REASONS OF BURNING SENSATION IN THE MOUTH: They include: Acid reflux (acid from your stomach comes back up into your mouth) Diabetes. Dry mouth (caused by such conditions as Sjogren's syndrome, certain medications, or radiation therapy) Lack of iron, vitamin B12, or folic acid. Thrush (a fungal infection in your mouth) Thyroid problems. What causes your mouth to feel like it's burning? Oral yeast infection (thrush) is a common cause of a burning mouth that may also occur with other causes, such as diabetes, denture use and certain medications. Geographic tongue, a condition that causes a dry mouth and a sore, patchy tongue, also may be associated with burning mouth syndrome.