The exact cause of canker sores is unknown, but doctors believe they are triggered by minor oral injuries, allergic reactions to bacteria, food sensitivities and emotional stress, Mayo Clinic states. Dietary deficiencies, such as low iron, and products containing sodium lauryl sulfate, such as toothpaste, are also suspected triggers.
Canker sores related to oral injuries are usually linked to minor tissue damage from dental work, brushing the teeth too roughly or biting the inside of the cheek, according to Mayo Clinic. Multiple factors may contribute to the formation of mouth ulcers. For example, individuals may irritate injured tissue by consuming sensitive foods, such as chocolate, nuts, coffee, eggs or acidic products. The presence of Helicobacter pylori bacteria in the mouth is linked to both canker sores and peptic ulcers.
People with dental devices installed, such as braces or dentures, are susceptible to canker sores, while existing medical conditions, including Crohn’s disease and celiac disease, are also known to increase their occurrence, WebMD notes. Canker sores are shallow lesions that commonly cause pain on the roof of the mouth, the lining of the cheeks or the tongue. These sores stop hurting within a few days and clear up completely within two weeks, but if they do persist, doctors can prescribe corticosteroid ointment for pain management or antimicrobial mouthwash to promote healing.