FPIES –What Who When Which Why and How?

If there’s one thing we know about, it’s rare conditions that most people have never heard of. And if there’s one thing we like to do, it’s to help spread the word about those conditions! Today we want to share about one of the most curious conditions – FPIES. If you’re new to this disease, we’ll give you some of the basics. If you’re here because you have a child with FPIES, we’ll share some information that might be helpful, link you to other families’ stories as well as some expert interviews. This blog is a primer on Food Protein-Induced Enterocolitis (FPIES), recapping and highlighting information, past references and resources. Here we go!


Pronounced like the letter “f” followed by the word “pies.” If you’ve never heard of it, allow us to help! FPIES stands for food protein-induced enterocolitis syndrome and is an allergic reaction in the digestive tract.

When someone says they have a food allergy, most people think of symptoms like anaphylaxis or hives or an itchy, swollen mouth. Those don’t happen with FPIES. Food protein-induced enterocolitis sydrome is a non-IgE-mediated immune reaction in the gastrointestinal (GI) system to one or more specific foods. This means that the IgE antibodies associated with many food allergies are not involved in an FPIES reaction. That makes FPIES hard to test for. More on that below.

Unlike most food allergies, FPIES reactions usually begin several hours after ingestion of the causative food. Often vomiting occurs 2 hours after eating a trigger food. For some people with FPIES diarrhea will follow around 5 hours after eating. Some children experience relatively mild symptoms, while others, about 20%, will have extreme reactions and may become seriously dehydrated and go into shock and need to go to the emergency department for treatment.

WHO can get FPIES?        

FPIES affects both boys and girls, typically when they are infants and young children, starting within the first year of life. While it usually affects young children, it’s thought that FPIES can affect anyone at any age, although reports of FPIES in adults have been rare and not well studied. At this time we don’t really know how many infants or children have FPIES, or the likelihood of a newborn developing FPIES. Hopefully we’ll have better data in the coming years!

WHEN do people “get” FPIES, and when will it likely go away?               

Often FPIES shows up when a baby first starts formulas or solid foods. It is not uncommon for a baby with FPIES to successfully breastfeed, only to have FPIES symptoms show up when a cow milk or soy infant formula enters her diet. In rare circumstances, FPIES has occurred in exclusively breastfed babies. Many children outgrow FPIES by age three, but this can vary based on how severe their symptoms are and which foods they react to.

WHICH foods are FPIES triggers?

In the United States, cow milk and soy are the most common FPIES triggers. However, ANY foods can cause an FPIES reaction. Some foods that aren’t typically considered likely to be allergens are common food triggers for FPIES patients, like rice and oats. Fruits and vegetables are also not unusual as triggers among FPIES patients. Weird!

HOW is FPIES diagnosed and managed?

It can be difficult to diagnose FPIES because blood allergy tests only look for IgE-mediated food allergies. In fact, there is no valid laboratory test for FPIES yet. Usually FPIES is suspected after multiple reactions, because FPIES reactions are often mistaken for a stomach bug.

Once FPIES is suspected, the only way to diagnose it with certainty is to do an oral food challenge. This is where the healthcare team gives a patient the suspected allergen and watches them to see what happens. If the symptoms happen again, that’s a positive FPIES diagnosis! For infants diagnosed with FPIES, introducing new foods slowly – one at a time and for up to three weeks – is extremely important to identify both safe and trigger foods.

Once there’s suspicion of FPIES, there’s nothing to do but avoid the trigger foods and wait. Similar to many other food allergies, children usually outgrow FPIES within a few years. The healthcare team will often advise avoiding the problem food for a certain period of time and then conducting a “challenge” to see if the allergy has been outgrown. (A challenge is when you or your child consumes the problem food again to see if it still triggers a reaction. Often under medical supervision!)

Formula-fed infants with FPIES to milk need formula a hypoallergenic formula like Neocate, as standard baby formula will trigger FPIES. Up to half of infants with FPIES to milk will also have FPIES to soy, so healthcare teams usually don’t recommend a soy formula. FPIES to milk lasts beyond the first birthday, experts recommend a hypoallergenic formula to ensure a source of key nutrients in the diet. For toddlers and children with FPIES, especially to multiple foods, a hypoallergenic formula can help supplement the elimination diet. For some children who have fewer triggers treatment is simply to avoid those foods.

I still have more questions!

That’s great! We’re glad you’re curious. We think FPIES is fascinating. It’s just too bad that FPIES symptoms are so scary and that it takes so long to get answers for many families. To learn more about FPIES we recommend checking out some of our previous articles about this interesting allergic condition:

Listen to one of the allergists who’s helped conduct research on FPIES to break down the ins and outs of FPIES in this Fact vs. Fiction video:

Watch this video to learn more about FPIES through the stories of several families and interviews with experts, sponsored by Neocate: 

What support is there for families with FPIES?

If your little one has FPIES, check out the I-FPIES at FPIES.org. This forum is a great way to learn more and connect with other families managing FPIES! 

FPIES Foundation has a spot for KIDS with FPIES. Check out their Kids in Action, Brag Board and Ways to Cope, designed with and for kids.

Kids with Food Allergies is a go-to resource as well. They offer daily assistance and practical food allergy management help and have a large online peer support group focused solely on children’s food allergies. Registration is free and a good place for giving and getting help with food ideas, recipes and cooking challenges!

While there are lots of questions we don’t have the answers to yet, we’re learning more about FPIES every day. What else can we tell you about FPIES?


Last updated July 2020

Published: 04/05/2016
Carolyn Ricciardi
Hi Elaine, Thank you for clarifying. It is possible that she would not react to a smaller amount of rice cereal. Generally, with FPIES, when trying to determine triggers, a clinician may recommend a slow introduction of higher risk foods like rice (for example: 1 teaspoon on Day 1, 2 teaspoons on Day 2, 1 tablespoon on Day 3, etc). However, a slow introduction is not required for every food. It's best to discuss with your doctor or dietitian how gradual a food introduction should be for your child.
Dear Carolyn,, Thank you so much for your response. I would like to rephrase my question to see if you could help me clarify something about a baby having FPIES. We fed her rice cereal as her first food for a week. We started with one Tablespoon (as was recommended on the box of organic rice cereal). On one occasion, during the first week of having the cereal, (having one Tablespoon or a Tablespoon and a half), the baby had an episode of vomiting. She had oat cereal for a few days and then carrots for a few days after the week of rice cereal and she seemed fine. After having rice cereal again, she had a severe vomiting episode. The pediatrician said it could be FPIES. My question is, could giving her a Tablespoon (instead of a teaspoon) to start out with the rice cereal have caused the allergic reaction or does the amount given to her not matter. That is, would she have presented with the allergic reaction whether we gave her one teaspoon or a Tablespoon for a week? Would the amount give to her for a week have caused the allergic reaction or does the amount not matter with FPIES? Thank you again, Elaine
Carolyn Ricciardi
Hi Elaine, Rice is a common allergen for FPIES kids, so if your child has FPIES, their doctor or dietitian will likely recommend a slow introduction with monitoring. This will allow you to gradually increase the amount of rice cereal your child is consuming over time until they are able to consume an age appropriate amount with (hopefully!) no reaction. We recommend you contact your little one's health care team for guidance on the introduction of FPIES allergens. Best of luck to you both!
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