An acute, recurrent, painful, noninfectious, ulcerative condition of the mouth. While the cause is unknown, it is likely that a variety of events are responsible for triggering localized immune-mediated mucosal damage. Aphthous ulcers occur in 15%-20% of the population. The most common form is recurrent aphthous stomatitis of the minor type. There are usually 1-5 ulcers at each episode, with each ulcer being less than 1 cm in diameter and healing in 7-14 days without scarring.