Two Pediatric Cases of Food Protein-Induced Enterocolitis Syndrome to Soy Eaten as an Infant Food

Food protein-induced enterocolitis syndrome (FPIES) is a non-IgE-mediated food allergy that can be caused not only by infant formula but also by infant food. Herein, we report two pediatric cases of FPIES to solid soy foods, such as tofu. The patients presented with repetitive vomiting after eating the trigger food as infant food. Although both cases promptly recovered following the cessation of the trigger food, one case required rapid intravenous hydration for compensated shock. Both cases were diagnosed with FPIES to soy based on the typical presentation and parental interviews regarding food exposure. One case had a positive response to an oral food challenge for tofu, and both cases were negative for soy-specific IgE. One of our cases did not develop FPIES from fermented soy products despite having soy-triggered FPIES. The fermentation process may reduce the allergenicity of soy, but further evidence is required to confirm this hypothesis. There are various trigger foods for solid food FPIES (SFF), and these differ among countries. Solid food FPIES to soy is more common in Japan than in other countries due to the frequent use of tofu in infant food. Increased international awareness of the possibility of tofu-triggered FPIES may be warranted due to the rising global use of tofu in infant food.