Diagnosis and Testing

Increases in Adulthood

FPIES was previously thought to only affect infants and young children, but it has now been increasingly recognized that FPIES can occur in adulthood. FPIES in adults is more common in females and is most often caused by seafood, although other foods, such as cow’s milk/dairy, egg, and wheat are being reported. The acute gastrointestinal symptoms of FPIES in adults include severe abdominal pain, cramping, severe nausea, vomiting and  / or diarrhea that start within 1-4 hours following food ingestion. However, it is important to recognize that 25-40% of adult FPIES patients may not present with vomiting. Diagnosis in adults is frequently delayed; affected individuals experience repeated reactions before FPIES is considered. This delayed diagnosis can be attributed to poor awareness among the physicians and lack of the specific diagnostic criteria that accurately capture the adult FPIES presentation. Although the 2017 International Consensus Guidelines for FPIES proposed  diagnostic criteria, these criteria are more relevant to younger  patients experiencing FPIES, in whom repetitive vomiting is the cardinal feature. Since up to 40% of adults with FPIES do not experience vomiting, the 2017 Guidelines do not adequately capture this subset of patients. Thus, FPIES diagnosis should be considered for an adult patient who present with gastrointestinal symptoms within 1-4 hours following the specific food allergen ingestion on more than one occasion, with alternative etiologies carefully excluded. Future guidelines should highlight the differences between pediatric and adult patients and propose formal diagnostic criteria for adults.

A diagnosis of FPIES is usually made by clinical history and recognition of the symptoms pattern. However, a physician supervised  oral food challenge may be necessary to confirm the diagnosis, identify the offending food  or determine the natural resolution of FPIES. FPIES is a non-IgE mediated food allergy, thus percutaneous (prick) skin testing or IgE blood allergy testing is usually negative and not helpful for confirmation of FPIES diagnosis. However, in a subtype of FPIES known as atypical FPIES the patient  presents with classic symptoms consistent with FPIES and has positive skin and/or blood test to the FPIES trigger in question. In children, some of those with atypical FPIES may over time change (convert) to a classic food allergy with symptoms starting soon after food ingestion and involving skin and or lungs, in addition to gut. This conversion is more common in children who in addition to FPIES have other allergic disorders, including atopic dermatitis, asthma or other IgE-mediated food allergies. The risk of conversion from having an FPIES reaction to an IgE-mediated “immediate” reaction is not well known in adults.

Skin testing or blood testing to the FPIES food trigger will allow your practitioner to determine if you have “atypical” FPIES and  this will help determine how to approach the oral food challenge when the time comes to assess is FPIES has resolved with time.

Diagnosis and Testing

Diagnosis of FPIES in Children
Food Protein-Induced Enterocolitis Syndrome (FPIES) affects primarily young children, particularly during infancy with the early introduction of additional foods. FPIES is an abnormal immune response to an ingested food, resulting in gastrointestinal inflammation. The quantity of food that provokes symptoms has varied widely, reflecting the degree of hypersensitivity of individual patients. In some infants, the symptoms were provoked by very small food quantities, even traces of food that touched the mouth.


The symptoms of FPIES are primarily severe vomiting and diarrhea that can resemble acute gastrointestinal infection or food poisoning. The child may look very ill and dehydrated, resembling allergic anaphylactic shock or acute systemic infection.

The first episode usually occurs acutely within a couple of hours of ingestion but may be delayed for several hours, and it progresses rapidly in an alarming manner. A typical episode comprises repetitive projectile vomiting, pallor, followed by diarrhea, leading to lethargy and dehydration. Watery diarrhea follows in a few hours and may contain some blood. Rehydration results in rapid improvement though complete clinical resolution may take two to three days. In mild to moderate cases, frequent exposure to the causative food leads to chronic symptoms, irritability, and poor weight gain.

Causative Foods
Cow’s milk (or formula) and soy milk are the most common causes of FPIES in infants. In older children, rice, potato, and egg are the most common, but any food may cause FPIES.

The diagnosis of FPIES is based primarily on a convincing medical history of typical symptoms and progression, as described above, in the absence of fever or suspected food poisoning. Often, other possible causes of the symptoms are considered, including local or systemic infection, metabolic diseases, and gastrointestinal disorders. The causative food may not be identified until more than one episode happens.

Laboratory Findings
Laboratory tests are useful in evaluating the effects of the disease or in investigating for other diseases that can mimic FPIES. Acute episodes are associated with increased white blood cells, and the blood chemistry test may reflect dehydration or electrolyte imbalance. Chronic FPIES is associated with increased lymphocytes and eosinophils and sometimes decreased serum proteins. Typically, laboratory findings normalize and clinical improvement is seen within 48 hours of avoiding the causative food.

Unlike common allergic diseases, allergy skin tests or blood testing are not helpful because FPIES has a different underlying mechanism. Definite identification of the causative food would require performing titrated oral challenge with each suspected food. This test carries the risk of inducing an acute episode and should be planned and performed by an experienced specialist. The patient should be kept under observation for at least four hours. A blood cell count is drawn before the challenge and when symptoms appear or before discharge. For safety reasons, the test is usually avoided and the suspected foods are strictly eliminated. Recurrence of episodes would narrow down the causative food.

Once the culprit food is identified, strict avoidance should be followed. The result of accidental exposures might obviate the need for intentional challenge testing.

Provided by the I-FPIES Medical Advisory Board