Why do mouth ulcers form?

Canker sores appear most often when your immunity drops from fatigue, stress, or lack of sleep. Other causes include a shortage of vitamin B12, iron, or folate, wounds from biting your cheek or tongue, and irritation from orthodontic appliances or dentures. Most heal on their own within 1 to 2 weeks, but an ulcer that keeps returning in the same place or does not heal within 2 weeks needs to be distinguished from other conditions, so please come in to have it checked.