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. The blisters may break open, leak a clear fluid, and then scab over after a few days. They usually heal after a few days to 2 weeks.

The first symptoms of cold sores may include pain around your mouth and on your lips, a fever, a sore throat, or swollen glands in your neck or other parts of the body. 

After the blisters appear, the cold sores usually break open, leak a clear fluid, and then crust over and disappear after several days to 2 weeks. 

Recurrent cold sores usually develop where facial skin and the lip meet. About 6 to 48 hours before a cold sore is visible, you may feel tingling, burning, itching, numbness, tenderness, or pain in the affected area. 

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 and genital herpes.   HSV-1 is the most common cause of cold sores.

The herpes simplex virus usually enters the body through a break in the skin around or inside the mouth. It is usually spread when a person touches a cold sore or touches infected fluid—such as from sharing eating utensils or razors, kissing an infected person, or touching that person's saliva. A parent who has a cold sore often spreads the infection to his or her child in this way. Cold sores can also be spread to other areas of the body.  For example, oral sex can transmit cold sores to the genital area of a sexual partner.

Anyone who is exposed to the herpes simplex virus (HSV) is at risk for developing cold sores. But many people may have the virus and may never develop cold sores. 

Your doctor can diagnose cold sores by asking questions to determine whether you've been exposed to the herpes simplex virus (HSV) and by examining you. No further testing is usually needed.

If it is 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 is usually not uncomfortable even if the sore is tender or painful. 

There is no cure for cold sores or for the herpes simplex virus (HSV).   After you are infected, the virus stays in your body for the rest of your life. However, if you get cold sores often, treatment can reduce the number of cold sores you get and how severe they are.

Most cold sores will go away on their own. But if they cause pain or make you feel embarrassed, they can be treated with prescription oral antiviral medications and non-prescription topical creams or ointments. Treatment may get rid of the cold sores only 1 to 2 days faster, but it can also help ease painful blisters or other uncomfortable symptoms. 

• Avoid coming into contact with infected body fluids, such as kissing an infected person.
• Avoid sharing eating utensils, drinking cups, or other items that a person with a cold sore may have used.

• Avoid things that trigger cold sores, such as stress, fatigue and colds or the flu.
• Always use lip balm with sunscreen and sunscreen on your face. Too much sunlight can cause cold sores to flare-up.
• Avoid sharing towels, razors, silverware, toothbrushes, or other objects that a person with a cold sore may have used.
• When you have a cold sore, make sure to wash your hands often, and try not to touch your sore.
• Parents of newborn babies should not kiss or nuzzle their babies until after the cold sore has cleared up.
• Talk to your doctor if you get cold sores often. You may be able to take prescription pills to prevent cold sore outbreaks.