FPIES in Adults: A lesser known food hypersensitivity reaction

FPIES in Adults: A Hidden Food Hypersensitivity You Should Know About

When most people think of food allergies, they picture hives, throat swelling, or anaphylaxis. But there's a lesser-known type of food allergy that looks nothing like the classic picture — and it's increasingly being recognized in adults.

What Is FPIES?

Food Protein-Induced Enterocolitis Syndrome, or FPIES, is a non-IgE-mediated food allergy. Unlike typical allergic reactions, FPIES doesn't cause skin rashes or breathing problems. Instead, it targets the gut, triggering severe gastrointestinal symptoms — usually one to four hours after eating a trigger food. Historically considered a childhood condition that most kids outgrow by age three or four, researchers now recognize that FPIES can develop for the first time in adulthood.

What Does Adult FPIES Look Like?

The hallmark symptoms in adults include intense abdominal pain, diarrhea, nausea, abdominal distention, and sometimes repetitive vomiting. These episodes can be severe enough to cause dehydration and even lead to emergency room visits. Recent imaging studies have shown that during an FPIES reaction, the small intestine can become significantly dilated and swollen — helping explain the severe bloating many patients experience.

Adult FPIES looks somewhat different from the pediatric version. Abdominal pain and diarrhea tend to dominate in adults, while vomiting is the primary symptom in children. There is also a striking female predominance in adult cases, with women making up over 90% of patients in some studies.

What Triggers It?

In adults, seafood — including fish, shellfish, and mollusks — is the most common trigger, which is a notable contrast to childhood FPIES, where cow's milk and grains are the usual culprits. Egg, wheat, and cow's milk can also cause adult-onset FPIES, and many patients react to more than one food group.

The Diagnostic Challenge

FPIES is notoriously difficult to diagnose. Standard allergy tests like skin prick tests and blood IgE levels are typically negative, since FPIES isn't driven by IgE antibodies. The gold standard for diagnosis is a supervised oral food challenge, where a patient eats the suspected trigger food under medical observation. Because symptoms mimic many other conditions — food poisoning, irritable bowel syndrome, inflammatory bowel disease — patients often go years before receiving the correct diagnosis.

Living with Adult FPIES

The primary treatment is strict avoidance of trigger foods. During acute reactions, IV fluids and the anti-nausea medication ondansetron can help. Unlike childhood FPIES, adult FPIES tends to persist: in one long-term study, only about 17% of adults achieved tolerance after a median of 3.5 years. Adults with FPIES also appear to have higher rates of other gastrointestinal conditions, including irritable bowel syndrome and eosinophilic esophagitis.

If you experience unexplained, recurring episodes of severe GI symptoms hours after eating — especially seafood — talk to an allergist. FPIES may be rare, but awareness is the first step toward diagnosis. Get an expert consultation with Dr. Sandra Ho at Avant Allergy in Los Angeles.