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A parent's guide to FPIES

Introducing solids to a baby is an exciting time for parents. The joy of seeing an infant’s reaction upon eating new foods and textures is a development families look forward to. Yet when a child has an unexpected reaction or allergy to food it can be scary. One rare reaction that can emerge during the introduction of solids is food protein-induced enterocolitis syndrome (FPIES).


 What is FPIES?

You probably have not heard about FPIES unless it has personally impacted your family. FPIES only affects around 0.5 percent of children in America.1 If that sounds like a small number, that is because it is. Still, it is more common than one might think.


This syndrome is a delayed gastrointestinal (GI) food allergy with many triggers.1 It is thought that an adverse reaction to certain proteins causes the GI tract to become inflamed.2 This changes how penetrable the GI lining is and causes fluid to shift in the body. You may hear it referred to as a non-IgE-mediated food allergy which means the onset of the reaction is not immediate.


Up to 80 percent of children are only allergic to one food, and the rest have multiple triggers.2 FPIES commonly occurs before a child’s first birthday when solids or formulas are introduced. It differs from other allergies in that the onset takes a few hours to present and there is a lack of respiratory symptoms.1 

 What are the symptoms?

It’s breakfast time. You feed your child some baby oatmeal and continue with your day. A few hours pass. Suddenly, your child begins to vomit profusely. Then the diarrhea, lethargy, and pale appearance set in. Sound scary? It is. But this is what a typical presentation of FPIES can look like.


The most common symptom of FPIES is projectile vomiting one to four hours after ingesting the offending food.1 Some other common signs and symptoms include:


  • Appearing limp

  • Lethargy

  • Appearing pale

  • Diarrhea

  • Trouble gaining weight


Dehydration can result in low blood pressure in severe presentations.1 Because of this effect on blood pressure, shock is the most concerning complication instead of anaphylaxis like other allergies. It is estimated that 15 percent of FPIES reactions result in hypotension.


 How is it diagnosed?

There is no specific test to definitively tell parents their child has FPIES.2 Providers diagnose this condition based on symptoms and on the outcome when triggers are avoided. Sometimes a provider will attempt an oral food challenge. Certain lab values may also be abnormal such as a high neutrophil count and the presence of anemia.2 Skin prick testing is not able to determine offending trigger foods.


 What is the prognosis?

There is a silver lining when it comes to FPIES. Usually by five, children tend to outgrow it.1,4 Until then careful nutritional planning is necessary. Consulting a nutritionist or dietician is wise.



FPIES infants face the threat of nutritional deficiencies because of their limited diet.2 Infant growth should be monitored closely. Advancing an FPIES-affected child’s diet is difficult. It is important to continue to give children developmentally suitable foods such as those with new textures. This can help avoid food aversions and promote appropriate feeding skills.2,4


 What is the treatment?

Treatment relies on knowing your child’s trigger foods and avoiding them. Common triggers include:1,2


  • Oats

  • Rice

  • Cow milk

  • Soy

  • Fish

  • Egg

  • Certain vegetables and fruits


If a baby experiences an FPIES reaction at home, it is suggested to take them to the emergency department if vomiting occurs repetitively and if lethargy is present.2 Rehydration through intravenous access may be indicated in these cases. Providers may also advise steroids, antiemetics, supplemental oxygen, and or vasopressors if hypotension is severe enough.


Slow progression of an infant’s diet is recommended. Parents should introduce one new food at a time. Having a few-day wait period before trying another new food is suggested. Reintroducing trigger foods at home is not advised.2 With provider supervision, food challenges to test tolerance should wait up to 18 months since the last reaction.


 Breastfeeding and formula considerations

Breastfeeding mothers may worry about ingesting the triggering foods themselves before nursing. This is only a concern if the baby’s FPIES symptoms begin during breastfeeding. If the baby appears asymptomatic and has a stable weight it is not advised for the mother to change their diet.


In formula-fed babies with a cow milk or soy triggered reaction the recommendation is to use a hydrolyzed casein-based formula. If this formula exacerbates the reaction, then an amino acid-based formula may be helpful. Always follow a provider's specific recommendations.


 Can adults have FPIES?

The vast majority of those with FPIES are children under five years old. That does not mean adults are incapable of FPIES. In America, there is an estimated 0.22 percent of citizens over 18 who are diagnosed with FPIES.4 Symptoms are similar between infants and adults. Seafood is the most common trigger in the adult population, specifically shellfish.


In adult-onset FPIES, the trigger food is often ingested repeatedly without incident beforehand. Then, out of the blue, symptoms develop. This begs the question of why adults suddenly exhibit an adverse reaction to a certain protein.4



Having a child with a deviation from healthy is overwhelming. When it is a rarely talked about deviation, the uncertainty amplifies. FPIES does not get a lot of publicity, but it should because worldwide it is the most prevalent non-IgE-mediated food allergy.4 


Management of FPIES includes avoiding trigger foods. Implementing supportive measures if a reaction occurs is needed. The prognosis of FPIES is positive with most kids outgrowing it by school-age. Due to the unpleasant characteristic symptoms of FPIES, parental anxiety can be high surrounding food. Seeking provider support can help parents feel less scared and assist with diagnosis, management, and the optimization of nutrition.



1.     Nowak-Wegrzyn A, Gupta R, Brown-Whitehorn TF, Cianferoni A, Schultz-Matney F, Gupta R. Food protein–induced enterocolitis syndrome in the US population–based study. J Allergy Clin Immunol. 2019;144(4):1128-1130. doi: 


2.     Leonard SA, Pecora V, Fiocchi AG, Nowak-Wegrzyn A. Food protein-induced enterocolitis syndrome: a review of the new guidelines. World Allergy Organization Journal. 2018;11:4. doi:


3.     Calvani M, Anania C, Bianchi A, et al. Update on food protein-induced enterocolitis syndrome (FPIES). Acta Biomed. 2021;92(7):e2021518-e2021518. doi: 


4.     Mathew M, Leeds S, Nowak-Węgrzyn A. Recent update in food protein-induced enterocolitis syndrome: pathophysiology, diagnosis, and management. Allergy, Asthma & Immunology Research. 2022;14(6):587. doi: 

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