Therefore, the aim of this research was to analyze the impact of CYP2C19 and STAT6 genetic variation (and variation in other relevant pharmacogenes such as CYP3A4, CYP3A5, or ABCB1) on PPI response, and of STAT6 variants on EoE baseline status (i.e., peak eosinophils count, endoscopic phenotype, and symptoms) and comorbidities. This evidence concerns the gene CYP3A4 and eosinophilic esophagitis.