Herpes simplex is a virus that infects the skin, mucous membranes and nerves.

There are two major types of herpes simplex virus

(HSV). Type I is the most common and primarily infects the face, causing the familiar “cold sore” or “fever blister.” Type II is the sexually transmitted form of herpes, infecting the genitals. While both can spread to the eye and cause infection, Type I is by far the most frequent type associated with herpes simplex eye disease.

Type I herpes is very contagious and commonly is transmitted by skin contact with someone who has the virus. Almost everyone — about 90 percent of the population — is exposed to Type I herpes, usually during childhood.

After the original infection, the virus lies in a quiet or dormant period, living in nerve cells of the skin or eye.

Occasionally, the virus can reactivate and cause new cold sores or blisters to form. Reactivation can be triggered by any number of reasons, including:

  • stress;
  • sun exposure;
  • fever;
  • trauma to the body (injury or surgery);
  • menstruation;
  • certain medications.


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