hello thank you for trusting HCM dear most common cause for dry mouth is infections like pharyngitis or GERD or mouth Wash or medications etc.. avoid antihistamine and anti cholinergic drugs, drink plenty of water.if your in a dry environment use humidifier.use salt water gargling.use vit a and zinc tablets still symptoms persistent please consult your ent surgeon he will examine and treat you accordingly. I think I answered to your question if you have more questions feel free to ask. take care