Dry mouth, also known as xerostomia, is fairly common. Most people have dry mouth once in a while, such as when they are nervous, upset or under stress. Dry mouth may also indicate inadequate fluid intake, which can result in dehydration (loss of fluids from the body).

In most cases, xerostomia can be relieved simply by drinking plenty of fluids, especially water. However, persistent dry mouth may a sign of an underlying illness, such as diabetes, that requires medical treatment.

The mouth contains three major pairs of salivary glands. The parotid glands, located just behind the angle of the jaw (below and in front of the ears) are the largest. Deep inside the mouth, lie two smaller pairs called the sublingual and submandibular glands. In addition to these major glands, various tiny salivary glands are distributed throughout the mouth. All together, the salivary glands produce about 3 pints of saliva per day in the average adult.

Saliva is a fluid composed of water, electrolytes, mucus and enzymes, and is secreted by tiny ducts (openings) in the salivary glands. It lubricates and helps keep the mouth clean by reducing damaging acids in the mouth and by controlling bacterial growth that can dissolve tooth enamel or lead to mouth infections. Saliva also helps people taste and swallow foods and serves an important function of the digestive system – it breaks down food for digestion. The volume and type of saliva secretion is controlled by the autonomic nervous system (the part of the nervous system – composed of the brain, spinal cord and nerves – that controls involuntary body functions).

When there is a blockage, inflammation or malfunction of the salivary glands, the production and flow of saliva can be affected. Secretion of saliva can decrease substantially and become almost nonexistent. As a result, the mouth can feel excessively dry.

Most elderly people often experience dry mouth. However, it is not a normal part of aging. Dry mouth occurring in elderly patients is usually related to the use of certain medications (e.g., hypertension drugs) that cause this side effect.

Chronic dry mouth can interfere with tasting, chewing, swallowing, speaking and even wearing dentures. It can also result in bad breath and increase the risk of tooth decay (dental cavities) and gum disease (inflammation and infection of the tissues and bone that support the teeth) due to the accumulation of bacteria in the mouth.