What do Fever Blisters Look Like?

Fever blisters--also commonly called cold sores--are caused by herpes simplex virus type 1 (HSV-1). Fever blisters are common, and you can't cure or prevent cold sores once you have been infected with the virus. You can reduce the time they take to heal, however, and possibly cut down on the number of recurrent infections you get as well.

Fever blisters are small, painful blisters filled with fluid. They appear on a raised, reddened area of your skin--most commonly on the mouth and lips, although they occasionally break out on nostrils, chins or fingers. The blisters cause pain or a tingling sensation that is usually noticed a day or two before the blister forms.

Fever blisters last from 7 to 10 days, although symptoms may not start for as long as 20 days after exposure to the herpes simplex virus. Over that period of time, the blisters will develop, break and then ooze. After the blister breaks and oozes, a yellow crust will form that will eventually come off, leaving new unscarred skin.

Fever blisters are often associated with canker sores--sores on the inside of the mouth and tongue--but actually they are not related at all. Fever blisters are almost never inside the mouth; if they are, they are usually found on the gums or the hard palette (roof) of the mouth. Because cold sores are caused by a herpes virus, people often link them to the sexually transmitted disease herpes.

Herpes as a sexually transmitted disease is typically an infection of herpes simplex virus type 2 (HSV-2) not HSV-1--although both viruses can cause sores on the mouth and genitals. Fever blisters generally clear up on their own with or without treatment over 7 to 10 days. There are antiviral medications that may shorten the duration of the infection by a small amount.

There are also medications that will reduce your pain. It may be possible to prevent fever blisters by following a few simple steps. Avoid skin-to-skin contact--including kissing--with people who have active blisters.

Don't share utensils, towels, chap sticks or other personal hygiene items associated with the infected area. Wash your hands regularly--if you're infected, be sure to wash your hands thoroughly before touching anyone else. Some individuals with recurrent infections may find that they are more prone to fever blisters when they are overly tired, have the cold or the flu, or are exposed to the sun for long periods of time.

The herpes virus that causes fever blisters is contagious. It can be spread from person to person through skin-to-skin contact. The risk of infection is at its peak during the time when blisters are erupting and until they've dried and crusted over.

Be aware that the virus can spread even after the skin has healed. Persons with diseases or conditions that compromise their immune system should avoid contact with individuals who are infected with the herpes virus, as their weakened immune systems are likely to make a herpes infection much more serious.