What are cold sores?


CDC/ Dr. Herrmann

They can appear individually or in clusters. Despite their name, cold sores have nothing to do with colds.

Some people confuse cold sores with canker sores. Canker sores are crater-like sores that usually appear individually on the tongue or gums or on the inside of the cheeks.

What causes cold sores?

Cold sores are caused by the herpes simplex virus. Herpes simplex virus type 1 usually causes cold sores, and herpes simplex virus type 2 usually causes genital herpes, though either can cause sores in the facial or genital area.

How did my child get the virus?

Someone with the virus – most likely in the form of a cold sore or herpes gingivostomatitis – gave it to him. Most people who get the herpes simplex virus get it sometime during childhood.

For example, maybe your child shared a cup, utensil, or slobbery toy with someone who has the infection. Or maybe he was kissed by someone with the virus in her saliva (whether or not the person had a visible sore).

Babies can also get the herpes virus during a vaginal birth if their mother has genital herpes. You can't transmit the virus to your baby by breastfeeding, though, even if you have an active cold sore.

Are there other symptoms?

During the first bout with the herpes simplex virus – called primary herpes – your child may have mouth soreness (the blisters can spread throughout the mouth during this first episode), gum inflammation, and perhaps a fever, swollen lymph nodes, and a sore throat. These primary symptoms may be very mild, and you may not even notice them.

Your child will get better in about 10 to 14 days, but the virus will stay in her body for life. In some people, the virus lies dormant and never acts up. In others, it periodically flares up and triggers cold sores.

These flare-ups are called secondary herpes. Stress, fever, and sun exposure – but not contact with a cold sore – seem to trigger outbreaks.

During these secondary flare-ups, your child probably won't have swelling of her gums or lymph nodes or a fever or sore throat, but she will have the telltale blistering on or near her lips.

Are cold sores ever dangerous?

Cold sores themselves aren't dangerous, but it is possible for the virus to spread to other parts of the body – and that can be dangerous.

It's very unusual for a child to get a cold sore in the first six months or so of life, because the antibodies received from his mother offer some protection. But if your baby is younger than 3 months old and he gets any kind of mouth sore, call his doctor right away. In young babies, in particular, the herpes virus can spread to the brain and other organs, causing serious, potentially permanent or fatal damage.

Try to keep your child from touching his eyes when he has a cold sore. When the virus spreads to the eyes, it's called ocular herpes. This is a serious eye infection.

If your child develops a sore on his eyelid or the surface of his eye, call the doctor right away. Your child may need antiviral drugs to keep the infection from scarring his cornea. In rare cases, ocular herpes can weaken vision and even cause blindness.

What's the best way to treat a cold sore?

A cold sore will go away on its own. Here are some ways to ease any discomfort:

  • Give your child the proper dose of a mild pain reliever, such as acetaminophen or (if she's 6 months or older) ibuprofen. (If your child is younger than 3 months old, call the doctor before giving her any medication. And never give aspirin to a baby. It could trigger Reye's syndrome, a rare but life-threatening illness.)
  • Avoid citrus fruit and other acidic food (such as tomatoes) that might make the sore hurt more.
  • Try over-the-counter ointments to relieve the pain and help heal the cold sore. (If your child is younger than 12 months, check the age recommendations on the package and talk with the doctor about what's best for your child.)
  • If the sore is severe, the doctor may prescribe an antiviral topical or oral medicine.

If your child's cold sore is painful, it may interfere with eating. If that's the case, talk with her doctor right away.

How can I prevent cold sores and keep them from spreading?


If you have a cold sore:

  • Avoid kissing your child, especially if he's a newborn, until the cold sore goes away. If your child is an infant, consider wearing a surgical mask to cover the sore as well.
  • Avoid sharing cups and eating utensils.

If your child has a cold sore:

  • Wash his hands regularly.
  • Try to keep him from picking at the cold sore. (Try putting mittens or socks on his hands while he sleeps.)
  • Don't let him share toys.
  • Don't let him share drinks or eating utensils.
  • Don't let him kiss babies.

Exposure to sunlight can trigger an outbreak once a child has the virus. So if your child seems prone to cold sores as he gets older, sun protection is a particularly good idea. A hat with a brim and some lip balm for protection should help.