Trial to Assess the Effects of an Antimicrobial Mouthwash on the Esophageal Microbiome

Inclusion Criteria: * Age \>18 * Scheduled for upper endoscopy for clinical indications * No allergy or other contraindication to chlorhexidine Exclusion Criteria: * Use of proton pump inhibitors or H2 receptor antagonists within 1 month of enrollment. Acid suppressant medications raise the gastric pH and can dramatically alter the gastric and esophageal microbiome. * History of upper gastrointestinal cancer * History of histologically proven Barrett's esophagus * History of antireflux or bariatric surgery, or other gastric or esophageal surgery * Use of antimicrobial mouthwash within 1 month of enrollment * Use of antibiotics or immunosuppressant medications within 3 months of enrollment * Use of steroid inhalers or nasal sprays within 1 month of enrollment * HIV or other immunosuppressed states or conditions (e.g. active malignancy) * Pregnant or breast feeding * Inability to give informed consent