DEAR DOCTOR K:

For months, my mouth has been painfully burning and tingling. What could be causing my symptoms? Are there any treatments for it?

DEAR READER:

Several conditions can cause a burning sensation in the mouth. Some nutritional deficiencies -- particularly of B vitamins, iron and zinc -- can cause it. These problems can be detected by simple blood tests.

Medicines that cause the mouth to become dry (due to decreased saliva production) can result in mouth irritation. There are too many of these medicines to list here, but check a reliable website that provides information about drugs and their side effects.

Sometimes a person can develop an allergy to dentures and related adhesive creams, toothpastes or mouthwashes that produce irritation of the tissues of the mouth. You can experiment by seeing what happens when you stop using one of these potential allergy triggers (and substituting a different brand).

Conditions that damage small nerves, such as diabetes, can cause mouth pain. So can mouth infections, particularly with fungus (yeast).

There also is a condition called burning mouth syndrome (BMS) that produces a burning -- sometimes scalding -- sensation on the lips and tongue and throughout the mouth. In BMS, the pain is present for at least some part of every day, the tissues of the mouth look normal (not irritated or inflamed) to the doctor or dentist, and the conditions I have mentioned already are not present.

Doctors don't know what causes BMS. Some think it is a psychiatric condition, but I'm dubious about that. I think that when doctors don't understand the cause of a person's symptoms, we sometimes think (and say to our patient) that the symptoms are just imaginary. That may make us feel better, but it doesn't make the patient feel so great. And if there really is a problem that we're ignoring, we have failed.

Now, if you told me that you were having pain because a small lizard was chewing on the roof of your mouth, I might start to suspect a psychiatric problem.

I'd bet that BMS is caused by subtle damage of the main nerve that detects pain in the mouth, the trigeminal nerve. Indeed, one study provides support for that theory.

Low doses of tricyclic drugs or certain medicines often used for seizures may help reduce the symptoms. So may certain pain-killing medicines and creams applied directly to the parts of the mouth that hurt.

There are steps you can take to reduce your mouth discomfort. The National Institute of Dental and Craniofacial Research recommends the following to keep symptoms at bay:

-- Sip water frequently.

-- Suck on ice chips.

-- Avoid irritating substances. These include hot, spicy foods; mouthwashes that contain alcohol; and high-acid foods such as citrus fruits and juices.

-- Chew sugarless gum.

-- Avoid alcohol and tobacco.

(Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.)

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