Burning Mouth Syndrome Burning tongue is a syndrome in which an individual has a burning sensation in their mouth. The pain increase to the tongue, lips, and the internal part of the cheeks and to approximately all areas of the mouth. This may be caused due to different types of nutritional deficiencies, but most often, the cause of this Burning Mouth Syndrome is unknown. The symptoms are a burning sensation all over the mouth, dryness and sourness in the mouth, loss of taste, enhance in thirst and other eating or oral related conditions.