Food protein-induced enterocolitis syndrome (FPIES) is a rare food allergy. FPIES can occur in people of all ages, but it most commonly affects children and infants.

Unlike typical food allergies, FPIES only affects the gastrointestinal (GI) tract. It can cause severe vomiting, diarrhea, and stomach cramping. These symptoms typically show up within two hours of eating the food that triggers the allergy.

Food triggers for FPIES can be different from person to person. Any food can be a trigger, but some triggers are more common.

The most common FPIES triggers include:

FPIES is more likely to be seen in infants and young children. However, adults can still have an FPIES allergy or even develop one later in life.

FPIES is very rare. It’s so rare that researchers haven’t been able to estimate the number of people with the allergy. FPIES is difficult for doctors to diagnose. It’s possible many people will never receive a correct diagnosis. Children may even grow out of their allergy before a diagnosis is made.

According to the American College of Allergy, Asthma & Immunology (ACAAI), 40 to 80 percent of people with FPIES have a family history of allergic diseases. Allergic diseases may include:

The first symptoms of FPIES often show up at a very early age. Children and infants may begin to show signs of FPIES when they first begin drinking formula, taking breast milk, or eating solid foods.

Any time a new food is introduced, an infant can experience an allergy to it. In adults who develop FPIES, the symptoms may begin at any point in life.

The symptoms of FPIES include:

The symptoms of FPIES are easily confused with those of stomach viruses, food poisoning, and other viral or bacterial infections.

In extreme cases, people with FPIES reactions may have to be hospitalized for treatment. Rehydration with intravenous (IV) fluids may be necessary if the allergic episode is severe.

For children, FPIES symptoms can ultimately lead to failure to thrive. This condition can stunt their overall growth and development. That’s why receiving a proper diagnosis and management are vital.

Although it’s a food allergy, FPIES isn’t diagnosable with a typical skin prick or blood test. These two tests are usually used to diagnose a food allergy. They detect reactions to a variety of triggers, including foods.

Because an FPIES reaction is contained to your GI tract and doesn’t involve antibodies, these two tests won’t work. You must consume or eat the food in order to trigger symptoms.

For that reason, your doctor may conduct an oral food challenge. To do this, you’ll consume a small amount of the possible trigger under your doctor’s supervision. You’ll be monitored for the signs and symptoms of an FPIES reaction. If you have a reaction, this may be the confirmation your doctor needs for an FPIES diagnosis.

FPIES has no treatment or cure. The best practice is strict avoidance of the trigger foods.

If your infant is allergic to milk or formula, your doctor will work with you to find an allergy-friendly formula or one designed for sensitive stomachs.

If the trigger is just one or a few foods, avoiding those foods will prevent an allergic episode. If the number of triggers is high, you may need to work with your doctor and dietitian to create a diet that’s healthy, nutritious, and also safe for your allergy.

The outlook for people with FPIES differs based on their age at the time of diagnosis. Children often outgrow their food allergies by age 3 or 4. If an FPIES allergy lasts into older childhood or even adulthood, the likelihood that you’ll outgrow the allergy is smaller. Adults who develop the allergy later in life rarely outgrow it.

The symptoms of FPIES may resemble those of other conditions and infections. That’s what makes it so difficult to diagnose.

If you that notice symptoms are chronic or occur after you or your child eat certain foods, talk with your doctor. Start a conversation about food allergies with them. You may find the answers you need.

Your doctor may refer you to an allergist in order to confirm a diagnosis, too.