Saliva plays many important roles: it lubricates and hydrates the mouth, facilitates speech, mastication and taste, and breaks down food for easier digestion.

A lack of saliva leads to cracked lips, more frequent bouts of cold sores (herpes labialis) and difficulty chewing and talking. It can also result in more cavities, bleeding gums, bad breath and a burning sensation. People who wear dentures may be particularly affected by dry mouth.

A dry mouth is not a result of age, but rather a side effect of medication (for instance, for high blood pressure, asthma, anxiety or depression). It can also be caused by radiotherapy or chemotherapy.