In this regard, the method used for differential diagnostic searches for suspected HI should include: (1) maintenance of a food diary for 2–4 weeks to identify a causal relationship between the occurrence of the corresponding symptomatology and the use of certain nutrients; (2) exclusion of food IgE-mediated allergies (skin prick test and specific IgE study), celiac disease (antibodies to gliadin, endomysia, and tissue transglutaminase), and inflammatory bowel diseases (analysis for calprotectin, colonoscopy). This evidence concerns the gene TGM2 and celiac disease.