Food Protein-Induced Enterocolitis Syndrome (FPIES) is a severe, non-typical food allergy that primarily affects the gastrointestinal tract of infants and young children. Unlike common food allergies that trigger immediate symptoms, FPIES involves a profound, delayed reaction hours after the ingestion of a trigger food protein. Because its symptoms often mimic a severe stomach virus or sepsis, FPIES is frequently misdiagnosed during the initial episodes. This condition is classified by its distinctive immune pathway and its potential for causing significant dehydration and shock.
Understanding the FPIES Mechanism
FPIES is classified as a non-immunoglobulin E (non-IgE) mediated food allergy, which fundamentally distinguishes it from immediate-type allergies like anaphylaxis. Typical allergies involve IgE antibodies, which cause the rapid release of chemicals like histamine. FPIES, conversely, is primarily a T-cell-mediated hypersensitivity reaction.
This cell-mediated response results in a delayed inflammatory cascade that directly affects the digestive system. When the offending food protein is consumed, specialized immune cells called T-cells become activated within the gut lining. These activated T-cells then release pro-inflammatory signaling proteins, known as cytokines, into the digestive tract.
The release of these cytokines causes acute inflammation in the small and large intestines, termed enterocolitis. This inflammation disrupts the normal function of the gut lining, leading to increased permeability and the characteristic gastrointestinal symptoms. This explains why the reaction is delayed, typically occurring one to four hours after ingestion.
Recognizing Symptoms and Common Triggers
The clinical presentation of FPIES is divided into two distinct forms: acute and chronic. Acute FPIES is the more common form, characterized by profuse, repetitive, and often projectile vomiting, typically beginning one to four hours after the trigger food is eaten.
The intense vomiting rapidly leads to dehydration, pallor (pale skin), and severe lethargy. Up to 20% of children may progress to hypovolemic shock. Diarrhea, which can sometimes be watery or bloody, often follows the vomiting, usually appearing five to ten hours post-ingestion.
Chronic FPIES occurs when a child consumes a trigger food regularly, resulting in persistent, lower-grade symptoms. This form involves intermittent vomiting and diarrhea, sustained over days or weeks. Continuous inflammation often leads to unintended weight loss and a failure to thrive due to poor nutrient absorption.
While any food protein can cause a reaction, the most common triggers are cow’s milk and soy, particularly in infants consuming formula. Among solid foods, the most frequent culprits are grains, specifically rice and oats. Most children react to only a single food, but some may be sensitive to multiple proteins.
Diagnosis and Emergency Treatment Protocols
Diagnosing FPIES relies heavily on a detailed clinical history. Standard allergy tests, such as skin prick tests and IgE blood tests, typically yield negative results due to the non-IgE nature of the allergy. A diagnosis is established by observing the hallmark symptoms—delayed, repetitive vomiting and lethargy—and confirming symptom resolution upon eliminating the suspected food.
The gold standard for confirming the diagnosis and resolution of FPIES is a supervised Oral Food Challenge (OFC). This procedure involves administering a measured amount of the suspected trigger food in a controlled medical environment. The patient is then closely monitored for a reaction over several hours.
Emergency Treatment
Emergency treatment for an acute FPIES reaction focuses on reversing the consequences of severe fluid loss. The most important step is the immediate administration of intravenous (IV) fluids to correct dehydration and prevent or treat hypovolemic shock. For cases with persistent vomiting, antiemetic medication, such as ondansetron, is often given to stop the emesis and allow for effective rehydration. In the most severe reactions, corticosteroids may also be administered intravenously to help reduce the inflammatory response.
The Long-Term Outlook
The prognosis for children with FPIES is generally favorable, as the condition is temporary. The majority of children outgrow their food triggers, with resolution typically occurring between three and five years of age. The timeline for tolerance acquisition varies depending on the specific food protein involved.
Cow’s milk and soy FPIES tend to be more persistent, often resolving later than reactions to solid foods like rice or oats. Resolution is confirmed through a repeat Oral Food Challenge (OFC), typically scheduled every 12 to 18 months after the initial diagnosis. Successful completion of an OFC means the food can be safely reintroduced into the child’s regular diet.
Until tolerance is confirmed, strict avoidance of the trigger food remains the primary management strategy. Children with FPIES can maintain normal growth and nutritional status while they wait to outgrow the condition. The condition rarely persists into adulthood, though adult-onset FPIES, often triggered by seafood, has been documented.