Whether you call it a cold sore or a fever blister, oral herpes is a common infection of the mouth area caused by the herpes simplex virus type 1 (HSV-1). Estimates suggest that between 50 and 80 percent of Americans have been infected with this virus. Cold sores, also known as fever blisters, are small, fluid-filled blisters that appear on and around the lips. These blisters often form in patches and once they break, a crust forms and can last for several days.
Generally, cold sores heal without scarring in two to three weeks. The herpes simplex virus is responsible for cold sores. Once you have been infected with this virus, it may be triggered from time to time in the future. When the virus is activated or reactivated, it “wakes up” and travels through the nerves to the lips, where a cold sore develops. Most people become infected with oral herpes during childhood or when they were young adults through non-sexual contact with infected saliva. The herpes simplex virus can be difficult to diagnose because it can be confused with many other infections, such as allergic reactions.
Once you've had an episode of herpes infection, the virus remains latent in nerve cells in the skin and can appear as another cold sore in the same place as before. The virus is spread through physical contact, such as kissing, sharing a toothbrush, even sharing a drinking glass or through sexual contact. Sometimes, oral and genital herpes viruses can spread, even when there are no sores or blisters in the mouth.