FPIES (Food Protein-Induced Enterocolitis Syndrome)

What happens in FPIES

FPIES is a food allergy that does not involve IgE antibodies, the antibodies behind typical allergic reactions with hives and anaphylaxis. Instead, immune cells in the gut react to a food protein and trigger inflammation of the small and large intestine. This causes vomiting and fluid shifts that can lead to dehydration and low blood pressure.

Because IgE is not involved, skin prick tests and blood IgE tests are usually negative, and antihistamines and epinephrine do not help.

Symptoms

Acute FPIES

Happens when a food is eaten occasionally or after a break:

• repeated, forceful vomiting starting 1 to 4 hours after eating
• pallor, floppiness and lethargy
• diarrhea starting 5 to 10 hours later in some babies
• low body temperature
• low blood pressure and shock in about 15% of reactions

Symptoms usually settle within 24 hours once the food is out of the system. There are no hives, no swelling, and no wheeze.

Chronic FPIES

Happens when a trigger is eaten regularly, usually cow's milk or soy formula in young infants:

• intermittent vomiting
• chronic diarrhea, sometimes with blood or mucus
• poor weight gain
• irritability
• a severe acute reaction if the food is stopped and then reintroduced

Common trigger foods

Most children react to only one food, but some react to two or more. FPIES can also begin in adults, most often to shellfish.

FPIES vs typical food allergy

Diagnosis

FPIES is diagnosed from the history using international criteria, because there is no definitive test:

• repeated vomiting 1 to 4 hours after a suspect food without skin or breathing symptoms
• recurrent episodes with the same food
• improvement when the food is removed

It is often mistaken at first for a stomach virus or sepsis, especially after a first reaction. Blood tests during a reaction may show high white blood cell counts and changes in blood chemistry. An oral food challenge under medical supervision can confirm the diagnosis if the history is unclear, and later is used to check whether FPIES has resolved.

Treatment

Emergency treatment of a reaction

• IV fluids to correct dehydration and low blood pressure
• Ondansetron, an anti-vomiting medicine, given by injection or by mouth for milder reactions
• IV steroids sometimes for severe reactions
• observation for at least 4 to 6 hours

Families are given a written emergency letter explaining FPIES to ER staff, as it is often unfamiliar.

Long-term management

• strict avoidance of the trigger food
• for babies reacting to cow's milk or soy formula (distinct from the more common cow's milk protein allergy), an extensively hydrolyzed formula or, if needed, an amino acid formula
• breastfeeding can usually continue. Most breastfed babies tolerate their mother's diet
• introduce new foods one at a time with your allergist's guidance, often starting with lower-risk foods
• regular growth and nutrition checks, with a dietitian to avoid an unnecessarily restricted diet

Outlook

Most children outgrow FPIES. Milk and soy FPIES often resolve by around age 3 to 5. Grain and fish FPIES may last longer. Allergists usually offer a supervised food challenge every 12 to 18 months to check for tolerance. A small number of children develop IgE-mediated allergy to the same food later.

Frequently asked questions

What is FPIES?

FPIES is a delayed food allergy, mostly in infants, in which a trigger food causes repeated vomiting 1 to 4 hours after eating, often with pallor, floppiness and diarrhea. It is not IgE-mediated, so it does not cause hives and allergy tests are usually negative.

What are the most common FPIES trigger foods?

The most common triggers are cow's milk and soy in formula-fed infants, and rice and oats when solids are introduced. Egg, banana, avocado, sweet potato, chicken and fish are other triggers. Most children react to only one or two foods.

Is FPIES dangerous?

It can be. Severe reactions cause dehydration and low blood pressure, which need emergency IV fluids. With a diagnosis, avoidance of trigger foods and an emergency plan, children with FPIES do well and grow normally.

Do you use an EpiPen for FPIES?

No. Epinephrine is not effective for FPIES because it is not an IgE-mediated allergy. Reactions are treated with IV fluids and the anti-vomiting medicine ondansetron. Children with both FPIES and IgE allergy may still need epinephrine for the IgE allergy.

When do children outgrow FPIES?

Many children outgrow FPIES by age 3 to 5, especially milk and soy FPIES. Some grain and fish FPIES last longer. Allergists check for resolution with supervised food challenges, usually every 12 to 18 months.