Canker sores — also known as aphthous ulcers — are small, painful lesions that form inside the mouth. They often appear suddenly, but what most people don’t realize is that canker sores form not just from one cause, but from a complex mix of biological, nutritional, emotional, and even environmental triggers. This post explores how do canker sores form by delving into what your body might be silently trying to tell you. 🔬 The Science Beneath the Surface: What Is a Canker Sore? A canker sore is not contagious, unlike cold sores caused by the herpes virus. It usually appears as a round or oval ulcer with a white or yellow center and a red border, typically developing on the soft tissues inside the cheeks, lips, tongue, or even the base of the gums. These sores are a type of ulcerative lesion , and while they are mostly harmless, they can be intensely painful. According to the American Academy of Oral Medicine , canker sores affect about 20% of the population at any given time — ...