Xerostomia, or dry mouth, is the unnatural dryness of mouth. Sometimes the amount of saliva in the mouth gets decreased unnaturally, resulting in the dryness. The saliva in the mouth is essential for chewing, swallowing and digestion of food. Also, it helps in preventing tooth decay and bacterial or fungal infection in the mouth. It is not a severe medical condition and is commonly found in older people, above 65 years of age.