what are fever blisters in the mouth
Cold sores and fever blisters are caused by herpes simplex virus type 1 (HSV-1). This virus is passed from person to person by saliva (either directly, or by drinking from the same glass or cup) or by skin contact. Cold sores usually appear as clusters of tiny blisters on the lip. About 8 out of 10 people have the virus that causes cold sores.