Xerostomia, a condition commonly known as "Dry Mouth" occurs when the saliva in your mouth becomes diminshed. Your saliva contains proteins and enymes which keep your mouth lubricated and healthy. It flushes away bacteria, reduces bad breath, helps to prevent infections, and aids in digestion. Conversely, when you do not have enough saliva, food and bacteria can stick to your teeth. This causes plaque build-up which can lead to cavities, mouth infections and other oral health problems.
About 1 out of very 4 adults have a dry mouth condition. The number one cause is medications (both prescription and non-prescription.) Other conditions such as cancer, diabetes, and depression can also cause dry mouth.
While you can get immediate relief by simply sipping water, this will not lubricate and protect your mouth in the same way that saliva does. There are special rinses that you can use that do a better job of protecting your mouth such as Biotene. I also recommend a fluoride rinse to help guard against tooth decay.