Cold sores are oozing blisters that can erupt on any part of the body, although they tend to occur most often on or near the lips or inside the mouth. The herpes simplex virus, which can be transmitted from child to child or parent to child, often through saliva, is responsible for these sores.
The first time your child has a herpes simplex infection, the lesions will typically spread throughout his mouth. Thereafter, the virus itself changes character and lies dormant within the nerve, occasionally reactivating in response to any of a number of triggers, including sunlight, cold, heat, fever, and stress. Just before these new blisters emerge, your child may feel an itching or tingling sensation in the region.
There are antiviral drugs that are effective against herpes simplex virus; these drugs are used for severe infections and for infections in children whose immune systems are not normal. Although these drugs can relieve symptoms and shorten the duration of the illness, they are not cures and do not prevent recurrences. Most children do not need antiviral therapy; topical therapy is not very helpful, and oral therapy must be started very early to be effective. The only therapy needed in most cases of cold sores is symptomatic relief: Many doctors recommend that children keep cold sores moist with lip balm in order to help relieve discomfort. These sores will eventually form scabs and heal, disappearing after seven to fourteen days. Until they are gone, discourage your child from scratching or picking at them. In general, however, there is no need to keep him home from school.