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From time to time, we like to write about the rarer forms of food allergy. We’ve covered  Eosinophilic EsophagitisOral Allergy Syndrome, and allergies to red meat and water! Today’s blog topic will cover another lesser-known, but very serious food allergy: Food Protein-Induced Enterocolitis Syndrome (FPIES for short). 

What is it?

FPIES is a non-IgE immune system reaction to food that affects the gastrointestinal (GI) tract. IgE stands for the antibody immunoglobulin E, and most allergic reactions (think top eight most common food allergies) involve this antibody. FPIES is cell-mediated, which results in a delayed allergic reaction.

Notably, unlike typical food allergies, FPIES does not show up on standard allergy tests.

Who does it affect?

FPIES reactions often show up in the first weeks or months of a child’s life. Sometimes the child may be a little bit older if they’ve been exclusively breastfed. First reactions often occur when introducing solid foods, such as infant formulas or cereals, which are typically made with dairy or soy.

What are the common trigger foods?

For infants that experience FPIES from solid foods, rice and oats are the most common triggers. Other reported triggers include, but are not limited to: milk, soy, barley, sweet potato, squash, green beans, peas, and poultry. 

Any food protein can be a trigger and some infants may be sensitive to other foods as well. As with any food allergy, some children may only react to 1-2 foods, while others may react to several. 

What are the symptoms?

FPIES can cause severe symptoms following ingestion of a trigger food. Classic FPIES symptoms include diarrhea, severe vomiting, and dehydration. These can lead to changes in body temperature, blood pressure, and lethargy. Upon ingestion of a trigger food, there is a characteristic delay of 2-3 hours before the onset of symptoms. 

Symptoms can range from mild (such as an increase in reflux and several days of runny stools) to life-threatening (shock). In several cases, after repeated vomiting, children often begin to vomit bile. Diarrhea typically follows and can last up to several days. It’s important to note that each child is unique and may experience their own range and severity of symptoms. 

Importantly, many infants who are eventually diagnosed with FPIES are initially suspected to have a severe infection or sepsis based on their symptoms. 

How is it diagnosed?

FPIES cannot be detected with traditional allergy testing methods, such as skin prick or blood tests that measures IgE antibodies. It is accordingly tough to diagnose.

Researchers are currently looking to atopy patch testing (APT) for its effectiveness in diagnosing FPIES. APT involves placing the trigger food in a metal cap, which is left on the skin for around 48 hours. The skin is then observed for symptoms in the days following removal.

Additionally, the outcome of APT may determine if the child is a potential candidate for an oral food challenge: the gold standard for food allergy diagnosis. A medical doctor, often an allergist and/or gastroenterologist, should be involved in the diagnosis of FPIES.

Is there a silver lining?

The good news is that FPIES usually resolves with time! Many children outgrow FPIES by age 3, allowing kids to introduce the offending foods back into their diet over time. With proper medical attention and a personalized dietary plan, children with FPIES can grow and thrive! 

- Meg and the Allergy Amulet Team

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