COLD SORE
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A cold sore is a fluid-filled, painful
blister which is usually on or around the lips. Other names for a
cold sore are fever blister, oral herpes, labial herpes, herpes
labialis, and herpes febrilis. Cold sores most often occur on the
lips which distinguishes them from the common canker sore which is
usually inside the mouth. Cold sores do not usually occur inside the
mouth except during the initial episode. Canker sores usually form
either on the tongue or inside the cheeks.
Cold sores are caused by a herpes virus. There are eight different
kinds of human herpes viruses. Only two of these, herpes simplex,
types 1 and 2, can cause cold sores. It is commonly believed that
herpes simplex virus type 1 infects above the waist and herpes
simplex virus type 2 infects below the waist. This is not completely
true. Both herpes virus type 1 and type 2 can cause herpes lesions
on the lips or genitals but recurrent cold sores are almost always
type 1.
Oral herpes is very common. More than 60% of Americans have had a
cold sore and almost 25% of those infected experience recurrent
outbreaks. Most of these persons became infected before age 10.
Anyone can become infected by herpes virus and once infected, the
virus remains latent for life. Herpes viruses are spread from person
to person by direct skin-to-skin contact. The highest risk for
spreading the virus is the time period beginning with the appearance
of blisters and ending with scab formation. However, infected
persons need not have visible blisters to spread the infection to
others since the virus may be present in the saliva without obvious
oral lesions.
Viruses are different from bacteria. While bacteria are independent
and can reproduce on their own, viruses enter human cells and force
them to make more virus. The infected human cell is usually killed
and releases thousands of new viruses. The cell death and resulting
tissue damage causes the actual cold sores. In addition, herpes
virus can infect a cell and instead of making the cell produce new
viruses, it hides inside the cell and waits. Herpes virus hides in
the nervous system. This is called "latency." A latent virus can
wait inside the nervous system for days, months, or even years. At
some future time, the virus "awakens" and causes the cell to produce
thousands of new viruses which causes an active infection.
This process of latency and active infection is best understood by
considering the cold sore cycle. An active infection is obvious
because cold sores are present. The first infection is called the
"primary" infection. This active infection is then controlled by the
body's immune system and the sores heal. In between active
infections the virus is latent. At some point in the future, latent
viruses become activated and once again cause sores. These are
called "recurrent" infections. Although it is unknown what triggers
latent virus to activate, several conditions seem to bring on
infections. These include stress, illness, tiredness, exposure to
sunlight, menstruation, fever, and diet. |
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| COLD SORE RELATED ITEMS |
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