Cold Sores: What causes them?

My five-month-old baby has a cold sore at the corner of his mouth. How can I treat it and prevent it from spreading?


Robert Steele

Robert W. Steele, MD, is a board certified pediatrician at St. John's Regional Health Center in Springfield, MO. He graduated from medical... Read more

Cold sores, also called fever blisters, are quite common in childhood, affecting thousands of kids (and adults) each year. They are caused by the herpes simplex virus. This name tends to strike fear in the hearts of those who hear it because they recognize it as the virus associated with genital herpes, a sexually transmitted disease. However, these viruses, while similar in name, tend to be distinct types of infections.

Some children acquire the virus but have few, if any, symptoms. Others get the infection and develop many sores in and around the mouth. These blisters can be quite painful and may be associated with low-grade fevers. The children have difficulty swallowing their saliva because of the pain, and they may have a poor appetite; the glands around the neck may swell slightly and become mildly tender. Fortunately, the initial severe infection tends to be a one-time occurrence. Unfortunately, once infected, children become carriers of the virus, which may last a lifetime.

Some children never have another cold sore after the initial infection, while others develop recurrent sores, usually after episodes of stress such as fever, sunburn or injury to the mouth. These sores usually occur in the same spot each time because, after the virus causes the cold sore, it travels back down the nerve to lie dormant deep inside the body. When it becomes reactivated in times of stress, it travels down the same nerve, right back to the spot it infected previously.

Cold sores are contagious by direct contact with the sore itself or the saliva from someone with an active sore. The virus is usually passed from adult to child by kissing or from child to child as they play together. And contact within the mouth can cause one fever blister to spawn another. As children wipe their mouths with their hands, the infection may spread to outside of the mouth or even to the fingers themselves.

For older children or those with particularly severe infections, medications such as acyclovir, valacyclovir and famcyclovir may be options your doctor can prescribe.

However, treatment of oral herpes in children is primarily aimed at the symptoms. Acetaminophen (Tylenol) or ibuprofen (Motrin, Advil, etc.) can be used for pain. In addition, for older children who can "swish-and-spit," a prescription mouth rinse may help. To prevent dehydration, make sure your child gets plenty of "mild" liquids; juices and carbonated beverages can be painful as they touch the sores.

Prevention of cold sores can be difficult because many people are carriers of the virus without even knowing it. However, some common sense can help prevent its transmission. Don't let anyone who has a cold sore kiss your child. If your either your child or his playmate has a cold sore, it's probably best to curtail playtime together until the sore heals.

Please keep in mind that more than 80 percent of people above the age of 20 have been exposed to this virus at some point in their lives. Some get sores and some don't. So, the fact your child has a cold sore does not mean someone has been careless in handling him.

The best way to keep him from spreading the sores to other body parts is to keep his hands out of his mouth. This is obviously easier said than done, but with some creative distraction maneuvers on your part, as well as strategically placed socks over the hands for a couple of days, spread may be prevented.

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