FPIES is usually diagnosed through a careful history of the characteristic symptoms and exclusion of other similar disease states. Our allergist/immunologist and a gastroenterologist should be involved in making the diagnosis and treatment plan. Although Atopy Patch Testing (APT) is often used for FPIES patients, it is not a validated test for a FPIES diagnosis. The most definitive test is a medically supervised oral food challenge (OFC)-where the suspected food is given to the child in a controlled clinical environment.