Cold Sores

Topic Overview

What are cold sores?

Cold sores, sometimes called fever blisters, are clusters of small blisters on the lip and outer edge of the mouth. The skin around the blisters is often red and inflamed. The blisters can break open, weep a clear fluid, and then scab over after a few days. Complete healing may take 7 to 10 days.

See an illustration of cold sores .

What causes cold sores?

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 (herpes labialis) and genital herpes if your skin comes into contact with either type.

What are the symptoms?

You can be infected with HSV and have no symptoms. For some people, however, cold sores can be painful. Initial symptoms can include mouth soreness, fever, sore throat, or swollen lymph glands. Small children sometimes drool before a cold sore appears. After the blisters develop, cold sores usually break open, weep clear fluid, and then crust over and disappear after several days to a week.

How are cold sores diagnosed?

Your health professional can diagnose cold sores by asking you questions to determine whether you have been exposed to HSV and by examining you. No further testing is usually needed.

How are cold sores treated?

Cold sores will usually go away on their own within a few days. But if they are severe or cause you embarrassment or discomfort, cold sores can be treated. Treatment may include topical creams or ointments or sometimes antiviral medicines (such as acyclovir or famciclovir). Treatment may reduce the duration of the cold sores by only 1 to 2 days, but it can help soothe painful blisters or other uncomfortable symptoms.

The herpes simplex virus that causes cold sores cannot be cured. If sores develop regularly, treatment can reduce the number and severity of outbreaks.

How are cold sores spread?

The herpes simplex virus usually enters your body through a break in the skin around or inside your mouth. It is spread through coughing, sneezing, direct contact with a cold sore, or touching contaminated fluid—such as from kissing an infected person and touching the person's saliva.

The virus can also be spread from one person to an area of someone else's body by touching an active cold sore or sharing things that a person who has a cold sore has used. A parent who has a cold sore often spreads the infection to his or her child.

Frequently Asked Questions

Learning about cold sores:	What are cold sores? What causes cold sores? How can I prevent cold sores? What are the symptoms of cold sores? Who is affected by cold sores? How are cold sores spread?
Being diagnosed:	How are cold sores diagnosed? What is a herpes test?
Getting treatment:	How are cold sores treated?
Living with cold sores:	What can I do at home to relieve symptoms of cold sores?

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Author:	Ralph Poore	Last Updated April 7, 2006
Medical Review:	Kathleen Romito, MD - Family Medicine Alexander H. Murray, MD, FRCPC - Dermatology
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