Cold sores (fever blisters) are caused by infection with the Herpes simplex virus. They present as small, painful blisters, which occur on and around the lips, often after exposure to excess sunlight or if the child is ill or emotionally stressed. They usually start with a tingling, itching, burning sensation for a few hours before the painful blister develops. The blister bursts after a few days and then dries, leaving a crust, which disappears in a week or two. The problem with cold sores is that they often recur at the same site. The outbreaks of cold sores usually occur every few months but tend to become less frequent over time.
The management consists of applying povidone iodine (Betadine) ointment or 2% vioform in zinc cream twice daily to prevent bacterial infection. Local antiviral agents are of limited use. In severe cases, oral acyclovir can be used.
Herpes simplex virus, which remains in nerve ganglia, causes recurrent attacks of cold sores. A history of a primary infection of herpes stomatitis with many painful, small ulcers of the mouth and tongue, together with fever, may or may not be obtained. Often the primary infection with herpes virus is asymptomatic. Cold sores typically occur when immunity is depressed.