They are caused by the herpes simplex virus. This name tends to strike fear in the hearts of those who hear it because they recognize it as the virus associated with genital herpes, a sexually transmitted disease. However, these viruses, while similar in name, tend to be distinct types of infections.
Some children acquire the virus but have few, if any, symptoms.
Others get the infection and develop many sores in and around the mouth. These blisters can be quite painful and may be associated with low-grade fevers. Fortunately , the initial severe infection tends to be a one-time occurrence. Unfortunately , once infected, children become carriers of the virus, which may last a lifetime. Some children never have another cold sore after the initial infection, while others develop recurrent sores, usually after episodes of stress such as fever, sunburn or injury to the mouth.