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Clinical Reference Systems: Pediatric Advisor 10.0

Cold Sores (Fever Blisters) (for Teenagers)


  • a cluster of painful 1- to 3-mm bumps or blisters on the outer lip
  • on one side of the mouth only
  • tingling or burning on the outer lip at the same site where cold sores previously occurred.


Cold sores are caused by the herpes simplex virus (usually Type 1). The first bout follows contact with someone with herpes. Thereafter, the cold sores recur in 2 percent of people when the virus (which lives in the sensory nerve) is reactivated by sunburn, fever, friction, or physical exhaustion.


The blisters will rupture, scab over, and dry up. The whole process takes 10 to 14 days. The sores do not cause scars. Treatment can shorten the course by many days.


  1. Antiviral ointment

    Once you get fever blisters, you usually can't shorten the time that you have them unless you start applying an antiherpes ointment as soon as any small bumps appear. These ointments require a prescription. If you don't have an antiherpes ointment, cover the fever blisters with petroleum jelly to reduce the pain and to promote healing.

    You need the ointment prescribed by your physician. The ointment can reduce the severity of the sores only if treatment is started early.

  2. Prevention

    Since fever blisters are often triggered by exposure to intense sunlight, prevent them in the future by using a lip balm containing sunscreen. If blisters are not yet present, apply an ice cube or ice pack to the tingly area continuously for 90 minutes. This will sometimes abort the infection.

    Avoid spreading this germ to another person's eye, because an infection there can be serious. Therefore, don't picking at the sore, and wash your hands frequently. Since the condition is contagious, avoid kissing other people during this time.

    If you are going skiing or to the beach and have had frequent herpes flareups in the past, despite careful use of sunscreen, call your physician. Recent research has found that starting oral antiherpes medication (pills) before such outings can prevent most flareups.


  • Any sores occur near the eye.
  • The sores last longer than 2 weeks.
  • You have questions about antiherpes ointments.
  • You have other concerns or questions.

Written by B.D. Schmitt, M.D., author of "Your Child's Health," Bantam Books.
Copyright 1999 Clinical Reference Systems