Cold Sores: Common and Contagious

What Are Cold Sores?

In the mirror this morning, you may have faced the unwelcome but familiar sight of small, fluid-filled blisters around or in your mouth. Often called fever blisters or cold sores, they are the mark of a common and highly contagious viral disease—oral herpes.

While many people think of herpes as a sexually transmitted disease, the virus that causes cold sores is a different strain of the one that causes genital herpes. The oral herpes virus is also related to the viruses that cause infectious mononucleosis, chicken pox, and shingles.

Canker Sores Are Not Cold Sores

If a canker sore appears inside your mouth, you may find it difficult to distinguish it from a cold sore. Canker sores are not caused by the oral herpes virus, and the treatment is different. Canker sores—tiny, shallow ulcers that cause mouth pain for about five to 10 days—usually occur on the tongue or inside the lips or cheeks. Research suggests that canker sores develop as a response to a localized trauma or irritation. Unlike cold sores, canker sores are not contagious and may be treated with a steroid ointment.

A Familiar Childhood Infection

Oral herpes typically appears first in early childhood. In fact, at least 70 percent of youngsters under the age of 14 may carry the virus. Once infected, a person carries oral herpes indefinitely. In many carriers, however, the virus stays dormant in the body and does not cause problems. Children often contract the oral herpes virus through direct contact with someone who has cold sores, often by kissing or sharing eating utensils. The tendency of toddlers to put everything in their mouths makes them more likely to catch the virus. But because carriers with no symptoms can also transmit the infection, you cannot prevent every case of oral herpes—no matter how careful you are. Even so, you can minimize your children's risk of catching or spreading oral herpes by taking these precautions:

Do not allow people with cold sores to kiss your children.
Discourage children from sharing eating utensils, lip balm, and towels.
Keep children at home when they have cold sores.
Make sure that your child's dentist or hygienist sterilizes all instruments before using them.

Many children contract the oral herpes virus without showing obvious signs of illness. With other children, however, symptoms resembling those of a strep infection or infectious mononucleosis appear from two to 20 days after being exposed to the virus. Symptoms of a first-time oral herpes infection may include the following:

a blister or cluster of blisters on the lips, tongue, floor, or roof of the mouth
oral pain or irritation
sore throat
swollen gums and lips
headache
chills
mild fever
enlarged glands
poor appetite

Call your child's health care provider if you suspect that the child has oral herpes. Treatment to reduce the child's discomfort may include rest, non-acidic cool drinks such as apple or apricot juice, mild pain relievers, and prescription ointments, mouth rinses, or gargles. Avoid using creams and ointments containing cortisone or other steroids, because these preparations may spread an oral herpes infection.

The fever and pain of a first outbreak may last up to one week. The irregularly shaped sores that appear after the blisters burst may take as long as two weeks to disappear completely.

Recurring Cold Sores

Some people suffer recurrent cold sore outbreaks. These subsequent infections, which may be occasional or frequent, tend to be milder than first outbreaks. They also last a shorter time, usually a week to 10 days in total.

A recurrence of cold sores may not be related to any known cause, but many people report that their outbreaks usually follow one or more of the following:

exposure to sunlight
sunburn
fever or infection
mouth injury
allergy
menstruation
emotional stress or fatigue

While you cannot control everything that might cause your cold sores to recur, you may be able to prevent or shorten repeated outbreaks by taking certain precautions:

Since cold sores frequently follow exposure to bright sunlight, use lip balm with sunscreen regularly. If you still have frequent flare-ups even after using sunscreen, ask your health care provider whether you should take an oral anti-herpes medicine before spending a lot of time at the beach or other sunny place.
Cold sores usually return in the same location in or around your mouth. At that spot, you may notice reddened skin or feel a burning or tingling sensation. If these warning signs occur, applying a wrapped ice cube or ice pack to the area for 90 minutes may prevent cold sores from erupting.

Left untreated, recurring cold sore blisters usually rupture, scab over, and then dry up in about 10 days. Medical treatment may shorten this course. As soon as the blisters appear, try applying a prescription anti-herpes ointment to help them disappear faster. Covering the blisters with petroleum jelly also may reduce pain and promote healing.

Prevent Cold Sores From Spreading

Cold sores represent more of an annoyance than a serious health threat, but in rare cases, oral herpes may be dangerous. For example, if the virus spreads to the eyes, infection and permanent scarring may occur.

To protect yourself and others from cold sores, take the following important precautions:

If you feel tingling, burning, itching, or tenderness in a place where you have previously had an oral herpes infection, keep that part of your body away from other people.
Don't squeeze, pinch, or pick at cold sore blisters.
Wash your hands carefully after touching cold sores, particularly before touching another person, your eyes or your genitals.
Call your health care provider if cold sores spread, appear near the eyes or genitals, or last longer than two weeks. Also call with any questions about anti-herpes medicines.