A cold sore is an annoying, small, painful blister on the lips or nearby skin, including in the nose and mouth. Cold sores usually appear when you are sick or stressed. They are also called fever blisters.
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:
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 at any time. It is especially likely to become active again during or after:
It is not possible to predict how often you will have cold sores. Some people never have them again after the first time, but others have them regularly.
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.
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 to confirm the diagnosis of herpes simplex virus. The test is called a viral culture.
A nonprescription antiviral medicine called docosanol (Abreva) may lessen symptoms. It may also help the sores heal more quickly. It needs to be put on the area with blisters several times a day as soon as the symptoms start. There are many other nonprescription medicines that can give some relief from the symptoms.
Your healthcare provider may prescribe an oral antiviral medicine, such as acyclovir, valacyclovir, or famciclovir. This medicine stops the virus from making more viruses. To prevent the blisters, the medicine must be taken when you first start having symptoms. The medicine does not get rid of the virus, 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. Or 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
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.
Use a lip balm containing sunscreen whenever your lips are exposed to the sun. Avoid being out in the sun too much. This often causes outbreaks of blisters.
To prevent spreading the virus to other parts of your body:
To prevent spreading the virus to others:
To keep from getting the cold sore virus from someone else: