Cold Sores (Fever Blisters)

What are cold sores?

Cold sores are annoying, small, painful blisters on the lips and nearby skin, including in the nose and mouth. They usually appear when you are sick or stressed. They are also called fever blisters.

How do they occur?

Cold sores are caused by the herpes simplex virus. This virus also causes genital herpes. The fluid in the blisters contains live virus. The virus in this fluid can easily be spread from one person to another. The infection can be spread, for example, by kissing, by sharing food or drink, or by not washing your hands after touching the sores.

Once you are infected, the virus continues to live in the body, even after the sores are gone. The virus may become active again and cause more cold sores during or after:

• injury, such as a scrape or too much exposure to the sun
• physical illness, such as a cold
• dental treatment
• emotional stress or fatigue
• hormonal changes caused by pregnancy or a woman's menstrual cycle.

It is not possible to predict how often you will have cold sores. Some people never have them again, but others have them regularly.

What are the symptoms?

About 24 hours before you can see blisters, you may have a sense of numbness, tingling, itching, or burning. Then a small cluster of tiny blisters appears on your lip or the skin around your lips. The blisters may be somewhat painful. Over the next few days, the blisters break and fluid drains out. This fluid is very contagious. As the blisters dry, they become sores that are covered with a yellowish dried crust and they become less painful.

How are they diagnosed?

Your healthcare provider can usually determine from your history and a physical exam whether the blisters are fever blisters. Fluid from the blisters may be tested in the lab (viral cultures).

How are they treated?

There are many nonprescription medications that provide some relief from the symptoms. A nonprescription antiviral medicine applied several times a day to the area as soon as the symptoms start may lessen symptoms. It may also help the sores heal more quickly.

Your healthcare provider may prescribe an oral antiviral medicine, such as acyclovir, valacyclovir, or famciclovir. This medicine stops the virus from reproducing itself. It must be taken when you first start having symptoms. The medicine does not eliminate the virus from the body, but it can decrease the number of days you have symptoms and help the blisters dry up more quickly. If you have cold sores often, your provider may recommend taking antiviral medicine daily to try to stop outbreaks from recurring.

How long will the effects last?

The blisters usually last 7 to 10 days. They should be considered contagious as long as you have any moist secretions from the blisters. They may return often (for example, several times a year) or rarely, such as once every few years.

How can I take care of myself?

• Taking a nonprescription painkiller such as aspirin, acetaminophen, or ibuprofen may help cold sores feel less painful.
• Putting ice on the blisters may also help lessen the pain.

What can I do to help prevent cold sores?

• Avoid touching any area of the body where there is tingling, itching, burning, or blisters. (This is very important when the blisters are draining.) Also avoid contact with items that touch the sores, such as eating utensils and facial tissues.
• Practice good hand washing.
• Take care to avoid spreading the virus to other susceptible areas of your body, such as the eyes and the genitals.
• Avoid kissing and any other contact of the sores with another person's skin.
• Avoid sharing soaps, washcloths, cosmetics (including lip balm), and utensils for eating or drinking.
• Just as genital herpes can be spread to the mouth by oral-genital sex, cold sores can be spread to the genitals by oral-genital sex. Be careful not to pass the oral cold sores to your sexual partner(s).
• Use a lip balm containing sunscreen whenever your lips are exposed to the sun.
• If you are caring for someone with the herpes virus, do not touch the sores directly. Use gloves or gauze to apply medicine.
• Your provider may prescribe an antiviral medicine for you to take when you know you are going to be exposed to something that causes you to have cold sores, such as a lot of sun or stress.