Canker sores, technically known as aphthous ulcers, are small, shallow lesions that develop on the soft tissues in your mouth or at the base of your gums. They can be painful and can make eating and talking difficult. Unlike cold sores, canker sores don’t occur on the surface of your lips and aren’t contagious. In the vast majority of cases, canker sores are hereditary and occur after local trauma to the mouth. Most canker sores heal spontaneously within 1 or 2 weeks; however, topical and systemic therapy is available to expedite the healing process.