Cold Sores Causes & Risks

Causes

Cold sores are usually caused by the herpes simplex 1 virus. It can sometimes be caused by the herpes 2 virus that causes genital herpes . The two viruses are related, but different. The virus invades the skin, then lies dormant for weeks or months before causing inflammation and blistering.

In most cases, people contract the virus as infants or young children. The first episode of illness with herpes simplex 1 virus causes a systemic illness. Then the virus lies dormant until it is reactivated. This results in painful cold sores. They are usually located at the border of the colored part of the lip.

The virus can be spread by:

• Contact with the fluid from a cold sore of another person, or sores of genital herpes in most cases of the herpes 2 virus
• Contact with the eating utensils, razors, towels, or other personal items of a person with active cold sores
• Sharing food or drink with a person with active cold sores
• Contact with the saliva of a person who has the herpes simplex virus

Risk Factors

Infection with this virus is so common that everyone is considered at risk.

Once the herpes simplex 1 virus is present in the body, the following risk factors can trigger cold sores to form:

• Transplantation
• Malnutrition
• Infection, fever, cold, or other illness
• Exposure to sun
• Physical or emotional stress
• Certain foods or drugs
• Weakened immune system
• Menstruation
• Eczema
• Physical injury or trauma
• Dental or other oral surgery
• Excessive exercise

Cold sores often form without an identifiable trigger.