Eosinophilic esophagitis (EoE) symptoms can be identical to those seen in acid reflux so there is no single sign or symptom that can reliably differentiate EoE from Gastroesophageal Reflux Disease (GERD). Therefore, confirming the diagnosis of EoE and ruling out acid reflux disease is the critical first step since treatment for GERD is much more straightforward. Furthermore, untreated reflux disease, like EoE, can also result in significant inflammation with eosinophils seen on biopsies taken during an upper endoscopy (EGD) due to acid from the stomach rising up or “refluxing” into the esophagus.
Complicating matters is that PPI-Responsible EoE has been recognized now as a new subtype of EoE. There is esophageal inflammation that can improve with PPIs e.g. omperazole (Prilosec), lansoprazole (Prevacid), esomeprazole (Nexium), etc, but is not thought to be caused by acid reflux.
One last point is that less common causes of esophageal eosinophilia should also be ruled out such as drug allergies, parasitic infection, or hypereosinophilic infections. Therefore your doctor should consider and evaluate when indicated for these other possible conditions.