causes of fever blisters
Fever blisters are one of the most common conditions of the mouth. Also known as cold sores (and known medically as herpes labialis), fever blisters are caused by a contagious virus called the herpes simplex virus.There are two types of herpes simplex viruses: 1  Herpes simplex type 1 (HSV-1).n fact, more than 95 percent of recurrent fever blister outbreaks are caused by HSV-1. Most people infected with the HSV-1 virus usually become infected before they are 10 years old. On the other hand, HSV-2 most commonly causes genital herpes (see Genital Herpes Causes) .