Most people experience dry mouth (xerostomia) once in a while, such as when they are nervous, upset or under stress. This is temporary and goes away as soon as the person relaxes. Dry mouth can also be a sign of inadequate fluid intake, which can result in dehydration (loss of fluids from the body). Many gastrointestinal disorders including gastroenteritis and foodborne illness can also result in dehydration due to severe diarrhea and vomiting, which may cause dry mouth. Dehydration can be alleviated or avoided by drinking plenty of fluids, especially water.

Individuals can also experience dry mouth when the glands in their mouth that produce saliva, called salivary glands, become blocked, inflamed or malfunction. As a result, there may not be enough saliva to keep the mouth moist. For example, some infectious diseases caused by bacteria or viruses (e.g., mumps, parotitis) may cause temporary swelling of the salivary glands, resulting in dry mouth.

Other common factors that can affect the salivary glands and lead to chronic dry mouth include:

• Medications. Dry mouth is a common side effect of hundreds of drugs. Medications that may cause dry mouth include:
  
  
• • Gastrointestinal medications (e.g., antiemetics, antidiarrheals, antispasmodics, proton pump inhibitors). Medications used for treating many conditions affecting the digestive system, including nausea and vomiting, persistent diarrhea, abdominal cramping and excess stomach acid.
    
    
  • Antihistamines. Medications used to relieve or prevent allergy or allergy-like symptoms. They may also be used to treat sleeplessness, anxiety, motion sickness and other conditions.
    
    
  • Psychiatric medications (e.g., tricyclic antidepressants, antipsychotics). Prescription drugs used to control symptoms associated with many different types of mental illness, such as depression and psychosis.
    
    
  • Chemotherapy drugs. Medications used in the treatment of various forms of cancer including that of the digestive system.
    
    
  • Heart drugs (e.g., antiarrhythmics, antihypertensives, diuretics). Medications used for the treatment of heart conditions such as abnormal heart rhythms (beats), high blood pressure and heart failure.
    
    
  •  Illegal drugs (e.g., marijuana, methamphetamines)
    
     
• Chronic illnesses. Some diseases, especially if left untreated, can affect the salivary glands and result in persistent dry mouth. These include:
  
  
• • Diabetes mellitus. A disorder in the body’s ability to break down glucose (blood sugar).
    
    
  • Hypothyroidism. A condition in which the thyroid gland – located at the base of the neck – fails to produce enough thyroid hormone, which helps regulate body growth and metabolism.
    
    
  • Sarcoidosis. An inflammatory disease in which multiple small deposits of abnormal, non-cancerous tissue  called granulomas form in the liver, lungs, spleen and other organs.
    
    
  • Sjögren’s syndrome. An autoimmune disorder in which immune cells attack and destroy the glands that produce tears and saliva.
    
    
  • Kidney failure. The loss of the ability of the kidneys to excrete wastes, concentrate urine and conserve electrolytes. Patients with chronic kidney failure (such as those on dialysis) are usually on fluid-restricted diets, which can cause dry mouth.
    
    
  • Burning mouth syndrome. A disorder of unknown cause that involves a sensation of burning and pain in the tongue, gums, roof of the mouth, and cheeks. The condition is more common among postmenopausal women.
    
    
  • HIV/AIDS. Human immunodeficiency virus (HIV) is the virus that causes AIDS (acquired immune deficiency syndrome). This affects the body’s ability to fight infection. There is no cure and the disease is potentially fatal.
    
    
  • Alzheimer’s disease. A neurological condition causing loss of mental functions such as learning and memory.
    
    
  • Parkinson’s disease. A neurological condition causing tremors and problems with movement and speech.
    
    
• Stones and tumors in the salivary glands. The mouth can become dry when abnormal growths develop in the tubes (ducts) that lead from the salivary glands to the mouth. These lesions can block the flow of saliva.
  
  
• Nerve damage. Trauma to the head or neck from an injury or a surgical procedure may damage the nerves that prompt the salivary glands to produce saliva, resulting in dry mouth. Radiation therapy used in the treatment of cancer of the head, mouth or neck can also result in permanent dry mouth.
  
  
• Surgical removal of salivary glands.