Food Protein-Induced Enterocolitis Syndrome (FPIES) in Babies

Published: February 19, 2026

Last Updated: February 19, 2026

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Food Protein-Induced Enterocolitis Syndrome (FPIES) is an increasingly recognized delayed food allergy that affects the gastrointestinal system. Our pediatric pros explain what foods commonly trigger FPIES—and how to know if your baby has it. 

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What is FPIES? 

FPIES, or Food Protein-Induced Enterocolitis Syndrome, is a food allergy that affects the gastrointestinal system, causing vomiting and sometimes diarrhea. Unlike classic food allergy reactions that frequently occur within minutes of eating an allergenic food, FPIES reactions don’t begin until hours after consuming a particular food trigger. For this reason, FPIES is sometimes known as a delayed food allergy or non-IgE-mediated food allergy.

FPIES is rare in exclusively-breastfed infants, but is more commonly identified in formula-fed babies who are reacting to an ingredient in the formula. The classic presentation of FPIES is an infant who recently switched from breast milk to formula or who has started solid food. A baby with FPIES typically begins vomiting between 1 to 4 hours and may also develop diarrhea between 5 to 10 hours after eating the trigger food. Other symptoms can include low blood pressure, low body temperature, extreme pallor, and significant dehydration. 

Symptoms of FPIES

Acute FPIES

The most common symptoms of FPIES are vomiting and diarrhea, and these are frequently seen in other childhood illnesses. Because an FPIES reaction is delayed, sometimes it is misunderstood to be a stomach bug, rather than an allergic reaction to a food eaten hours earlier. FPIES is often identified when symptoms occur again after eating the same food at a later date.

Chronic FPIES

Chronic FPIES is usually seen in younger babies, typically in infants who are fed formula containing cow’s milk or soy, which are common FPIES trigger foods.

Symptoms of chronic FPIES are more persistent, and appear when larger quantities of a trigger food are consistently consumed, which is typical with infant formula. When a baby has chronic FPIES, they may develop progressive vomiting and frequent diarrhea (often with blood in the stool). If left untreated, they may become dehydrated, gain weight slowly, and suffer from metabolic acidosis (when the body has too much acid). 

Regularly eating small quantities of a trigger food can result in vomiting and diarrhea that reoccur, but are not consistent. This can happen with breastfed babies, who may react to traces of an FPIES trigger food in breast milk hours after nursing, but may not react the next time they feed. In these cases, chronic FPIES can lead to slower-than-normal weight gain, while dehydration and acidosis are less common.

Symptoms of chronic FPIES generally improve within 3 to 10 days of elimination of the trigger food from the diet.

FPIES Trigger Foods

Common foods that trigger FPIES vary by region, reflecting differences in foods typically introduced during infancy and early childhood. The most common food triggers of FPIES are cow’s milk products (including infant formula), soy, oats, and rice, followed by other foods such as avocado, banana, barley, eggs, green beans, peas, meats, poultry, seafood, squash, and sweet potatoes. 

As families have started introducing peanut earlier in infancy, it has emerged as an increasingly recognized trigger for FPIES, though it is still not common. More research is needed in this area to balance the importance of prevention of IgE-mediated peanut allergy with this demonstrated increase in peanut-triggered FPIES.

Most babies with FPIES are triggered by only 1 or 2 food types. 

Babies with FPIES do not need to delay the introduction of all commonly recognized FPIES triggers as they start solids, nor do they need to eliminate all commonly recognized FPIES triggers from their diets, especially if they are already eating that food without issue. 

How to Test for FPIES

There are no validated tests to confirm the diagnosis of FPIES. Standard allergy tests, like skin prick tests or blood tests for an IgE allergy, are usually negative in FPIES because it’s a different type of immune reaction. Rather, FPIES is a clinical diagnosis, made after a detailed history, physical examination, and testing have ruled out other conditions. 

If an FPIES diagnosis is in doubt, or if a baby is suspected to have outgrown an FPIES allergy, doctors may recommend a medically supervised oral challenge to the suspected trigger food. Vomiting during the challenge would confirm the diagnosis or persistence of the FPIES allergy. However, if the challenge food is well-tolerated, the food can typically be reintroduced into the diet.

FPIES Treatment

Treatment for FPIES is different from the treatment of IgE-mediated allergies. For acute FPIES reactions, preventing dehydration and shock are the immediate priority, with anti-nausea medications to halt vomiting, oral and intravenous rehydration to replace fluids lost from vomiting and diarrhea, and in some cases, steroids to reduce inflammation. Your doctor can help you create a plan to temporarily remove the FPIES trigger food from the diet and eventually reintroduce it.

Thankfully, most cases of FPIES will completely resolve during toddlerhood. However, FPIES to seafood unfortunately tends to be life-long. Babies with FPIES should be under the care of an allergist/immunologist and are best served by a multidisciplinary team that also includes their general pediatrician or family practitioner, a pediatric gastroenterologist, and a registered dietitian.

Frequently Asked Questions 

What causes FPIES in babies? 

The exact cause of FPIES is not fully understood, but it involves an unusual immune response that is different from classic food allergies. Instead of IgE antibodies causing immediate symptoms like hives or wheezing, FPIES triggers a delayed reaction in the gut after a trigger food is eaten. This reaction activates certain white blood cells and inflammatory signals, leading to symptoms such as repeated vomiting, lethargy, and sometimes dehydration. There is no evidence that FPIES is caused by parental feeding choices — it is not the result of introducing foods or formula too early, too late, or in the “wrong” way.

Does family history of allergies increase the risk of FPIES? 

A family history of allergies, eczema, or asthma may be more common in babies with FPIES, but it does not reliably predict who will develop it. Many babies with FPIES have no family history of food allergy, and having allergic relatives does not mean a baby will develop FPIES.

Do FPIES trigger foods need to be introduced the same way as common food allergens?

No, unless the food is a common food allergen like cow’s milk, egg, or peanut. Commonly recognized FPIES triggers can be introduced normally in the diet, without any need for gradual or stepwise introduction. 

If your baby is diagnosed with FPIES, talk to your doctor. They may recommend a more cautious introduction of other commonly recognized trigger foods because up to half of babies with FPIES react to more than one food.

Baby spit up or vomited while eating. Is it FPIES? 

No. Vomiting due to FPIES typically happens 1 to 4 hours after mealtime. Spitting up and vomiting while eating usually happens when a baby gags. Gagging is normal and naturally happens when food that is not ready to be swallowed makes its way toward the back of the throat, or when mashed foods stick to the roof of the mouth or back of the tongue where the gag reflex is triggered. Check out How to Help Baby Gagging on Food for guidance. 

Baby tried a food and had no FPIES symptoms. Can FPIES show up the next time? 

Yes. With FPIES, the first exposure may seem fine, and symptoms often appear after a repeat feeding once the immune system has been “primed.” This delayed pattern is common and can make FPIES harder to recognize at first.

Does FPIES show up on an allergy test? 

No. Standard allergy tests, like skin prick tests or blood tests for IgE, are usually negative in FPIES because it’s a different type of immune reaction. FPIES is diagnosed based on history and symptom patterns, not allergy testing.

My baby has been diagnosed with FPIES. Now what?

An FPIES diagnosis can feel overwhelming, but the next steps are usually very manageable. You’ll work with your child’s healthcare team to identify and avoid trigger foods, create a clear plan for managing reactions, and continue introducing other foods so your baby’s diet can keep expanding safely. Reintroduction of known FPIES triggers must be pursued carefully, and (for most foods) only after 12 to 18 months have gone by without experiencing a reaction. Reintroduction may be considered sooner for FPIES triggers such as cow’s milk and soy, for which the allergy is often outgrown faster than for other FPIES triggers.

When introducing new foods to baby with FPIES, are certain foods more or less risky?

After an FPIES diagnosis, most foods can still be introduced normally, and continuing to expand your baby’s diet is important for nutrition and feeding skills. Foods that are more commonly linked to FPIES may be introduced more slowly and step-by-step, with guidance from your healthcare team, so families can move forward with confidence rather than fear.

Does FPIES get worse over time? 

FPIES reactions don’t reliably get worse with each exposure, but repeatedly eating a trigger food can lead to similar or sometimes more severe symptoms. The good news is that most children outgrow FPIES over time, especially with careful avoidance and guided reintroduction.

Do babies outgrow FPIES? 

Yes. Most babies do outgrow FPIES, often in early childhood as their immune systems mature. However, some triggers can persist longer for certain children, which is why reintroducing foods is usually done thoughtfully and with medical guidance rather than by age alone.

Can FPIES be cured? 

There is no curative treatment that makes FPIES go away immediately, but it is a condition many children outgrow naturally over time. Management focuses on avoiding trigger foods, treating reactions if they occur, and periodically reassessing tolerance with medical guidance.

My doctor is unfamiliar with FPIES. What do I do?

If your doctor isn’t yet familiar with FPIES, you’re not alone—it’s often underrecognized, even though we now know it’s more common than once thought. There are excellent, evidence-based resources from FPIES advocacy groups like The FPIES Foundation and International FPIES Association that you can share, and most doctors genuinely welcome the opportunity to learn more so they can better care for your child and others with FPIES. Feel free to ask for a referral to a pediatric allergist or gastroenterologist for specialized support.

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Written By

S. Bajowala, MD, FAAAAI. Board-Certified Allergist & Immunologist

K. Rappaport, OTR/L, MS, SCFES, IBCLC, Feeding and Swallowing Specialist