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Cold Sores (Fever Blisters)

Teen Version

What are cold sores?

Cold sores are a cluster of painful bumps or blisters on the outer lip. They happen only on one side of the mouth. Just before a cold sore develops, you may feel a tingling or burning on the outer lip at the same place where you had cold sores before.

What is the cause?

Cold sores are caused by the herpes simplex virus. The sores happen for the first time after you have had contact with someone with herpes. Thereafter, the virus lives in the sensory nerve and can cause cold sores again. About 20% of adults have recurring cold sores. The sores come back because of sunburn, fever, friction, stress, or physical exhaustion.

How long do cold sores last?

The blisters will rupture, scab over, and dry up. The whole process takes 10 to 14 days. The sores do not cause scars. If started early, treatment with antiviral pills can shorten the course by many days.

How can I take care of myself?

  • Ice

    If you feel tingling in the usual place but the blisters are not yet present, apply an ice cube or ice pack continuously for 30 minutes. This may stop the infection.

  • Cold sores ointment

    Once you get fever blisters, start applying a special cold sore ointment as soon as any small bumps appear. Docosanol (Abreva) is an example of one nonprescription cream. If you don't have a special ointment, cover the fever blisters with petroleum jelly to reduce the pain. Reapply it 4 times a day.

  • Medicines

    Give acetaminophen or ibuprofen for pain relief. Once you get fever blisters, you usually can't shorten the course unless you have antiherpes pills and start them as soon as any small bumps appear. These require a prescription and some health care providers do not approve of them for this purpose. Antiherpes ointments do not shorten the course.

How can cold sores be prevented?

Since fever blisters are often triggered by exposure to intense sunlight, prevent them in the future by using a lip balm containing sunscreen with an SPF of 30.

Avoid spreading this germ to another person's eye, because an infection there can be serious. Therefore, don't pick 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 health care provider. Taking prescription antiherpes pills before such outings can prevent most flareups.

When should I call my health care provider?

Call during office hours if:

  • Any sores occur near the eye.
  • The sores last longer than 2 weeks.
  • You have questions about prescription medicine for herpes.
  • You have other concerns or questions.
Written by B.D. Schmitt, M.D., author of "Your Child's Health," Bantam Books.
Published by McKesson Provider Technologies.
Last modified: 2006-10-12
Last reviewed: 2006-02-23
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Copyright 2006 McKesson Corporation and/or one of its subsidiaries. All Rights Reserved.
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