Xerostomia (Chronic Dry Mouth)

How saliva works and what goes wrong

You produce about 0.5 to 1.5 liters of saliva a day from three pairs of major glands (parotid, submandibular and sublingual) and hundreds of minor glands in the lips and cheeks. Saliva lubricates, buffers acid, remineralizes enamel, fights microbes and helps with taste, chewing and swallowing.

Xerostomia arises when:

• the glands are damaged: by autoimmune attack (Sjogren's), radiation, infection or surgery
• the nerve signals to the glands are blocked: by anticholinergic and other medicines, or nerve injury
• the body lacks fluid: dehydration, uncontrolled diabetes, kidney disease
• saliva evaporates faster: mouth breathing, CPAP without humidification

Some people feel dry with normal saliva flow, for example with anxiety or burning mouth syndrome. That is why doctors measure flow in persistent cases.

Causes of xerostomia

Medicines

Hundreds of medicines reduce saliva. The risk rises with the number taken. Anticholinergics, tricyclic antidepressants, antihistamines, antipsychotics, diuretics, opioids, and bladder medicines are the strongest offenders.

Sjogren's syndrome

Sjogren's syndrome is an autoimmune disease in which white blood cells attack the moisture-producing glands. It causes dry mouth and dry eyes, and often fatigue, joint pain and swollen parotid glands. About 9 in 10 patients are women, usually diagnosed in their 40s or 50s. It can occur alone or with rheumatoid arthritis or lupus.

Head and neck cancer treatment

Radiation that passes through the salivary glands often causes severe, long-lasting xerostomia. Modern techniques such as IMRT spare glands where possible. Radioactive iodine for thyroid cancer and some chemotherapy can also reduce saliva.

Other causes

• Diabetes, especially when poorly controlled
• HIV, hepatitis C, and IgG4-related disease affecting the glands
• Salivary stones and gland infections (usually one gland)
• Graft-versus-host disease after stem cell transplant
• Dehydration, kidney failure and dialysis fluid limits

Complications

Tooth decay can progress strikingly fast. Some people lose several teeth within a year or two after radiation without preventive care.

How xerostomia is diagnosed

1. History: onset, medicines, dry eyes, thirst, urination, radiation history, joint symptoms.
2. Examination: a dry, sticky or fissured tongue, frothy or no pooled saliva, a mirror sticking to the cheek, cavities, thrush and gland swelling.
3. Sialometry: collecting and measuring saliva over 5 to 15 minutes. Unstimulated flow under 0.1 ml per minute indicates hyposalivation.
4. Blood tests: glucose and HbA1c, anti-SSA (Ro) and anti-SSB (La) antibodies, ANA, rheumatoid factor, and kidney function.
5. Imaging: ultrasound of the salivary glands, sometimes MRI or sialography.
6. Lip biopsy: a small sample of minor salivary glands from inside the lower lip to confirm Sjogren's.

Treatment

Treat or reduce the cause

• Review all medicines with your doctor or pharmacist. Switching to an alternative, reducing the dose, or taking a medicine in the morning instead of at night often helps.
• Control blood sugar.
• Treat nasal blockage and use humidified CPAP.

Saliva substitutes and stimulants

• Saliva substitutes: sprays, gels and rinses containing carboxymethylcellulose, xanthan gum or similar. They relieve symptoms for a short time and are used as often as needed.
• Chewing and lozenges: sugar-free gum and xylitol lozenges stimulate remaining glands.
• Prescription sialagogues: pilocarpine and cevimeline stimulate saliva when some gland function remains. They are used for Sjogren's and after radiation. Side effects include sweating, flushing and frequent urination, and they are avoided in uncontrolled asthma and some eye conditions.

Dental protection

• 5,000 ppm fluoride toothpaste, fluoride varnish or custom fluoride trays
• Dental visits every 3 to 4 months
• Limit sugary and acidic foods and drinks, especially between meals
• Remove dentures overnight and clean them daily
• Prompt treatment of thrush with antifungal medicine

For radiation-related xerostomia

Some centers use amifostine during radiation to protect the glands, or submandibular gland transfer surgery before treatment. Acupuncture-like nerve stimulation has shown benefit in some studies. Hyperbaric oxygen and gene therapy are being researched.

Living with chronic dry mouth

• Carry water and sip often, especially while talking and eating.
• Moisten food with sauces, soups and gravies. Avoid dry crackers and crumbly foods.
• Use a bedside humidifier and a gel substitute at night.
• Use alcohol-free mouthwash and lip moisturizer.
• Treat associated dry eyes if you have Sjogren's.

For everyday causes and quick relief tips, see dry mouth.

Frequently asked questions

What is xerostomia?

Xerostomia is the medical term for the feeling of a dry mouth. It is usually caused by reduced saliva production, called hyposalivation. Common causes are medicines, Sjogren's syndrome, radiation to the head and neck, and diabetes.

Is xerostomia permanent?

It depends on the cause. Medicine-related and dehydration-related dry mouth usually reverses once the cause is corrected. Dryness after head and neck radiation often lasts years and may be permanent, though it can improve partly over 1 to 2 years. Sjogren's syndrome is a lifelong condition.

What is the best treatment for xerostomia?

The best treatment fixes the cause, such as changing a medicine. Otherwise, saliva substitutes, sugar-free gum and xylitol lozenges relieve symptoms, and pilocarpine or cevimeline can stimulate saliva. High-fluoride toothpaste and frequent dental checks are essential to prevent decay.

How is xerostomia different from dehydration?

Dehydration is a whole-body lack of fluid, which causes dry mouth along with thirst, dark urine and tiredness, and corrects quickly with fluids. Xerostomia is persistent dryness of the mouth that continues even when you drink normally, usually from gland damage or medicines.

Can xerostomia be a sign of Sjogren's syndrome?

Yes. Dry mouth together with dry, gritty eyes, especially in a woman in her 40s or 50s, is a classic sign of Sjogren's syndrome. Fatigue, joint pain and swollen glands are also common. Antibody blood tests and sometimes a lip biopsy confirm the diagnosis.