Ask the Doctors

Dear Doctor: After suffering from a metallic taste in my mouth for two years, I've been told by my doctor that I might be suffering from burning mouth syndrome. What can you tell me about this? I'm past menopause, take blood pressure medication, have had numerous X-rays and am pre-diabetic, all of which an internet search suggested might be factors.

Dear Reader: Burning mouth syndrome is a poorly understood chronic condition that leads -- just as the name says -- to a burning sensation within the mouth. The sensation occurs without any visible changes -- no lesions, no redness, just pain. The rate of the disease varies widely, but it appears to occur in about 1 in 1,000 people. The syndrome is rare in people under 30 and is most prevalent in those ages 60 to 80. Women are more afflicted than men by a ratio of 5-to-1.

Multiple theories have been proposed about the syndrome's cause, with a dysfunction of nerves that lead to the mouth being the most likely reason. These nerves fire abnormally, giving the sensation of pain even when there's no trauma to create pain. But then, the brain itself may play a role, possibly altering the sensory input received from the mouth. Also supporting a brain connection is the fact that the syndrome is frequently associated with stressful life events, sleep disorders, anxiety and depression.

Regardless, the pain is described as a scalding sensation, accompanied by tingling, numbness and a feeling of dryness in the mouth. A bitter or metallic taste (like you are experiencing) is noted in two-thirds of patients. The tongue is the most common area involved, but the pain can occur anywhere in the mouth, including the lips.

The syndrome is characterized by how often the symptoms occur. For 10 percent of people, the symptoms occur every few days; 35 percent of people experience the symptoms daily, but find them worse in the evening and reduced or absent in the morning; 55 percent of people have symptoms all day long.

As you have done, it is important to rule out specific causes for the burning sensation in the mouth. Vitamin deficiencies, diabetes, autoimmune conditions and certain types of chemotherapy or radiation can lead to mouth-related nerve damage. Infections, the antidepressant paroxetine and ACE inhibitors used for blood pressure can all cause mouth pain.

Treating the syndrome can be difficult. Topical medications such as capsaicin (from chili peppers), clonazepam, lidocaine and doxepin can deaden the nerve stimuli in the area of pain. In small studies, the antioxidant alpha-lipoic acid has shown benefit in 35 to 70 percent of people with the syndrome when taken at 600 milligrams per day.

Because of the psychological issues often associated with burning mouth syndrome, cognitive behavioral therapy can be effective in reducing pain, as can antidepressants -- SSRIs, SNRIs and tricyclic drugs, like amitriptyline. Drugs used for nerve pain, including gabapentin and pregabalin (Lyrica), may also help.

Unfortunately, burning mouth syndrome can last for months to years, with many people having some degree of symptoms even after five years. So it's best not to simply hope that it will go away. Severe symptoms warrant the use of a topical medication, alpha-lipoic acid, cognitive behavioral therapy or even oral medications.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

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