What causes cold sores? Cold sores are caused by Herpes simplex virus (HSV). There are two types of HSV, type I is the common cause of oral “cold sores.” Type II infections occur mainly below the waist, leading to genital herpes. Herpes infections have a tendency to recur in more or less the same place. Such recurrences may happen often (for example, once a month) or only occasionally (for example, once or twice a year). What makes herpes (cold sores) recur? After infection, the virus enters the nerve cells and lays quietly in a stage that is referred to as “dormant”. At times, the virus can start replicating again and travel down the nerve to the skin, causing sores and blisters. The exact mechanism behind this is not clear, but it is known that some conditions precipitate recurrences, including:

1. Fever, Cold or Flu.
2. Ultraviolet radiation (sun exposure)
3. Stress.
4. Changes in the immune system.
5. Trauma to the skin. 6. Sometimes there is no apparent cause of the recurrence.

How is oral herpes spread? Infections caused by HSV are contagious. The virus is spread from person to person by close contact with herpetic lesions.