A method for treating or preventing disorders, diseases, and symptom of reflux, that is laryngopharyngeal reflux (LPR), in the laryngopharynx caused by pepsin comprises orally administering to the laryngopharynx of a patient an effective amount of cellulose powder. A method for treating or preventing damage to the lining membranes of at least some of the aerodigestive tract, the damage caused by pepsin, comprises coating at least some of the lining membranes with an effective amount of a cellulose powder. Upon inhalation of the powder, the powder coats the lining membranes. Upon coating the lining membranes, the powder becomes a gel. The gel prevents the pepsin from binding with the lining membranes, thereby preventing damage caused by pepsin in laryngopharyngeal reflux or in extra-esophageal reflux.