Food protein-induced enterocolitis syndrome (FPIES) is a type of non-IgE-mediated food allergy that can be characterized by repeated vomiting not accompanied by IgE-mediated reactions, such as skin or respiratory symptoms, within 1-4 hours from the time of ingestion of the causative food product. Since the publication of the international consensus guidelines in 2017, reports on FPIES have increasingly been published by countries across the world. In most countries, the most frequent causative foods that cause FPIES include cow's milk, rice, fish, as well as hen's egg. In Japan, the incidence of FPIES caused by hen's egg, especially egg yolk, has been rapidly increasing since the last few years. Consequently, Japan has been leading the research on hen's egg-induced FPIES in terms of its epidemiological factors, such as age of onset and prognosis. However, much remains unknown about the causative antigens, route of sensitization, and vomiting and immunological mechanism. In addition, no established protocols are available for its diagnostic testing, safe and reliable oral food challenges, and long-term management. We hope to curb the increase in number of patients experiencing hen's egg-induced FPIES by clarifying these points in the future.