Overview
Aphthous stomatitis (recurrent aphthous stomatitis, RAS; aphthous ulcers; 'canker sores') is characterized by recurrent, painful oral ulcers on non-keratinized mucosa, typically with a yellow-grey pseudomembranous base and an erythematous halo.
Despite extensive research, the etiology remains incompletely understood — it is not caused by the herpes simplex virus (a common misconception) and is not infectious.
RAS significantly impacts quality of life, with recurrent episodes of pain interfering with eating, speaking, and oral hygiene. Severe forms can be incapacitating.