canker sore, an ulcerous lesion of the mouth, characteristic of aphthous stomatitis. It is hereditary and not contagious. Most often, the sores heal without treatment. Sodium lauryl sulfate, which is present in most toothpastes, may worsen the symptoms. Antimicrobial mouthwashes or corticosteroid topical treatment are sometimes prescribed. See also aphthous stomatitis.
