health

Cold sores are painful blisters that develop on the lips or around the
mouth after a person has become infected with the herpes simplex virus.
The herpes simplex virus 1 (HSV-1) that generally causes cold sores is
related to the herpes simplex virus (HSV-2), that typically causes genital
herpes but can also cause cold sores.
People who become infected with HSV-1 develop cold sores
within twenty days of infection, although some may develop symptoms
sooner. The first episode of infection (called the primary infection)
may not have any symptoms or may cause two to three weeks of
fever and blisters/sores both in and around the mouth. In most cases,
the recurrence of symptoms is preceded by a prodrome, or period of
warning symptoms before the main phase of the illness. The prodrome
of cold sores usually consists of a tingling, itching, or burning sensation
that starts one or two days before the blisters appear. The area of
skin where the blisters will erupt may swell up, turn red, and be sore to
the touch.
The sores themselves last for about a week after they erupt. They
appear most commonly on the lips or the area of skin between the upper
lip and the nose.
The blisters are small and thin-walled, filled with a clear fluid,
and become sores after several days. The HSV-1 virus is shed in the
fluid from the sores and can be transmitted to other people if they
come in contact with the blisters. This is the stage in the development
of cold sores when the infection is most contagious. After a few days,
the ulcers form a yellow crust that eventually drops off, leaving an area
of pinkish skin underneath. There is no permanent scar from a cold
sore. People who get cold sores may have one or two recurrences per
year, although some have an outbreak every month and some never
have relapses.