Cold sores are small, blister-like lesions that usually appear around the mouth. They are caused by the herpes simplex viruses. The strain that usually causes them around the mouth is herpes simplex type 1 (HSV-1).

In rare cases, cold sores can also be caused by the herpes simplex type 2 virus (HSV-2). This can happen as a result of having oral sex with a man or woman who has genital herpes.

The herpes simplex virus

The herpes simplex virus, or ‘cold sore virus’, is highly contagious and can be easily passed from person to person by close direct contact. Once someone has been exposed to the virus, it remains dormant (inactive) most of the time.

However, every so often the virus is activated by certain triggers, causing an outbreak of cold sores. The triggers that cause cold sores vary from person to person. Some people have frequently recurring cold sores, two to three times a year for example, while others have one cold sore and never have another. Some people never get cold sores because the virus never becomes active.

Outlook

Cold sores usually clear up without treatment in 7 to 10 days and do not leave a scar.

Creams and treatments are available over the counter that may help ease the symptoms and speed up the healing time. To be effective, these treatments must be applied as soon as you have signs of a cold sore, such as a burning or tingling sensation.

In most cases, cold sores are mild. In rare cases, they can cause a number of complications.

In newborn babies or people with weakened immune systems, cold sores can be life threatening, although this is rare.