About This Condition
Canker sores are small ulcerations within the mouth.
Doctors call this common condition aphthous stomatitis.
Canker sores appear alone or in clusters as shallow, painful erosions in the mucous membrane inside the mouth. They typically have slightly raised, yellowish borders surrounded by a red zone, and are sometimes covered with a yellowish opaque material. Fatigue, fever, and swollen lymph nodes may be present in severe attacks.