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Cold Sores

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Cold Sores

Condition Basics

What are cold sores?

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. They usually heal in 7 to 10 days. Cold sores are most contagious until the blisters are completely healed.

What causes them?

Cold sores are caused by the herpes simplex virus (HSV). HSV usually enters the body through a break in the skin around or inside the mouth. Cold sores can easily spread to others until the blisters are completely healed.

What are the symptoms?

The first symptoms of cold sores may include a spot that tingles, burns, or itches around your mouth and on your lips. A blister usually forms within 24 hours.

You may also have a sore mouth, a fever, a sore throat, or swollen glands in your neck or other parts of the body. Small children sometimes drool before cold sores appear.

After the blisters appear, the cold sores usually break open, leak a clear fluid, and then crust over. They usually heal in 7 to 10 days. For some people, cold sores can be very painful.

Some people have the virus but don't get cold sores. They have no symptoms.

You may not get cold sores when you are first infected with the herpes simplex virus (HSV). If cold sores do form when you are first infected, they may be more severe than in later outbreaks.

How are they diagnosed?

Your doctor can tell if you have cold sores by looking at the sore and asking you questions to find out if you have come into contact with the herpes simplex virus. You probably won't need any tests.

If it's not clear that you have cold sores, herpes tests may be done. The doctor takes a sample of fluid from a sore and has it tested. Having the sample taken usually isn't uncomfortable even if the sore is tender or painful.

How are cold sores treated?

Cold sores usually start to heal on their own in 7 to 10 days. Treatment can get rid of cold sores faster, and it can also help ease painful blisters or other symptoms.

Treatment may include:

  • Oral antiviral medicines. These can reduce pain and slightly improve healing time.
  • Topical creams or ointments. They may reduce pain, itching, and healing time.

To prevent recurring cold sores, oral antivirals may also be taken daily. This can be especially helpful for people who have frequent and painful outbreaks.

There is no cure for cold sores or the virus that causes them.

How can you prevent them?

There are some things you can do to keep from getting the virus that causes cold sores.

  • Avoid kissing a person who has cold sores.
  • Avoid sharing utensils, cups, or other items that a person with cold sores may have used.

If you've already been infected, reduce your number of outbreaks and prevent spreading the virus.

  • Avoid things that trigger your cold sores, such as stress and colds or the flu.
  • Always use lip balm and sunscreen on your face.
  • When you have a cold sore, wash your hands often. Try not to touch your sore.
  • Talk to your doctor if you get cold sores often.

Help prevent the spread of cold sores in children.

  • Encourage frequent hand-washing.
  • Don't let children share toys that other children put in their mouths.
  • Clean toys occasionally with a disinfectant.
  • If children have oozing cold sore blisters, keep them home until the blisters scab over.

Related Information


Current as of: August 6, 2023

Author: Healthwise Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

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