What are cold sores?
Cold sores, sometimes called fever blisters, are groups of small blisters on the lip and around the mouth. Often the first sign of a cold sore is a spot that tingles, burns, or itches. A blister usually forms within 24 hours. 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 in several days to 2 weeks.
What causes cold sores?
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 sores around the mouth (herpes labialis) and on the genitals (genital herpes).
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. A person can spread the virus to someone else a few days before the sore appears until the sore is completely healed. Cold sores can also be spread to other areas of the body.
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. You may also have 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 and disappear after several days to 2 weeks. For some people, cold sores can be very painful.
Some people have the virus but don't get cold sores. They have no symptoms.
How are cold sores diagnosed?
Your doctor can tell if you have cold sores by asking you questions to find out whether you have come into contact with the virus and by examining you. You probably won't need any tests.
How are cold sores treated?
Cold sores will usually start to heal on their own within a few days. But if they cause pain or make you feel embarrassed, they can be treated. Treatment may include skin creams, ointments, or sometimes pills. Starting treatment right away 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.
The herpes simplex virus that causes cold sores can't be cured. After you get infected, the virus stays in your body for the rest of your life. If you get cold sores often, treatment can reduce the number of cold sores you get and how severe they are.
How can you prevent cold sores?
There are some things you can do to keep from getting the herpes simplex virus.
- 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.
After you have been infected with the virus, there is no sure way to prevent more cold sores. But there are some things you can do to reduce your number of outbreaks and prevent spreading the virus.
- Avoid the things that trigger your cold sores, such as stress and colds or the flu.
- Always use lip balm and sunscreen on your face. Too much sunlight can cause cold sores to flare.
- 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. This can help keep you from spreading the virus to your eyes or genital area or to other people.
- Talk to your doctor if you get cold sores often. You may be able to take prescription pills to prevent cold sore outbreaks.
Cold sores are blisters on the lips and the edge of the mouth that are caused by an infection with the herpes simplex virus (HSV). Often the first sign of a cold sore is a spot that tingles, burns, or itches. A blister usually forms within 24 hours.
Cold sore blisters usually break open, weep clear fluid, and then crust over and disappear after a few days.
Other symptoms may include:
- A sore mouth that makes eating, drinking, and sleeping uncomfortable. Cold sores can be painful.
- A fever.
- A sore throat.
- Swollen lymph nodes in the neck.
- Drooling, in small children.
You may not develop cold sores when you are first infected with HSV. If cold sores do develop when you are first infected, they may be more severe than in later outbreaks. During the first outbreak of cold sores, the blisters may spread to any part of the mouth.
After you become infected, HSV remains in your body and may cause cold sores to return throughout your lifetime (recurrent cold sores).
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. This is called the prodromal stage.
Some common triggers that cause cold sores to return include:
- Sunlight exposure, especially on the lips.
- Stress or fatigue.
- Other infections, such as a cold or the flu.
- Food allergies.
- Dental treatment or injury to the lips or gums.
- An impaired (weak) immune system.
- Cosmetic surgery, such as dermabrasion or laser skin resurfacing.
- Pregnancy and hormonal changes in women caused by the menstrual cycle.
People who have weakened immune systems are more likely than those with strong immune systems to have longer or more severe outbreaks of cold sores. HSV infection may be life-threatening in certain people who have weak immune systems.
Who is at greatest risk for developing cold sores?
Anyone who is exposed to the herpes simplex virus (HSV) is at risk for developing cold sores. But many people have the virus and may never develop cold sores.
People who have weakened immune systems are at an increased risk for having more severe and longer-lasting outbreaks of cold sores.
One form of HSV infection, called primary herpes stomatitis, is seen most often in children 1 to 3 years old. It can cause a high fever and blisters throughout the mouth, which can interfere with the ability to eat. It can be serious in children—they can get quite sick from this illness, although they usually recover without any long-term problems.
Exams and Tests
Your doctor can diagnose cold sores by asking questions to find out whether you've been exposed to the herpes simplex virus (HSV) and by examining you. No further testing is usually needed.
There are two types of herpes simplex virus: HSV-1 and HSV-2. Both virus types can cause lip and mouth sores (herpes labialis) and genital herpes if your skin comes into contact with either type.
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, nor is there a cure for the herpes simplex virus (HSV) that causes them. Most cold sores will go away on their own. But medicines may slightly reduce the duration of cold sores and sometimes prevent a future outbreak.
Treatment with medicines depends on whether you are having a first outbreak or a recurrent outbreak or are trying to prevent future outbreaks.
When treating a first outbreak of cold sores, oral antiviral medicines may reduce pain and slightly improve healing time.
For treatment of recurrent cold sores, the following medicines may reduce the severity and duration of the outbreak:footnote 1
- Topical creams or ointments, which are available with or without a prescription, can reduce pain, itching, and healing time.
- Oral antiviral medicines, which are available by prescription only, may be used when the first symptoms (such as burning or itching) begin. Starting treatment right away 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.
Oral antivirals may also be taken daily to prevent recurring cold sores, especially in people who have frequent and painful outbreaks.
If you have a weakened immune system and develop cold sores, you may need medicines to control your symptoms or daily doses to prevent outbreaks.
The first episode of cold sores can be so painful that you may have trouble eating, drinking, and sleeping. A child who has a fever and many mouth sores may need to be encouraged to drink water and other fluids to prevent dehydration.
Adults and older children who have a painful first episode of cold sores may sometimes need a prescription-strength medicated mouth rinse to reduce pain.
Several complementary medicine treatments are available if you wish to try an alternative way to ease your symptoms.
Vitamin C, lysine supplements, and lemon balm are examples of complementary treatments that may provide some relief during a cold sore outbreak. Vitamin C may be taken as an oral tablet, in a cream that can be put on the cold sore (topical cream), or as liquid vitamin C applied to the cold sore. Lysine supplements are taken as pills, and lemon balm is available in a topical cream.
Zinc oxide topical cream may reduce the duration of an outbreak.footnote 1
Most cold sores heal on their own. But you can manage your symptoms at home by:
- Placing a cool, wet towel on the sores 3 times a day for 20 minutes each time to help reduce redness and swelling.
- Using a mouth rinse that has baking soda to soothe a sore mouth.
- Avoiding foods that contain acid (such as citrus fruits and tomatoes).
- Using nonprescription ointments that can relieve pain or help heal the cold sore.
- Some products such as Abreva and Zilactin can speed the healing of cold sores or prevent them if applied early enough.
- Other products such as Orajel and Anbesol can numb sore areas in the mouth or on the lips.
- Children age 2 and older can be treated with Zilactin-L Liquid, Orajel Baby, and Anbesol. Abreva is for people age 12 and older, so talk to your doctor before using it for a younger child. And if your child is younger than 2, talk to your doctor before using any of these medicines.
Ask your doctor if you can take ibuprofen (such as Advil or Motrin) or acetaminophen (such as Tylenol) to reduce pain. Do not give aspirin to anyone younger than 20 because of its link to Reye syndrome, a serious but rare problem. Be safe with medicines. Read and follow all instructions on the label
You can reduce the frequency of cold sore outbreaks by taking the following steps:
- Avoid prolonged exposure of your lips to sunlight. Protect your face from the sun. Using lip balm that contains sunscreen may help reduce outbreaks of cold sores.
- Avoid intimate contact (such as kissing) with people who have cold sores or genital herpes.
- Avoid sharing towels, razors, silverware, toothbrushes, or other objects that a person with a cold sore may have used.
These measures may help prevent the spread of cold sores in children:
- Encourage frequent hand-washing.
- Do not let children share toys that other children put in their mouths.
- Clean toys occasionally with a disinfectant.
- Do not let children kiss each other while they have cold sores or uncontrollable drooling.
- Use disposable gloves or a cotton swab to apply medicated ointment to a child's cold sores.
- Worrall G (2009). Herpes labialis, search date February 2009. Online version of BMJ Clinical Evidence: http://www.clinicalevidence.com.
Other Works Consulted
- Habif TP, et al. (2011). Herpes simplex section of Viral infections. In Skin Disease: Diagnosis and Treatment, 3rd ed., pp. 224–229. Edinburgh: Saunders.
- Sterling JC (2010). Herpes labialis. In MG Lebwohl et al., eds., Treatment of Skin Disease: Comprehensive Therapeutic Strategies, pp. 303–305. Edinburgh: Saunders Elsevier
- Wolff K, et al. (2013). Herpes simplex virus disease. In Fitzpatrick's Color Atlas and Synopsis of Clinical Dermatology, 7th ed., pp. 660–667. New York: McGraw-Hill.
Current as of: February 11, 2021