Mouth ulcers may be caused by the following: Hot or spicy food Repeated rubbing from an ill-fitting denture Stress (canker sores or “aphthous ulcers”) A viral infection Erosive Lichen Planus (an autoimmune disorder) Cancer
Most mouth ulcers are caused by trauma (pizza burns) or stress (canker sores). People with weakened immune systems may be more susceptible to both canker sores and certain viral infections which show up as groups of small ulcers in the mouth. Trauma from an ill-fitting denture can also cause ulcers. More rarely, mouth ulcers may be caused by cancer.
Note the size, appearance, location and duration of the ulcer. Determine if it is painful, and recall if you may have traumatized the area. If an ulcer persists beyond one week, have the area examined by your dentist.
If the ulcer is the result of a disease process, it may worsen if left untreated. If it is caused by ongoing trauma, it may also worsen with time. In the rare event that it is cancer, it can lead to disfigurement or death if not diagnosed and treated in a timely manner.