Cold Sore (Child)

A cold sore (also called fever blister) is a common viral infection around the lips. It is caused by the herpes simplex virus. It spreads easily from person to person. People are often first exposed to the virus in childhood. Not everyone who has the virus will develop a cold sore, however.

A cold sore starts as one or more painful blisters on the lip or inside the mouth. The blisters break open and crust. They usually go away within 1 week. When your child has his or her first cold sore, he or she may also have a fever and mouth and throat pain. After the cold sore goes away, it can come back on the same spot. This is because the virus stays in the body. After the first "outbreak," though, other symptoms such as fever are usually mild or don't come back.

The frequency of cold sores varies with each child. Some will never have another one. Others will have several per year. Some things that can trigger a cold sore to come back include:

  • Emotional stress

  • Another illness (cold, flu, or fever)

  • Heavy sun exposure

  • Overexertion and fatigue

  • Menstruation

Cold sores can be spread to other people. A child can start spreading the virus from the cold sore a few days before the sore appears. The sore remains contagious until it has gone.

Rarely, the virus can spread to other parts of the body, such as the lungs or the brain.

Home care

  • If your child has been prescribed medicines, give these as the healthcare provider directs. You may use over-the-counter medicine as directed based on age and weight for fever or discomfort. Aspirin should never be used in anyone younger than age 18 who is ill with a fever. It may cause severe disease or death. If your child has chronic liver or kidney disease or ever had a stomach ulcer or gastrointestinal bleeding, talk with your   child's healthcare provider before using these medicines.

  • Appling petroleum jelly to a sore with a disposable cotton swab may help ease pain. Ask your child's healthcare provider before using any other creams or ointments. 

  • For severe pain, wrap an ice cube in a cloth and have your child apply it to the sore for a few minutes at a time. Older children may rinse the mouth with a glass of warm water mixed with a teaspoon of baking soda to relieve pain.

  • Don't give your child acidic foods (citrus fruits and tomatoes).

  • Teach your child not to touch the cold sore. The virus can cause a sore on the finger. It is especially important that the child does not touch the sore then touch his or her eyes. The virus can spread to the eyes.

  • When your child has a cold sore, make sure your child:

    • Washes his or her hands often

    • Doesn't kiss others

    • Doesn't share utensils, towels, or toothbrushes

  • Clean your child's toys with a disinfectant.

  • Have your child wear a hat and use sunblock on his or her lips before going out in the sun.

  • Children with open draining lip sores should stay out of school or daycare until the sore forms a scab.

Follow-up care

Follow up with the child's healthcare provider as advised by our staff.

When to seek medical advice

Call the child's healthcare provider right away for any of the following:

  • Eye pain, redness, or drainage from the eye

  • Inability to eat or drink due to pain

  • Headache

  • Increasing cough

Call 911

Call 911 or get immediate medical care if any of the following occur:

  • Unusual irritability

  • Drowsiness

  • Confusion

  • Stiff neck

  • Seizure

  • Trouble breathing

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