These sores typically appear on the outside of the mouth, on the lips. The majority (about 95 percent) of fever blisters are due to a virus, typically herpes type 1. Because the sores are due to a virus, they're contagious and most people will be exposed to the virus during their lifetime.
Children are typically exposed via contact with an adult, sibling or relative who has a fever blister, or with other children who've mouthed toys or other objects that may have been contaminated with the virus.In many cases, exposure is asymptomatic, while other children will develop painful vesicles appearing both inside the mouth, on the tongue and gums, as well as on the lips 3-5 days after exposure.
This initial illness is called herpetic gingivostomatitis. The initial infection tends to be more uncomfortable and may take up to two weeks to resolve. The most difficult aspect is oral discomfort, so it's important to make sure infected youngsters stay hydrated. Popsicles are often helpful for this.
Once you've been exposed to the herpes virus, it remains in your nerve endings, where it may be dormant and asymptomatic for years. About 60 percent of children are positive for HSV-1 by adolescence. At times of stress, sun exposure, fever, or menstrual periods, the virus may become active again, and result in a fever blister.
Children who develop a fever blister are also contagious and may spread the virus to others by touching them, or picking at the lesion and then touching other people or objects with their mouths.
Fever blisters may be treated in most cases with a topical antiviral applied directly to the lesion. Prescription medications are available that may shorten the duration of a fever blister by a day or two, especially if started early and applied frequently. If you child experiences recurrent core sores, speak with your pediatrician about the use of oral antiviral medications.
Remember, if you have a fever blister, don't kiss your baby! Although the most viral shedding occurs after the initial HSV infection, you remain contagious with each fever blister, so it is best to take precautions for a few days after an outbreak.
(Dr. Sue Hubbard is a nationally known pediatrician and co-host of "The Kid's Doctor" radio show. Submit questions at www.kidsdr.comat www.kidsdr.com.)
