Overview

Cold sores are small blisters around the mouth caused by the herpes simplex virus. They are sometimes called fever blisters. 

Causes

The most common strain of the virus that causes cold sores is herpes simplex virus 1. The herpes simplex virus in a cold sore is contagious. It can be spread to others by kissing, sharing cups or utensils, sharing washcloths or towels, or by touching the cold sore before it is healed. The virus can also be spread to others 24 to 48 hours before the cold sore appears. 

Once a child is infected with the herpes simplex virus, the virus becomes inactive (dormant) for long periods of time. It can then become active at any time and cause cold sores. The cold sores usually don't last longer than 2 weeks. Hot sun, cold wind, illness, or a weak immune system can cause cold sores to occur.

Risk Factors

A child is more at risk for cold sores if he or she lives with someone infected with the herpes simplex virus.

Symptoms

Symptoms can occur a bit differently in each child. Some children don’t have symptoms with the first infection of herpes simplex virus. In other cases, a child may have severe flu-like symptoms and ulcers in and around the mouth. When cold sores come back after the first infection, symptoms are usually not as severe. The most common symptoms of cold sores include:

  • A small blister or group of blisters on the lips and mouth that get bigger, leak fluid, then crust over
  • Tingling, itching, and irritation of the lips and mouth
  • Soreness of the lips and mouth that may last from 3 to 7 days

The symptoms of cold sores can be like other health conditions. Make sure your child sees his or her healthcare provider for a diagnosis.

Diagnosis

The healthcare provider will ask about your child’s symptoms and health history. He or she will give your child a physical exam. A healthcare provider can usually diagnose your child by looking at the sores. Your child may also have tests, such as:   

  • Skin scrapings. The sores are gently scraped to remove tiny samples. The samples are examined to look for the virus.
  • Blood tests. These are to check for signs of virus in the blood.

Treatment

Treatment will depend on your child’s symptoms, age, and general health. It will also depend on how severe the condition is.

The herpes simplex virus infection that causes cold sores can’t be cured, but treatment may help ease some cold sore symptoms. Treatment may include antiviral medicine and other types of prescription medicines. These medicines work best if started as soon as possible after the first sign of a herpes infection or recurrence. Talk with your child’s healthcare providers about the risks, benefits, and possible side effects of all medicines.

Complications

In most children, cold sores don't cause serious illness. In some cases, the herpes simplex virus can cause inflammation of the brain (encephalitis). This is a serious illness and needs to be treated right away. It can lead to long-term problems of the brain.

Cold sores in a newborn baby can cause serious illness and death. This may be the case even when treated with medicine.

Prevention

If someone in your household has herpes simplex, you can protect your child by making sure he or she is not exposed. Keep in mind that the virus may be in saliva even when there are no cold sores. Make sure your child doesn’t kiss, share cups or utensils, or share washcloths or towels with the person. Make sure your child doesn’t touch a cold sore.

If your child has a cold sore, make sure he or she does not:

  • Touch or rub the cold sore
  • Share cups or eating utensils
  • Share wash cloths or towels
  • Kiss others

The healthcare provider may advise keeping your child home from school during the first infection of herpes simplex virus.

Living with

Sun protection can help prevent future cold sore breakouts. Put sunscreen to your child’s face and lips. Have him or her wear a hat with a brim.

When to Call a Healthcare Provider

Call the healthcare provider if your child has:

  • Symptoms that don’t get better, or get worse
  • New symptoms

Key Points

  • Cold sores are small blisters around the mouth caused by the herpes simplex virus.
  • The herpes simplex virus in a cold sore is contagious. It can be spread to others by kissing, sharing cups or utensils, sharing washcloths or towels, or by touching the cold sore before it is healed. The virus can also be spread to others 24 to 48 hours before the cold sore appears. 
  • Symptoms include a small blister or group of blisters on the lips and mouth that enlarge, leak fluid, then crust over.
  • In most children, cold sores do not cause serious illness. In some cases, the herpes simplex virus can cause inflammation of the brain (encephalitis). This is a serious illness and needs to be treated right away.
  • If your child has a cold sore, make sure he or she does not kiss, share cups or utensils, share washcloths or towels, or touch the cold sore.

Next Steps

Tips to help you get the most from a visit to your child’s healthcare provider:

  • Know the reason for the visit and what you want to happen.
  • Before your visit, write down questions you want answered.
  • At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you for your child.
  • Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are.
  • Ask if your child’s condition can be treated in other ways.
  • Know why a test or procedure is recommended and what the results could mean.
  • Know what to expect if your child does not take the medicine or have the test or procedure.
  • If your child has a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your child’s provider after office hours. This is important if your child becomes ill and you have questions or need advice.