A man developed a type of food allergy called FPIES after receiving a stem cell transplant. This is believed to be the first reported instance of peanut-induced FPIES in a transplant patient.
FPIES stands for food protein-induced enterocolitis syndrome. It’s a food allergy that primarily involves the gut. Unlike IgE-mediated food allergies, which cause immediate skin or airway reactions, FPIES symptoms are delayed. Symptoms typically begin a few hours after consuming the trigger food and can include severe vomiting, diarrhea and dehydration. Other symptoms can include looking pale or weak and potentially, low blood pressure.
Severe cases can send people to the emergency room. Children with undiagnosed FPIES may have poor weight gain or a failure to thrive.
The 66-year-old man underwent a stem cell transplant from an unrelated donor to treat a type of blood cancer. In a stem cell transplant, a patient’s bone marrow and the cancerous stem cells within it are first intentionally wiped out with high-dose chemotherapy. The patient then receives healthy stem cells from a donor. These travel to the bone marrow, engraft, and start producing normal blood cells.
The patient had a lifelong tolerance to peanut butter and enjoyed it regularly, says lead study author Dr. Bushra Tbakhi, an allergy and immunology fellow at the University of Cincinnati.
About three months after his transplant, the man became nauseous, lethargic and vomited profusely after eating a peanut butter sandwich. His reaction occurred about three hours after the meal.
Two weeks later, he had an identical reaction several hours after eating peanut butter.
FPIES Triggers in Kids Vs. Adults
Since FPIES doesn’t involve IgE antibodies, allergy skin and blood tests are usually negative for elevated IgE. That was the case for this patient.
He had skin and blood component tests for peanut allergy, which came back negative. This confirmed that the reaction was not IgE-mediated, Tbakhi says. “The timing and reproducibility of the reactions … are highly consistent with an FPIES to peanut,” Tbakhi says.
In children, the most common FPIES triggers are dairy, soy, or grains like rice and oats, although any food can cause FPIES symptoms. A 2019 study found about 0.5 percent of American children under age 18 had an FPIES diagnosis.
Although the condition is most often seen in infants and young children, adults can develop it. Shellfish is the most common trigger food. Finned fish, dairy, eggs, and wheat and other foods have also been reported as triggers.
Adults who develop FPIES often tolerate the foods for years before they develop the condition.
The reason why the man developed FPIES after the stem cell transplant isn’t known. But he was taking immunosuppressant drugs that may increase intestinal permeability and promote sensitization to food allergens, Tbakhi says.
The study was presented at the 2025 American College of Allergy, Asthma & Immunology (ACAAI) Annual Scientific Meeting in Orlando in November 2025.
Related Reading:
All about FPIES (Food Protein-Induced Enterocolitis Syndrome)
Lung Transplant Transfers Food Allergy
