The initial symptom is a tingling or mildly painful itching sensation in the area where the sore will appear. After one to several days, a small red swelling appears. The sore is round, it is a whitish color with a grayish colored center. Usually, there is a red ring of inflammation surrounding the sore. The main symptom is pain.
Canker sores can be very painful, especially if they are touched repeatedly, e.g., by the tongue.
They last for one to two weeks. Diagnosis Canker sores are diagnosed by observation of the blister. A distinction between canker sores and cold sores must be made because cold sores are infectious and the herpes infection can be transmitted to other people. The two sores can usually be distinguished visually and there are specific diagnostic tests for herpes infection. Since canker sores heal by themselves, treatment is not usually necessary.