Fever Blisters and Canker Sores
National Institute of Dental and
Craniofacial Research
Fever Blisters and Canker
Sores
Fever blisters and canker sores are two of the most common
disorders of the mouth, causing discomfort and annoyance to millions of
Americans. Both cause small sores to develop in or around the mouth, and often
are confused with each other. Canker sores, however, occur only inside
the mouth--on the tongue and the inside linings of the cheeks, lips and throat.
Fever blisters, also called cold sores, usually occur outside the
mouth--on the lips, chin, cheeks or in the nostrils. When fever blisters do
occur inside the mouth, it is usually on the gums or the roof of the mouth.
Inside the mouth, fever blisters are smaller than canker sores, heal more
quickly, and often begin as a blister.
Both canker sores and fever blisters have plagued mankind
for thousands of years. Scientists at the
National Institute of Dental and Craniofacial Research, one of the federal
government's National Institutes of Health,
are seeking ways to better control and ultimately prevent these and other oral
disorders.
Fever Blisters
In ancient Rome, an epidemic of fever blisters
prompted Emperor Tiberius to ban kissing in public ceremonies. Today
fever blisters still occur in epidemic proportions. About 100 million
episodes of recurrent fever blisters occur yearly in the United States
alone. An estimated 45 to 80 percent of adults and children in this
country have had at least one bout with the blisters. |
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What causes fever blisters?
Fever blisters are caused by a contagious virus called
herpes simplex. There are two types of herpes simplex virus. Type 1 usually
causes oral herpes, or fever blisters. Type 2 usually causes genital herpes.
Although both type 1 and type 2 viruses can infect oral tissues, more than 95
percent of recurrent fever blister outbreaks are caused by the type 1 virus.
Herpes simplex virus is highly contagious when fever
blisters are present, and the virus frequently is spread by kissing. Children
often become infected by contact with parents, siblings or other close relatives
who have fever blisters.
A child can spread the virus by rubbing his or her cold
sore and then touching other children. About 10 percent of oral herpes
infections in adults result from oral-genital sex with a person who has active
genital herpes (type 2). These infections, however, usually do not result in
repeat bouts of fever blisters.
Most people infected with the type 1 herpes simplex virus
became infected before they were 10 years old. The virus usually invades the
moist membrane cells of the lips, throat or mouth. In most people, the initial
infection causes no symptoms. About 15 percent of patients, however, develop
many fluid-filled blisters inside and outside the mouth 3 to 5 days after they
are infected with the virus. These may be accompanied by fever, swollen neck
glands and general aches. The blisters tend to merge and then collapse. Often a
yellowish crust forms over the sores, which usually heal without scarring within
2 weeks.
The herpes virus, however, stays in the body. Once a
person is infected with oral herpes, the virus remains in a nerve located near
the cheekbone. It may stay permanently inactive in this site, or it may
occasionally travel down the nerve to the skin surface, causing a recurrence of
fever blisters. Recurring blisters usually erupt at the outside edge of the lip
or the edge of the nostril, but can also occur on the chin, cheeks, or inside
the mouth.
The symptoms of recurrent fever blister attacks usually
are less severe than those experienced by some people after an initial
infection. Recurrences appear to be less frequent after age 35. Many people who
have recurring fever blisters feel itching, tingling or burning in the lip 1 to
3 days before the blister appears.
What causes a recurrence of fever
blisters?
Several factors weaken the body's defenses and trigger an
outbreak of herpes. These include emotional stress, fever, illness, injury and
exposure to sunlight. Many women have recurrences only during menstruation. One
study indicates that susceptibility to herpes recurrences is inherited. Research
is under way to discover exactly how the triggering factors interact with the
immune system and the virus to prompt a recurrence of fever blisters.
What are the treatments for fever
blisters?
Currently there is no cure for fever blisters. Some
medications can relieve some of the pain and discomfort associated with the
sores, however. These include ointments that numb the blisters, antibiotics that
control secondary bacterial infections, and ointments that soften the crusts of
the sores.
Is there a vaccine for fever blisters?
Currently there is no vaccine for herpes simplex virus
available to the public. Many research laboratories, however, are working on
this approach to preventing fever blisters. For example, scientists at the
National Institute of Dental and
Craniofacial Research and the National
Institute of Allergy and Infectious Diseases have developed a promising
experimental herpes vaccine. In tests on laboratory mice, the vaccine has
prevented the herpes simplex virus from infecting the animals and establishing
itself in the nerves.
Although these findings are encouraging, the scientists
must complete more animal studies on the safety and effectiveness of the vaccine
before a decision can be made whether to test it in humans. The vaccine would be
useful only for those not already infected with herpes simplex virus.
What can the patient do?
If fever blisters erupt, keep them clean and dry to
prevent bacterial infections. Eat a soft, bland diet to avoid irritating the
sores and surrounding sensitive areas. Be careful not to much the sores and
spread the virus to new sites, such as the eyes or genitals. To make sure you do
not infect others, avoid kissing them or touching the sores and then touching
another person.
There is good news for people whose fever blister
outbreaks are triggered by sunlight. Scientists at the
National Institute of Dental and
Craniofacial Research have confirmed that sunscreen on the lips can prevent
sun-induced recurrences of herpes. They recommend applying the sunscreen before
going outside and reapplying it frequently during sun exposure. The researchers
used a sunblock with a protection factor of 15 in their studies.
Little is known about how to prevent recurrences of fever
blisters triggered by factors other than sunlight. People whose cold sores
appear in response to stress should try to avoid stressful situations. Some
investigators have suggested adding lysine to the diet or eliminating foods such
as nuts, chocolate, seeds or gelatin. These measures have not, however, been
proven effective in controlled studies.
What research is being done?
Researchers are working on several approaches to
preventing or treating fever blisters. As mentioned earlier, they are trying to
develop a vaccine against herpes simplex virus. Several laboratories are
developing and testing antiviral drugs designed to hamper or prevent fever
blister outbreaks. Researchers also are trying to develop ointments that make it
easier for antiviral drugs to penetrate the skin.
Acyclovir is an antiviral drug that prevents the herpes
simplex virus from multiplying. The U.S. Food and
Drug Administration has approved the drug for use in treating genital
herpes, and is considering its approval for use in treating oral herpes.
Researchers have found that acyclovir taken in pill form reduces the
symptoms and frequency of fever blister recurrences in some patients. In one
study, 50 percent of patients who took four acyclovir pills daily for 4 months
had no fever blister outbreaks. Before taking the drug, they had an average of
one recurrence every 2 months. In separate studies, pills taken at the onset of
symptoms or acyclovir cream applied to the blisters or to areas of the lip that
tingled or itched were found to be only minimally effective. The long-term
effects of daily oral doses of acyclovir are not known, nor are the effects the
drug might have on an unborn child.
Basic research on how the immune system interacts with
herpes simplex viruses may lead to new therapies for fever blisters. The immune
system uses a wide array of cells and chemicals to defend the body against
infections. Scientists are trying to identify the immune components that prevent
recurrent attacks of oral herpes.
Scientists are also trying to determine the precise form
and location of the inactive herpes virus in nerve cells. This information might
allow them to design antiviral drugs that can attack the herpes virus while it
lies dormant in nerves.
In addition, researchers are trying to understand how
sunlight, skin injury and stress can trigger recurrences of fever blisters. They
hope to develop methods for blocking reactivation of the virus.
Canker Sores
Recurrent canker sores afflict about 20 percent of
the general population. The medical term for the sores is aphthous
stomatitis.
Canker sores are usually found on the movable parts of the mouth such as
the tongue or the inside linings of the lips and cheeks. They begin as
small oval or round reddish swellings, which usually burst within a day.
The ruptured sores are covered by a thin white or yellow membrane and
edged by a red halo. Generally, they heal within 2 weeks. Canker sores
range in size from an eighth of an inch wide in mild cases to more than
an inch wide in severe cases. Severe canker sores may leave scars. Fever
is rare, and the sores are rarely associated with other diseases.
Usually a person will have only one or a few canker sores at a time. |
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Most people have their first bout with canker sores
between the ages of 10 and 20. Children as young as 2, however, may develop the
condition. The frequency of canker sore recurrences varies considerably. Some
people have only one or two episodes a year, while others may have a continuous
series of canker sores.
What causes canker sores?
The cause of canker sores is not well understood. More
than one cause is likely, even for individual patients. Canker sores do not
appear to be caused by viruses or bacteria, although an allergy to a type of
bacterium commonly found in the mouth may trigger them in some people. The sores
may be an allergic reaction to certain foods. In addition, there is research
suggesting that canker sores may be caused by a faulty immune system that uses
the body's defenses against disease to attack and destroy the normal cells of
the mouth or tongue.
British studies show that, in about 20 percent of
patients, canker sores are due partly to nutritional deficiencies, especially
lack of vitamin B12, folic acid and iron. Similar studies performed in the
United States, however, have not confirmed this finding. In a small percentage
of patients, canker sores occur with gastrointestinal problems, such as an
inability to digest certain cereals. In these patients, canker sores appear to
be part of a generalized disorder of the digestive tract.
Female sex hormones apparently play a role in causing
canker sores. Many women have bouts of the sores only during certain phases of
their menstrual cycles. Most women experience improvement or remission of their
canker sores during pregnancy. Researchers have used hormone therapy
successfully in clinical studies to treat some women.
Both emotional stress and injury to the mouth can trigger
outbreaks of canker sores, but these factors probably do not cause the disorder.
Who is susceptible?
Women are more likely than men to have recurrent canker
sores. Genetic studies show that susceptibility to recurrent outbreaks of the
sores is inherited in some patients. This partially explains why the disorder is
often shared by family members.
What are the treatments for canker sores?
Most doctors recommend that patients who have frequent
bouts of canker sores undergo blood and allergy tests to determine if their
sores are caused by a nutritional deficiency, an allergy or some other
preventable cause. Vitamins and other nutritional supplements often prevent
recurrences or reduce the severity of canker sores in patients with a
nutritional deficiency. Patients with food allergies can reduce the frequency of
canker sores by avoiding those foods.
There are several treatments for reducing the pain and
duration of canker sores for patients whose outbreaks cannot be prevented. These
include numbing ointments such as benzocaine, which are available in drug stores
without a prescription. Anti-inflammatory steroid mouthrinses or gels can be
prescribed for patients with severe sores.
Mouthrinses containing the antibiotic tetracycline may
reduce the unpleasant symptoms of canker sores and speed healing by preventing
bacterial infections in the sores. Clinical studies at the
National Institute of Dental and
Craniofacial Research have shown that rinsing the mouth with tetracycline
several times a day usually relieves pain in 24 hours and allows complete
healing in 5 to 7 days. The U.S. Food and Drug
Administration warns, however, that tetracycline given to pregnant women and
young children can permanently stain youngsters' teeth. Both steroid and
tetracycline treatments require a prescription and care of a dentist or
physician.
Patients with severe recurrent canker sores may need to
take steroid or other immuno-suppressant drugs orally. These potent drugs can
cause many undesirable side effects, and should be used only under the close
supervision of a dentist or physician.
What can the patient do?
If you have canker sores, avoid abrasive foods such as
potato chips that can stick in the cheek or gum and aggravate the sores. Take
care when brushing your teeth not to stab the gums or cheek with a toothbrush
bristle. Avoid acidic and spicy foods. Canker sores are not contagious, so
patients do not have a worry about spreading them to other people.
What research is being done?
Researchers are trying to identify the malfunctions in
patients' immune systems that make them susceptible to recurrent bouts of canker
sores. By analyzing the blood of people with and without canker sores,
scientists have found several differences in immune function between the two
groups. Whether these differences cause canker sores is not yet known.
Researchers also are developing and testing new drugs
designed to treat canker sores. Most of these drugs alter the patients' immune
function. Although some of the drugs appear to be effective in treating canker
sores in some patients, the data are still inconclusive. Until these drugs are
proven to be absolutely safe and effective, they will not be available for
general use.
Public Information and Reports Section
Office of Planning, Evaluation and Communications
National Institute of Dental Research
Bethesda, Maryland 20892
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
Public Health Service
National Institutes of Health
NIH Publication No. 92-247
Revised July 1992
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