What is burning mouth syndrome?

Many causes. Burning mouth can be caused by a number of things. I usually evaluate for vitamin deficiencies like B12 and folate (folic acid). I have seen it with patients who are hypothyroid as well. Sjogren's disease can cause it as well as acid reflux.
Nerve malfunction. Bms is a complex interaction of disrupted nerve signals. Ranial nerves 5, 7, and 9 travel through 'holes' in the base of the skull on their path from the spinal column to the tongue. Swollen muscles, ruptured blood vessels, cysts, tumors, pinched nerves, broken bones, hormones, vitamin deficiencies can all alter the sensation interpreted as 'burning' or painful. See a doc for a neuro consult.
Cause ? Burning mouth syndrome is given to pain of the tongue, and other areas of the mouth when the cause is not readily apparent. See your physician for a medical evaluation to try to determine the cause. Even if the cause cannot be determined, there are methods and medications to relieve the discomfort.
Difficult to diagnos. It is sometimes difficult to diagnose as several things can cause it. A multidisciplinary approach is best to determine the cause.