Dry mouth is caused by a reduced or absent flow of saliva. This condition can cause discomfort, interfere with speech and swallowing, make wearing dentures difficult, cause bad breath (halitosis), and worsen oral hygiene by causing a decrease in the acidity of the mouth and an increase in bacterial growth, which contributes to the development of cavities. Longstanding dry mouth can result in severe tooth decay and candidiasis of the mouth. Dry mouth is a common complaint among older adults.
Causes of Dry Mouth
Dry mouth occurs when the salivary glands (glands in the mouth that produce saliva) malfunction and thus decrease saliva production. There are many causes, including dehydration and mouth breathing (see table Some Causes of Dry Mouth).
The most common causes of dry mouth are
Medications and other substances
Radiation to the head and neck (for cancer treatment)
Medications are the most common cause overall. About 400 prescription medications and many nonprescription (over-the-counter) medications cause a decrease in saliva production. The most common classes of medications include the following:
Medications that have anticholinergic effects (those that block acetylcholine)
Antiparkinsonian medications (those used to treat Parkinson disease)
Cancer chemotherapy medications
Many commonly used medications have anticholinergic effects. Dry mouth is only one among many anticholinergic side effects.
Many chemotherapy medications cause severe dryness and mouth sores (stomatitis) while they are being taken. These problems usually end after the medications are stopped.
Other common medications that cause dry mouth include certain antihypertensives (medications used to lower high blood pressure), antianxiety medications (used to treat anxiety disorders), and antidepressants (used to treat depression).
Tobacco use usually causes a decrease of saliva.
Radiation therapy for head and neck cancer can severely damage the salivary glands, often causing permanent dryness. Even low doses of radiation can cause temporary drying.
Less common causes of dry mouth include bodywide (systemic) disorders. Dry mouth is very common among people with Sjögren syndrome. Some people with diabetes or HIV infection have problems with dry mouth.
Evaluation of Dry Mouth
Not all people with a dry mouth need to be immediately evaluated by a doctor. The following information can help people decide whether a doctor’s evaluation is needed and help them know what to expect during the evaluation.
Warning signs
In people with dry mouth, certain symptoms and characteristics are cause for concern. They include
Extensive tooth decay
Dry eyes, dry skin, rash, or joint pain
When to see a doctor
People who have warning signs should see a doctor right away. People with extensive tooth decay should have a dental examination. People with a dry mouth but no warning signs and who otherwise feel well may see their doctor within a week or so.
What the doctor does
Doctors first ask questions about the person’s symptoms and medical history. Symptoms of dry or irritated eyes, dry skin, rash, and/or joint pain raise the possibility of Sjögren syndrome. Doctors also ask about a history of past or current radiation treatment, head and neck trauma, and a diagnosis of or risk factors for HIV infection. Doctors need to know all the medications a person is taking or substances being used to find out whether any are causing the dry mouth.
Doctors then do a physical examination. The physical examination is focused on the mouth, to see the degree of dryness. If the degree of dryness is unclear, doctors can hold a tongue depressor against the inside of the cheek for 10 seconds. If the tongue depressor falls off immediately when released, the flow of saliva is considered normal. If there is difficulty removing the tongue depressor, the flow of saliva is not normal. The lipstick sign, where lipstick sticks to the front teeth, may be a useful indicator of dry mouth.
Doctors also examine the mouth for the presence of any sores caused by the fungus Candida albicans and check the condition of the teeth (for instance, whether there are any cavities in unusual places). Unexpectedly severe and rapid tooth decay may be a sign of recreational and illicit drug use, particularly methamphetamines.
What doctors find during the history and physical examination often suggests a cause of the dry mouth (see table Some Causes of Dry Mouth) and the tests that may need to be done. If the dry mouth began shortly after a new medication was started, doctors often try stopping the medication to see whether symptoms go away.
Testing
Sometimes, doctors test how well the salivary glands are functioning by measuring the flow of saliva (a test called sialometry). People chew paraffin or apply citric acid to the tongue to stimulate the flow of saliva, and then doctors collect the saliva. Measuring the flow of saliva can help doctors determine whether the dry mouth is getting better or worse.
If doctors are unable to determine the cause of dry mouth, people should usually undergo a biopsy (removal of a sample of tissue for examination under a microscope) of a minor salivary gland on the lower lip to detect Sjögren syndrome, sarcoidosis, amyloidosis, tuberculosis, or cancer. They may also consider HIV testing.
Treatment of Dry Mouth
Treatment of the cause, including stopping causative medications when possible
Sometimes medications to increase saliva production
Saliva substitutes
Regular oral hygiene and dental care
When possible, the cause of dry mouth is treated. For people with medication-related dry mouth whose current medications cannot be stopped or changed, medications should be taken in the morning rather than at night, because nighttime dry mouth is more likely to cause cavities
Symptom control
Treatment that helps control the symptoms of dry mouth consists of measures that
Increase existing saliva
Replace saliva with other liquid
Control cavities
Petroleum jelly can be applied to the lips and under dentures to relieve drying, cracking, soreness, and trauma of the lining of the mouth. A cold-air humidifier may aid mouth breathers, who typically have their worst symptoms at night.
People should avoid sugary or acidic foods and beverages and any irritating foods that are dry, spicy, or excessively hot or cold. People should especially avoid sugar near bedtime.
Essentials for Older Adults: Dry Mouth
Dry mouth is more common among older adults, but this is probably due to the many medications typically used by older adults rather than to aging itself.
Key Points
Medications are the most common cause, but some diseases (most commonly Sjögren syndrome or HIV infection) and radiation therapy can also cause dry mouth.
Because people with dry mouth are at high risk of tooth decay, meticulous oral hygiene, additional preventive measures at home (including daily use of over-the-counter fluoride rinses or dentist-prescribed fluoride toothpaste), and dentist-applied fluoride are essential.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
MouthHealthy.org: Provides information on oral health, including nutrition and guidance on selecting products that carry the American Dental Association's seal of approval. There is also advice on finding a dentist and how and when to see one.
