Anna Nowak-Wegrzyn, MD, PhD, of NYU Grossman School of Medicine.

Anna Nowak-Wegrzyn, MD, PhD

 Best Practices for Managing FPIES Reactions, With Anna Nowak-Wegrzyn, MD, PhD

 Food Protein–Induced Enterocolitis Syndrome (FPIES)

 highlights evolving strategies for both acute treatment and long-term dietary management in infants and young children. At the 

2026 American Academy of Allergy, Asthma & Immunology (AAAAI)

 annual meeting in Philadelphia, Anna Nowak-Wegrzyn, MD, PhD, from NYU Grossman School of Medicine, discussed best practices for clinicians navigating this complex non-immunoglobulin E–mediated food allergy.

FPIES most commonly begins in infancy and typically presents with delayed gastrointestinal symptoms after ingestion of a trigger food. Unlike classic allergic reactions, symptoms usually occur 1 to 4 hours after ingestion and are characterized by repetitive, often forceful vomiting, pallor, lethargy, and occasionally diarrhea. Because skin or respiratory symptoms are typically absent, the condition can initially be mistaken for viral gastroenteritis.

“It may start on the first known feeding of the food,” Nowak-Wegrzyn said. “Maybe [the] third or fourth time the baby tolerated a small amount, [but] then they are fed a larger amount, and now 2 hours later, between 1 and 4 hours after eating, they develop vomiting. Sometimes…if it's witnessed by the parent, it's described as projectile.”

Acute management strategies have evolved as clinicians better understand the underlying inflammatory pathways involved in FPIES. Nowak-Wegrzyn noted that increasing evidence supports the use of ondansetron, a serotonin antagonist commonly used to treat chemotherapy-related nausea and vomiting. During FPIES reactions, serotonin release appears to contribute to the vomiting response, making ondansetron an effective option for symptom control.

For milder reactions, management can often occur at home. Caregivers may administer oral ondansetron and begin careful oral rehydration using small, frequent amounts of fluids such as oral rehydration solutions or breast milk. However, more severe reactions require emergency evaluation.

“FPIES is considered an allergic emergency because a subset of patients may have more severe manifestations with hypotension, with really distributive hypovolemic shock, and this will not resolve unless you can provide fluid resuscitation,” Nowak-Wegrzyn said.

These patients need intravenous fluids and, in some cases, corticosteroids to reduce the inflammatory response.

Beyond acute treatment, one of the most challenging aspects of FPIES management is determining how and when to introduce new foods after a reaction. To reduce the risk of additional reactions, clinicians typically recommend introducing foods from entirely different food groups rather than closely related foods that may carry a higher risk of cross-reactivity. For example, if an infant reacts to oat, the next food introduced might be a fruit or vegetable rather than another grain.

Initial introductions are often done gradually, starting with very small amounts and slowly increasing to a typical serving size. As infants successfully tolerate more foods, the pace of dietary expansion can usually increase.

Because diagnostic tests are typically negative in FPIES, decisions about food reintroduction often rely on clinical judgment.

“We don't attempt to reintroduce the food sooner than 6 months after the reaction, but after that, we may wait longer if the child is avoiding multiple foods and hasn't introduced all of [the] other foods,” Nowak-Wegrzyn said. “We would like to avoid a situation [where] they will get turned off and unwilling to try other foods.”

Anna Nowak-Wegrzyn has no relevant disclosures.

Nowak-Wegrzyn, A. Update on Diagnosis and Management of FPIES in Early Life. Session presented at AAAAI 2026 in Philadelphia on February 27, 2026.

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At AAAAI 2026, Anna Nowak-Wegrzyn, MD, discussed the use of ondansetron, home management strategies, and guidance on the gradual reintroduction of foods in FPIES.

Best Practices for Managing FPIES Reactions, With Anna Nowak-Wegrzyn, MD, PhD

OFC Updates for FPIES in Infants, With Anna Nowak-Wegrzyn, MD, PhD

2026 American Academy of Allergy, Asthma & Immunology (AAAAI) 

annual meeting in Philadelphia, Anna Nowak-Wegrzyn, MD, PhD, of NYU Grossman School of Medicine, presented updates on the diagnosis and management of 

food protein–induced enterocolitis syndrome (FPIES)

 in infants. Updates included efforts to refine oral food challenge (OFC) protocols and improve recognition of the condition in early life.

 spoke with Nowak‑Wegrzyn during the meeting to discuss key takeaways from her session. She emphasized that despite growing clinical awareness, the condition remains fundamentally a clinical diagnosis.

“We didn't have any kind of diagnostic breakthroughs,” Nowak‑Wegrzyn said. “It’s still a clinical diagnosis, so the clinician has to be familiar with the manifestations, with the symptoms to make a diagnosis, because there's no blood test, there’s no skin test that can confirm it.”

FPIES is a non–immunoglobulin E–mediated food allergy that typically presents in infancy with delayed gastrointestinal symptoms following ingestion of a trigger food. Unlike classic immunoglobulin E–mediated food allergies, which can often be identified through skin prick testing or serum immunoglobulin E measurement, most patients with FPIES have negative results on standard allergy testing. However, a subset of patients may develop positive immunoglobulin E tests to the triggering food, a presentation sometimes described as atypical disease.

Clinically, the syndrome is characterized by delayed onset vomiting, typically occurring 1–4 hours after ingestion of the offending food. Infants may also appear pale or lethargic and can develop decreased muscle tone during episodes, symptoms that can initially resemble other serious conditions.

Because of this presentation, physicians must often consider infectious etiologies during the initial evaluation. Sepsis and viral gastroenteritis are common conditions included in the differential diagnosis.

The overlap in clinical presentation can also extend to laboratory findings. Infants experiencing a reaction may demonstrate elevated white blood cell counts with a predominance of neutrophils, a pattern that can mimic infection and complicate early diagnosis. However, symptom resolution patterns can help distinguish FPIES from infectious illnesses.

“Unlike with sepsis or viral gastroenteritis, infants have symptoms that resolve quite quickly,” Nowak-Wegrzyn said. “If they are not being fed the food, then within several hours, they…start going back to baseline. “Obviously, you have to do all of the workup right…you have to rule out infections, and only after the fact, when you know there's resolution of symptoms, there's negative tests for infectious causes, then you can conclude that this was likely food protein-induced enterocolitis syndrome reaction.”

Diagnosis becomes clearer if a child later experiences a similar reaction after re-exposure to the same food. Typically, infants remain healthy between episodes and demonstrate normal growth and development, with symptoms appearing only when the trigger food is ingested.

Beyond diagnosis, Nowak-Wegrzyn highlighted evolving recommendations regarding OFCs.

“We are changing the protocol to involve only a partial surveying of the food,” Nowak-Wegrzyn said. “We're simplifying that approach [of] the food challenge, providing guidance [on] what is the age-appropriate serving size of the most common foods like milk, egg, oat, wheat, rice, peanut… just to make it to facilitate introduction of foods.”

At AAAAI 2026, Nowak-Wegrzyn presented FPIES diagnosis in infants, emphasizing clinical recognition and updated oral food challenge protocols.

Anna Nowak-Wegrzyn, MD, PhD

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