Cold sore


Cold sores are small red blisters, filled with clear fluid, that form on the lip and around the mouth. Rarely, they form on the roof of the mouth. Cold sores are caused by the herpes simplex virus type 1 (HSV-1), which lives inside nerve tissue. Despite their name, cold sores have nothing to do with colds. The herpes simplex virus type 1 should not be confused with the herpes simplex virus type 2 (HSV-2), which most often causes genital herpes.


There are eight different kinds of human herpes viruses. Only two of these, herpes simplex types 1 and 2, can cause cold sores. It is commonly believed that herpes simplex virus type 1 infects above the waist and herpes simplex virus type 2 infects below the waist. This is not true. Both herpes virus type 1 and type 2 can cause herpes lesions on the lips or genitals, but recurrent cold sores are almost always type 1.

The sores can appear within days or weeks or even years following the first exposure to the virus. The first time symptoms appear they are usually more intense than later outbreaks. For example, some children experience more pain at the blister site or even flu-like symptoms, including swollen glands, fever , or sore throat . Medical names for cold sores include oral herpes, labial herpes, herpes labialis, and herpes febrilis.


Herpes simplex virus is transmitted by infected body fluids (such as saliva) when they contact breaks in another person's skin or mucous membranes. Newborns may become infected during delivery through an infected birth canal. HSV-1 can be passed to children by parents, nurses, and caregivers who fail to practice careful hand washing. Children with burns , eczema, or diaper rash or those who are immunosuppressed are highly susceptible to the herpes virus.

VIRUS VERSUS BACTERIA Viruses behave differently than bacteria. While bacteria are independent and can reproduce on their own, viruses enter human cells and force them to make more viruses. The infected human cell dies and releases thousands of new viruses. The cell death and resulting tissue damage causes the cold sores. In addition, the herpes virus can infect a cell, and instead of making the cell produce new viruses, it hides inside the cell and waits. The herpes virus hides in the nervous system. This action is called latency. A latent virus can wait inside the nervous system for days, months, or even years. At some future time, the virus "awakens" and causes the cell to produce thousands of new viruses that cause an active infection.

Latent and active infection is understood by considering the cold sore cycle. The first infection is the primary infection. The primary infection is controlled by the body's immune system and the sores heal. Between active infections, the virus is latent. At some point in the future, latent viruses become activated and once again cause sores or recurrent infections. Although it is unknown what triggers latent virus to activate, several conditions bring on infections. These include stress, illness, fever, fatigue, exposure to sunlight, menstruation , and diet.


The herpes simplex virus is widespread in children. Thirty-five percent of five-year olds carry HSV-1 antibodies. A primary infection commonly occurs by the time a child reaches age five. These viral infections are more common in lower socioeconomic groups.

Nearly 80 percent of the general population carry the herpes simplex virus that causes cold sores, and 60 million have outbreaks once or more in a year. Most infants and children harbor the herpes virus before age ten. Interestingly enough, only 20 percent to 25 percent of those carrying the virus ever gets symptoms (break out in cold sores).

Causes and symptoms

While anyone can have the herpes virus infection, not everyone will show symptoms. The first symptoms of herpes occur within two to 20 days after contact with an infected person. Symptoms of the primary infection are usually more severe than those of recurrent infections. The primary infection can cause symptoms like other viral infections, including fatigue, headache , fever, and swollen lymph nodes in the neck.

Typically, 50 to 80 percent of children with oral herpes experience a prodrome (symptoms of oncoming disease) of pain, burning, itching , or tingling at the site where blisters will form. This prodrome stage may last a few hours or one to two days. The herpes infection prodrome occurs in both the primary infection and recurrent infections.

In 95 percent of the patients with cold sores, the blisters occur at the outer edge of the lips, which is called the vermillion border. Less often, blisters form on the nose, chin, or cheek. Following the prodrome, the disease process is rapid. First, small red bumps appear. These quickly form fluid-filled blisters.

Causes of cold sores in children

Infants are most likely to get a cold sore because someone with an active virus kisses them. The cause can even be a kiss from someone who did not have a visible sore but had the virus in his or her saliva. A baby may also get the herpes virus passing through the birth canal if the mother has genital herpes.

Once a child gets the virus, it stays in his body permanently, hiding in nerve cells near the ear. In some children, the virus lies dormant and never causes harm. In others, it periodically wakes up and triggers cold sores. Nobody knows what stirs the virus into action, but stress, fever, colds, and sunburn encourage outbreaks. Rich foods such as chocolate, food allergies , or hormonal changes may also cause outbreaks in children and adolescents.

Symptoms of cold sores in infants

The first symptoms of cold sores in infants are swollen gums and sore mouth. A few days later, there is a cluster of small blisters on or near the lips that turn into a shallow, painful sore. The breakout is often accompanied with fever and swollen lymph glands in the neck. In a few days the sore will crust and slowly disappear. The whole flare-up lasts about seven to ten days. The next time the infant has an outbreak the blister is the first symptom, not the swollen gums and painful mouth. If not treated, recurring outbreaks may last longer.

Stages of cold sores in children and adolescents

Cold sores, untreated, can last up to 14 days. Children often feel the tingling at the site before the sore appears. Parents should begin the treatment at the first sign of tingling or redness, which can reduce the time to two to four days. Beginning treatment after the blister appears can also significantly reduce the time and degree of pain. The following describes the stages of a cold sore:

  • Day 1: Prodrome (tingle) stage: Before a blister appears, the child usually feels a tingling, itching, or burning sensation beneath the skin, usually around the mouth or the base of the nose. This is the best time to start treatment.
  • Days 2 to 3: The blister or blisters appear. Children usually have one or several blisters on or around the moth, most often at the border of the lip and the skin on the face. Cold sores occasionally occur on the roof of the mouth.
  • Day 4: Ulcer or weeping stage: The blister opens, revealing a reddish area. The child is most contagious and in the most pain at this point.
  • Days 5 to 8: Crusting stage: The blisters dry up, and a crust forms which is yellow or brown in color. Children should be told not to pick at this crust.
  • Days 9 to 14: Healing stage: A series of scabs form over the sore, each smaller than the previous one until the cold sore is healed.

When to call the doctor

The HSV-1 virus can cause ocular herpes, a serious eye infection affecting the cornea (the clear window) of the eye, which can threaten vision and needs immediate medical attention and treatment. When a baby or child has a cold sore, parents should do all they can to keep them from touching their eyes. If a painful sore appears on the child's eyelid, eye surface, or on the end of his nose, call the pediatrician right away. The child may need antiviral drugs to keep the infection from scarring the cornea. Ocular herpes can weaken vision and even cause blindness.

Some children have a serious primary (first episode) herpes infection called gingivostomatitis, which causes fever, swollen lymph glands, and several blisters inside the mouth and on the lips and tongue that may form large, open sores. These painful sores may last up to three weeks and can make eating and drinking difficult. Because of this problem, young children with gingivostomatitis are at risk for dehydration . Children with this condition should be seen by a doctor.

Most infants have protection for at least six months from HSV-1 by antibodies they received from their mothers. But if a newborn gets a cold sore, the pediatrician should be called right away.

If the immune system of children is compromised because of cancer treatment or AIDS , they could have more serious problems with the herpes virus. Parents should let the doctor know if these health conditions exist.

Children with a history of frequent herpes flare-ups who spend time skiing or on the beach should call a doctor for a prescription for starting oral anti-herpes medication (pills) before such outings and then using sunscreen while they are outside. These precautions can prevent most outbreaks.


Cold sores are diagnosed by review of symptoms, physical examination, and history. The diagnosis is confirmed by various viral tests. A Tzanck or Papanicolau smear may be done. A positive smear cannot distinguish between varicella zoster virus and HSV-1, and a negative smear does not rule out HSV infection. Tissue culture provides a more reliable method of diagnosis. Cells killed by the herpes virus have a certain appearance under the microscope. Laboratory blood test looks for the virus or to confirm the presence of antibodies that fight the virus.

Approximately 85 percent of active herpes infections are without symptoms. When the symptoms do appear, they have the following sequence:

  • burning, itching, or tingling at the site before the sore appears
  • clusters of fluid-filled vesicles ulcerate, dry, and crust
  • lesions dry and crust within seven to ten days
  • usually one or two lesions present on the lips, tongue, gingival, or buccal mucosa
  • puritis (itching) and pain


There is no cure for herpes virus infections. Antiviral drugs are available that have some effect on lessening the symptoms and decreasing the length of herpes outbreaks. There is evidence that some may also prevent future outbreaks. These antiviral drugs work by interfering with the reproduction of the viruses and are most effective when taken as early in the infection as possible. For the best results, drug treatment should begin during the prodrome stage before blisters are visible. Depending on the length of the outbreak, drug treatment could continue for up to ten days.

Antiviral pills such as acyclovir (Zovirax), famciclovir, (Famvir), and valacyclovir (Valtrex) can cancel an outbreak and help prevent recurrent outbreaks. Acyclovir (Zovirax) is the drug of choice for herpes infection and can be given intravenously or taken by mouth. A liquid form for children is also available. Acyclovir is effective in treating both the primary infection and recurrent outbreaks. When taken by mouth, acyclovir reduces the frequency of herpes outbreaks.

Antiviral creams Zovirax and Denavir should be applied within the first 24 hours of feeling the tingling or discomfort, before the plaster erupts. The duration of the outbreak can be shortened by a day or two. Antiviral creams are not as effective as the pills.

During an outbreak, sores should be washed once or twice a day with warm, soapy water, and gently patted dry. Over-the-counter lip products that contain the chemical phenol (such as Blistex Medicated Lip Ointment) and numbing ointments (Anbesol) help to relieve cold sores. A bandage over the sores protects them and prevents spreading the virus to other sites on the lips or face.

Close-up view of a cold sore, caused by herpes simplex virus, on a patients mouth. ( Kenneth Greer/Visuals Unlimited.)
Close-up view of a cold sore, caused by herpes simplex virus, on a patient's mouth.
(© Kenneth Greer/Visuals Unlimited.)

Acetaminophen (Tylenol) or ibuprofen (Motrin, Advil) may be necessary to reduce pain and fever.

Alternative treatment

Cold sores in infants and children will go away on their own, but there are measures that will help the child feel better:

  • To ease the pain, apply ice to the sore, or if the doctor approves, give the baby a mild pain reliever, such as ibuprofen or acetaminophen. (Do not give aspirin to a baby; it could trigger Reye's syndrome. This is a rare but potentially life-threatening illness.) Choices for pain relief include medication, ointments, or mouth rinses recommended by the pediatrician. Parents may also use Oragel, an ointment often used for canker sores or teething.
  • Avoid giving the child spicy, salty, or sour foods, and foods with acid (oranges and grapefruits), which can irritate the open sore.
  • Apply a water-based zinc ointment such as Desitin. It helps dry out the sore so it can heal faster.
  • Extra sleep and plenty of liquids to drink can help.

Adolescents can learn to manage their own outbreaks. They can take the following steps:

  • Use over-the-counter pain relievers, such as acetaminophen (Tylenol) or ibuprofen (Motrin, Advil).
  • Avoid squeezing or picking the blister.
  • Apply ice to ease the pain.
  • Acidophilus pills may be helpful in treating cold sores. L-lysine is an amino acid widely advertised to treat cold sores. Conflicting medical opinions exist about its effectiveness.

Nutritional concerns

If children are prone to recurrent viral infections, parents should review their eating habits. The children should avoid foods and drinks that are proven suppressors of immunity (foods high in sugar, caffeine , and alcohol content) and have regular meals with plenty of fresh vegetables and fruits and whole-grain products. Some foods may be increased or reduced for specific types of viral infections. For herpes, foods containing the amino acid arginine (nuts and seeds) need to be reduced, and those containing the amino acid lysine (yogurt and cottage cheese) need to be increased. Immune system health in children can also benefit from a wide range of vitamins and minerals as nutritional supplements. Vitamin B complex and vitamins A, C, and E are the most important supplements.


Anyone can become infected with the herpes virus. Once infected, the virus remains latent in the body for life. It lives in nerve cells where the immune system cannot find it. The herpes virus lies dormant in the nerves of the face and is reactivated by sunburn, a recent viral illness (cold or flu), and periods of stress. Cold sores spread from person to person by direct skin-to-skin contact.

The highest risk for spreading the virus is the time period beginning with the blisters and ending with scab formation. However, infected people need not have visible blisters to spread the infection since the virus may be present in the saliva without obvious oral lesions.

Most children experience fewer than two recurrent outbreaks of cold sores each year; some have frequent outbreaks and others never experience outbreaks. Most blisters form in the same area each time and are triggered by the same reasons (such as stress, sun exposure, etc.).


Cold sores are contagious. As of 2004 there were no herpes vaccines available, although herpes vaccines were in research and development. Avoiding close contact with people shedding the virus is the best way to prevent primary herpes. Several practices can reduce reoccurring cold sores and the spread of virus:

  • Parents should teach children not to share drinks, food, or eating utensils, and not to exchange kisses with someone with mouth sores.
  • When parents have an outbreak, they should avoid kissing their children (and other adults).
  • Parents should be watchful of infected children and not allow them to share toys that may be put into the mouth. Toys that have been in the child's mouth should be disinfected before other children play with them.
  • Parents should be especially careful with infants; they should not kiss the eyes or lips of a baby who is under six months old. The child's eyes and genitals are particularly susceptible to the herpes virus. They should keep the child from picking at a cold sore as much as possible.
  • To keep from spreading the infection to other parts of the child's body or giving the virus to someone else, parents and caregivers should wash their hands and the child's hands often, especially after feedings and diaper changes.
  • The child should be protected from the sun, since exposure to sunlight can trigger an outbreak. If the child is outside on a sunny day, generously apply sunscreen and lip balm that contains sun block before prolonged exposure to the sun. Sun block should be used during both winter and summer months, to help prevent cold cores. Wearing a hat with a large brim is also helpful.
  • Parents should wear gloves when applying ointment to a child's sore. They should remove gloves and wash hands before and after changing diapers.
  • Antibiotic ointments may be used to treat secondary bacterial infection of lesions. Parent should avoid using steroid creams or gels on a suspected herpes infection because these agents could make the infection worse.
  • Parents should maintain good general health. A healthy diet, plenty of sleep, and exercise help to minimize the chance of getting a cold or the flu, which may bring on cold sores. Also, good general health keeps the immune system strong; this helps to keep the virus in check and prevents outbreaks.

Parental concerns

The child with a herpes infection is usually miserable and needs generous cuddling and comfort in spite of the infection. Parents of children who get cold sores should be aware of early symptoms and be ready to treat the sore in the first couple days. They should also keep in mind the prevention tips mentioned above. Parents should call the child's pediatrician if the child has not had a cold sore before, especially in the case of babies.


Antiviral drug —A medication that can destroy viruses and help treat illnesses caused by them.

Contagious —The movement of disease between people. All contagious disease is infectious, but not all infections are contagious.

Herpetic gingivostomatitis —A severe oral infection that affects children under five years of age; vesicles and ulcerations, edematous throat, enlarged painful cervical lymph nodes occur; chills, fever, malaise, bed breath, and drooling.

Latent virus —A nonactive virus that is in a dormant state within a cell. The herpes virus is latent in the nervous system.

Oral lesions —A single infected sore in the skin around the mouth or mucus membrane inside of the oral cavity.

Prodrome —Early symptoms that warn of the beginning of disease. For example, the herpes prodrome consists of pain, burning, tingling, or itching at a site before blisters are visible while the migraine prodrome consists of visual disturbances.

Recurrence —The return of an active infection following a period of latency.

Reye's syndrome —A serious, life-threatening illness in children, usually developing after a bout of flu or chickenpox, and often associated with the use of aspirin. Symptoms include uncontrollable vomiting, often with lethargy, memory loss, disorientation, or delirium. Swelling of the brain may cause seizures, coma, and in severe cases, death.

Secretion —A substance, such as saliva or mucus, that is produced and given off by a cell or a gland.



Health and Healing the Natural Way: Energize Your Life. Pleasantville, New York: The Reader's Digest Association, Inc., 2000.

Parker, Philip M., et al. Cold Sores: A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References. Boulder, CO: netLibrary, 2003.


Novatnack, Ellen, and Steven Shchweon. "Herpes: A bigger problem than you think." RNMagazine 65 (June 2002):31-37.


"Herpes labialis (oral Herpes simplex)." MedlinePlus , July 12, 2004. Available online at (accessed December 14, 2004).

Aliene S. Linwood, RN, DPA, FACHE Belinda Rowland, PhD

User Contributions:

hannah xuereb
my daughter is 15 months old she had coldsores come up about 3 months ago and ended up in hospital she evently got better. They have come up again been to the doctors they gave her zarvirax its been about a week her temp has gone as high as 40.2 keep giving her fluids as she is not eating i am worried as she is small for her age anyway do u have any suggestions?
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