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Cold Sores
Cold sores are red, fluid-filled blisters that usually form near the mouth. Learn about cold sore causes, symptoms, treatment, and prevention.

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What Are Cold Sores?

Cold sores are red, fluid-filled blisters that form near the mouth or on other areas of the face. In rare cases, cold sores may appear on the fingers, nose, or inside the mouth. They are usually clumped together in patches. Cold sores may persist for two weeks or longer.

Cold sores are caused by a common virus called herpes simplex. They can spread from person to person through close contact, such as kissing. The sores are contagious even when they aren’t visible.

There’s no cure for cold sores, and they may return without warning. Certain medications can be used to treat cold sores and prevent them from coming back.

What Causes Cold Sores?

Cold sores are caused by the herpes simplex virus. There are two types of the herpes simplex virus. The herpes simplex type 1 virus (HSV-1) usually causes cold sores, and the herpes simplex type 2 virus (HSV-2) typically causes genital herpes. The actual sores are similar in appearance for both forms of the virus. It’s possible for HSV-1 to cause sores on the genitals and for HSV-2 to cause sores on the mouth. However, this is very rare.

Visible cold sores are contagious, but they may be spread even when they can’t be seen. You can get the herpes simplex virus by coming in contact with infected individuals. This may happen through kissing, sharing cosmetics, or sharing food. Oral sex may spread both cold sores and genital herpes.


Once you catch the herpes simplex virus, it can’t be cured. Even after the sores have healed, the virus remains dormant in your body. This means that new sores can appear at any time. Some people with the virus report more frequent outbreaks when their immune systems are weak, such as during illness or times of stress.

Recognizing a Cold Sore

You may notice a tingling or burning sensation on your lips or face several days before a cold sore develops. Once the sore forms, you’ll see a raised, red blister full of fluid. It will usually be painful and tender to the touch. There may be more than one sore present.

The cold sore will remain for at least two weeks and will be contagious until it crusts over. Your first cold sore may not appear for up to 20 days after you contract the herpes simplex virus.

You may also experience one or more of the following symptoms during an outbreak:

  • fever
  • muscle aches
  • swollen lymph nodes

Touching your cold sore before touching your eyes can cause eye infections. You should call your doctor immediately if you develop an eye infection during a cold sore outbreak. Infections caused by the herpes simplex virus can lead to permanent vision loss when they’re not treated promptly.

Complications Associated with Cold Sores

The initial infection of herpes simplex can cause more severe symptoms and complications, as your body hasn’t built up a defense to the virus yet. Complications are rare, but can occur, especially in young children. Call your doctor immediately if you’re experiencing any of the following symptoms:

  • high or persistent fever
  • difficulty breathing or swallowing
  • red, irritated eyes with or without discharge

Complications are more likely to occur in people who have eczema or a condition that weakens their immune system, such as cancer or AIDS. If you do have any of these conditions, contact your doctor if you think you’ve contracted the herpes simplex virus.

Treating Cold Sores

There’s no cure for cold sores, but some people with the herpes simplex virus rarely have outbreaks. When cold sores do develop, there are several ways to treat them.

Ointments and Creams

When cold sores become bothersome, you may be able to control pain and promote healing with antiviral ointments, such as penciclovir (Denavir). Ointments tend to be most effective if they’re applied when a sore first appears. They will need to be applied four to five times per day for four to five days.

Docosanol (Abreva) is another treatment option. It’s an over-the-counter cream that can shorten an outbreak by anywhere from a few hours to a day. The cream must be applied several times per day.


Cold sores can also be treated with oral antiviral medications, such as acyclovir (Zovirax), valacyclovir (Valtrex), and famciclovir (Famvir). These drugs are available by prescription only. Your doctor may instruct you to take antiviral medications regularly if you’re experiencing complications with cold sores or if your outbreaks are frequent.

Home Remedies

Symptoms may be eased by applying ice or washcloths soaked in cold water over the sores. Alternative treatments for cold sores include taking lysine supplements or using lip balm containing lemon extract.

Preventing Cold Sores from Spreading

To prevent spreading cold sores to other people, you should wash your hands often and avoid skin contact with others. Make sure you don’t share items that touch your mouth, such as lip balm and food utensils, with other people during an outbreak. It’s also important to avoid touching your eyes and genitals while cold sores are present. The herpes simplex virus can cause eye infections and genital herpes.

Written by: Marissa Selner
Edited by:
Medically Reviewed by: [Ljava.lang.Object;@35e47c2a
Published: Jul 18, 2012
Published By: Healthline Networks, Inc.
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