Picture of Cold Sore and Canker Sore
There are differences between cold sores and canker sores. Sores that break out on the lips are cold sores. Sores that break out inside the mouth are canker sores. Canker sores are not caused by the herpes virus and they are not contagious. The cause of canker sores is unknown. The skin of the lips may appear red and irritated before a cold sore actually breaks out in the area. A cold sore starts as a blister and then ruptures. It then becomes crusty before entering the healing stage.
Text Reference: National Institute of Dental and Craniofacial Research: “Fever Blister and Canker Sores”