Are fever blisters and canker sores the same thing?
No. Canker sores occur only inside the mouth and are not contagious. They sometimes occur as a result of trauma (biting the inside of the lip, burning the mouth with hot food), but may also occur without any known reason.
Fever blisters or cold sores are caused by herpes simplex virus type 1 and are very contagious. Fever blisters often come back in the same location.
Canker sores and fever blisters