed through breastmilk.)

Again, symptoms of FPIES tend to appear 2-4 hours after someone eats a food that they are allergic to, but could appear up to 8 hours afterwards.

FPIES: A Delayed Type of Food Allergy

FPIES isn't like traditional food allergies, so it's harder to detect and diagnose.

All food allergies involve an immune response, where the immune system over-defends the body against specific types of food proteins.

There are two main categories of food allergy, though. Both involve the immune system, but each involves a distinct type of response to food proteins.

The first category of food allergy is IgE-mediated food allergy, also called immediate-type food allergy. People with this type of allergy make special IgE antibodies that detect and defend against specific types of food proteins. These antibodies trigger a reaction whenever the person eats the food(s) that they are allergic to. The symptoms of an immediate-type food allergy develop seconds to hours after consuming a problem food, and look like more "traditional" food allergy symptoms.

The second category of food allergy is non-IgE-mediated food allergy, or delayed-type food allergy. FPIES is in this category--- it is a delayed type of food allergy.

Delayed-type allergies still involve the immune system, but they don't involve IgE antibodies. This makes FPIES, and other delayed-type food allergies, much harder to identify and diagnose. After all, traditional allergy testing looks for specific IgE antibodies, but people with FPIES don't produce these antibodies.

Also, delayed-type food allergies like FPIES don't cause hives, redness and swelling, which are three of the symptoms involved in "traditional" food allergies. Instead, delayed-type food allergies cause GI symptoms (symptoms that involve parts of the gut).

FPIES reactions also develop hours after someone eats a food that they are allergic to. (This is why FPIES is called a delayed-type food allergy.) So, it can be even harder to connect the GI problems with a specific food, and diagnose the source of the problems as FPIES.

Severity of FPIES: Be Alert For Shock

FPIES doesn't usually cause life-threatening anaphylaxis like traditional food allergies do. Also, reactions caused by FPIES hardly ever require epinephrine (an Epi-pen injection). There have been no reported deaths from FPIES.

But FPIES can still be severe. And sometimes, babies with FPIES who develop severe vomiting and diarrhea can develop a dangerous condition known as shock. The International FPIES Association estimates that "up to 20% of FPIES reactions result in low blood pressure or shock."

Shock occurs when baby’s body isn’t getting enough blood flow (poor blood circulation or severely low blood pressure).

We don't yet fully know why FPIES can lead to shock. But it may result from fluids leaking out of the blood vessels and into the gut.

Shock requires immediate emergency treatment---call 911 right away if your child experiences shock.

Be alert for these symptoms of possible shock:

  • Pale or bluish skin
  • Lethargy (appearing overly tired)
  • Reduced consciousness
  • Seeming more upset/irritated than usual
  • Confusion
  • Faster or weaker pulse
  • Faster, shallower breathing
  • Dizziness or fainting
  • Extreme dehydration

Even though an Epi-Pen works to treat severe allergic reactions in people with "traditional" food allergies, the International FPIES Association reports that an Epi-Pen is not an effective treatment for shock caused by FPIES. Instead, your child will usually need fluids replaced if they develop shock. They will need a doctor to give them the fluids through an IV, to help restore normal blood flow.

Since severe vomiting and diarrhea can lead to shock, be preemptive. If your baby experiences severe vomiting or diarrhea, take them to a doctor right away so they don’t develop shock.

Diagnosing FPIES

No skin prick test or blood test can accurately diagnose FPIES, because allergy tests check for IgE antibodies.

Usually, a doctor (often an allergist or gastroenterologist) will diagnose FPIES by examining your child's medical history and symptoms, and by excluding any other illnesses that could cause similar symptoms. They will ask you how often reactions occur, and what your child has eaten, to develop a timeline of reactions. Their aim is to identify patterns: what foods your child consistently eats hours before each round of symptoms emerge. So, be ready to supply all the information you have.

To help diagnose FPIES, your doctor may also ask you to remove the food(s) that could be responsible for the allergy from your baby’s diet.

If you're feeding baby formula that contains the suspected food, you'll need to switch formulas, in consultation with your doctor.

For example, if you think that cow's milk is triggering the symptoms, stop feeding baby milk. This includes selecting a baby formula without cow's milk if you're formula feeding. Then, see if the symptoms improve after you’ve removed the food, and report back to your doctor.

An oral food challenge may also be used to diagnose FPIES. This involves feeding your child small amounts of a suspected food allergen under an allergist's close supervision. The allergist will see if your child develops FPIES symptoms hours after they consume the food. But often, an oral food challenge is not necessary.

Managing FPIES

There is no cure for FPIES. To manage FPIES, you’ll need to figure out which food(s) cause the allergic reaction, and completely remove the troublesome food(s) from your baby’s diet. Again, if your baby is formula-fed, and a formula ingredient is the problem food, you'll need to switch baby formula in consultation with your doctor.

Fortunately, though, FPIES often resolves on its own as your child gets older.

Children with FPIES often outgrow it at or around 3 years of age, and will almost always outgrow it before adulthood.

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