Canker sores, also known as aphthous ulcers, are small, painful sores that develop inside the mouth. The exact cause of canker sores is not fully understood, but several factors can trigger them. Common causes include minor mouth injuries (such as from dental appliances, rough teeth cleaning, or accidentally biting the cheek or tongue), emotional stress, hormonal changes (like variations in the menstrual cycle), food allergies, and certain nutritional deficiencies (such as iron, vitamin B-12, and folic acid). They may also be linked to weak immune systems, viral infections, and some medical conditions like Behçet's disease and inflammatory bowel diseases. Acidic or citrus foods can sometimes trigger canker sores as well.
In summary, canker sores result from a combination of immune system factors, minor trauma inside the mouth, nutritional deficiencies, hormonal changes, stress, and possibly genetic predisposition.
