Food Protein-Induced Enterocolitis Syndrome (FPIES)

What happens in FPIES

FPIES is a non-IgE mediated food allergy. Unlike a typical food allergy, where IgE antibodies trigger hives, swelling and breathing trouble within minutes, FPIES involves other parts of the immune system (T cells and inflammatory chemicals) acting on the gut lining. The reaction is delayed and confined mainly to the digestive tract, but it can cause severe fluid shifts and shock.

FPIES usually starts in the first year of life, often when a baby first has formula or starts solid foods. It is thought to be more common than once believed, but it is often misdiagnosed as a stomach virus (gastroenteritis), sepsis or a surgical emergency.

Symptoms

Acute FPIES (after occasional exposure)

• repeated, forceful vomiting beginning 1 to 4 hours after eating the trigger, often many times
• pallor (pale or gray skin)
• lethargy or floppiness
• diarrhea 5 to 10 hours after the food in some children
• low body temperature and low blood pressure in severe reactions
• recovery within about 24 hours once the trigger is cleared

Notably absent are hives, itching, lip swelling, wheezing and coughing, which suggest an IgE allergy instead.

Chronic FPIES (with regular exposure)

Seen in young infants fed a trigger every day, usually cow's milk or soy formula:

• intermittent vomiting
• chronic watery diarrhea, sometimes with blood or mucus
• poor weight gain or weight loss (failure to thrive)
• improvement within days of removing the food, with an acute reaction if it is reintroduced later

Common trigger foods

Most children react to one food, but some react to several. Breastfed babies rarely react through breast milk, and breastfeeding is usually continued.

FPIES vs typical food allergy

Diagnosis

FPIES is diagnosed clinically using international consensus criteria. Doctors look for:

• vomiting 1 to 4 hours after a suspected food, without typical allergy symptoms
• plus additional features such as repeated reactions to the same food, pallor, lethargy, need for an ER visit or IV fluids, or diarrhea

Tests may be used to exclude other causes such as infection, metabolic disorders and bowel obstruction. Allergy tests are not useful for diagnosing FPIES, though they may be checked because some children also develop IgE allergy. When the diagnosis is uncertain, an allergist may perform a supervised oral food challenge in hospital with IV access.

Treatment

Emergency treatment of a reaction

• IV fluids to treat dehydration and shock
• ondansetron (an anti-sickness medicine), which can stop vomiting
• IV steroids sometimes for severe reactions
• observation until the child is drinking and alert

Epinephrine auto-injectors are not routinely prescribed for FPIES because the reaction is not IgE-mediated, unless the child also has an IgE food allergy.

Families should carry a written FPIES emergency letter explaining the condition to ER staff, because it is not widely recognized.

Long-term management

• strict avoidance of the trigger food
• hypoallergenic formula (extensively hydrolyzed or amino acid-based) for infants with milk or soy FPIES. Babies with other forms of milk protein allergy are managed in a similar way
• introducing new foods one at a time, starting with lower-risk foods, in small amounts, at home in the morning so reactions can be observed. Your allergist will guide the order
• dietitian support to keep nutrition balanced while avoiding triggers
• follow-up every 12 to 18 months to consider a supervised food challenge

Outlook

Most children outgrow FPIES. Milk and soy FPIES often resolve by age 3 to 5, while solid food triggers such as rice, oat and fish may take longer. FPIES that starts in older children or adults, typically to shellfish or fish, tends to persist.

Frequently asked questions

What is FPIES?

FPIES, or food protein-induced enterocolitis syndrome, is a delayed food allergy affecting the digestive system, mainly in infants. About 1 to 4 hours after eating a trigger food, the child vomits repeatedly, becomes pale and lethargic, and may later have diarrhea.

What are the most common FPIES trigger foods?

In the US, cow's milk and soy are the most common triggers. Common solid food triggers include rice, oat, egg and barley. Others include sweet potato, banana, poultry and fish. Most children react to only one or two foods.

How is FPIES different from a regular food allergy?

FPIES reactions are delayed by hours, affect mainly the gut, and do not cause hives or breathing problems. Standard allergy tests are usually negative. Treatment for a reaction is IV fluids and anti-sickness medicine rather than epinephrine.

How is an FPIES reaction treated?

Mild reactions may settle with oral fluids at home under medical guidance. Moderate or severe reactions need emergency care with IV fluids and ondansetron. Families should carry an emergency letter from their allergist explaining the diagnosis.

Do children outgrow FPIES?

Most do. Many children outgrow milk and soy FPIES by age 3 to 5, and solid food FPIES often resolves later in childhood. An allergist will decide when it is safe to test for tolerance with a supervised food challenge.