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

The most common cause of cold sores is the virus called 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's 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 again. The cold sores usually don't last longer than a few days, or up to 2 weeks. Hot sun, cold wind, illness, stress, menstrual periods, or a weak immune system can cause cold sores to occur.

A child is more at risk for cold sores if they live with someone infected with the herpes simplex virus.

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 their doctor for a diagnosis.

The doctor will ask about your child's symptoms and health history and give your child a physical exam. A doctor 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 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 is a lifelong infection. Therefore it can't be completely eliminated from the body by treatment, but the treatment may help ease some cold sore symptoms and help these to resolve sooner. 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 doctors about the risks, benefits, and possible side effects of all medicines. Cold sores usually don't scar. They last 3 to 14 days, depending on how extensive they are.

In the vast majority of children, cold sores are annoying and painful but don't cause complications or serious consequences. In rare 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.

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

If your child has a cold sore, make sure they do not:

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

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

Sun protection can help prevent future cold sore breakouts. Put sunscreen on your child's face and lips. Apply a lip balm that contains sunscreen. And have them wear a hat with a brim.

Reducing stress can also help to reduce outbreaks.

Antiviral medicine given daily may be used to prevent outbreaks if they are frequent. Talk to your child's doctor if this is the case.

Contact the doctor if your child has:

• Symptoms that don't get better, or get worse
• Sores near the child's eyes
• New symptoms
• Symptoms that don't go away within 2 weeks
• Frequent outbreaks of cold sores occurring every 1 to 2 months

• 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 complications. Rarely, 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 they don't kiss, share cups or utensils, share washcloths or towels, or touch the cold sore.
• Antiviral and other prescription medicines may be prescribed if the outbreak is particularly bothersome or there are frequent recurrences.

Tips to help you get the most from a visit to your child's doctor:

• 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 doctor 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 doctor after office hours. This is important if your child becomes ill and you have questions or need advice.