A rise in the prevalence of rare phenotypic non-IgE-mediated gastrointestinal food allergies (non-IgE GIFAs) has occurred in Japan and it is way ahead of Western countries. Medical characteristics of non-IgE GIFAs vary between Western and Japanese patients. We explain this phenotype in this study since it is now recognised globally. A significant number of Japanese patients with non-IgE GIFAs present with vomiting and bloody diarrhoea, placing them between food protein-induced enterocolitis syndrome (FPIES) and food protein-induced allergic proctocolitis (FPIPA). Any neonates and young infants with non-IgE GIFAs who present with fever and elevated C-reactive protein have signs that are associated with serious systemic bacterial infections (e.g., sepsis). Any of these conditions are also classified as chronic FPIES under international standards. Eosinophils may be active in the reported inflammatory mechanism.

The phenotype found in Japan differs clinically from the classical phenotype in that it has higher amounts of eosinophils, indicating a ‘eosinophilic transition,’ as well as symptomatic variations, making it challenging to classify.

Reference: https://journals.lww.com/co-allergy/Abstract/2020/06000/Unique_features_of_non_IgE_mediated.14.aspx