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Adult Skin Problems

Photo of herpes simplex lesion on the lower lip

Cold Sores (Fever Blisters)

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Courtesy of the Centers for Disease Control and Prevention (CDC)

Cold sores, sometimes called fever blisters, are groups of small blisters on the lip and around the mouth. The skin around the blisters is often red, swollen, and sore. The blisters may break open, leak a clear fluid, and then scab over after a few days. They usually heal after several days to 2 weeks.

Cold sores are caused by the herpes simplex virus (HSV). There are two types of herpes simplex virus: HSV-1 and HSV-2. Both virus types can cause lip and mouth sores and genital herpes.

The herpes simplex virus usually enters the body through a break in the skin around or inside the mouth. It is usually spread when a person touches a cold sore or touches infected fluid-such as from sharing eating utensils or razors, kissing an infected person, or touching that person's saliva. A parent who has a cold sore often spreads the infection to his or her child in this way. Cold sores can also be spread to other areas of the body. Read more about symptoms and treatments for cold sores.

Reviewed on September 15, 2009

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