Herpes Home > Cold Sore Triggers

While symptoms are not usually present with an initial infection, certain factors may trigger later outbreaks of a cold sore. These can include exposure to sunlight or other UV light, the common cold or flu, hormonal changes, and emotional stress. By being aware of your cold sore triggers and avoiding them as much as possible, you can help prevent outbreaks from occurring.

What Triggers a Cold Sore?

A cold sore (known medically as herpes labialis) is a type of skin condition caused by the herpes simplex virus. It is transmitted through direct skin-to-skin or mucous membrane contact.
Most people infected with this virus do not show symptoms when transmission first occurs. However, like other herpes viruses (such as the virus that causes chickenpox and shingles), the herpes simplex virus stays in the body after the initial infection. Occasionally, the virus can become active again, and another cold sore may form.

Specific Cold Sore Triggers

Herpes research scientists have identified several factors that appear to cause an outbreak of herpes. These cold sore triggers include such things as:
  • Fever
  • An illness such as the common cold or flu
  • Emotional stress
  • Injury to the skin around the lips, including cracked lips
  • Trauma that may occur with dental work, cosmetic surgery, or chemical peels
  • Exposure to sunlight or other UV light, such as in tanning beds
  • Exposure to cold weather or wind
  • Hormonal changes, such as those seen during menstruation or pregnancy
  • Fatigue.
Despite knowing these triggers, not every cold sore is a result of one of these factors. In fact, in a lot of cases, it is not exactly known why a particular person develops a cold sore.
Scientists are also still trying to understand exactly how the factors that can trigger cold sores interact with the immune system and the virus to prompt a recurrent outbreak.
Written by/reviewed by:
Last reviewed by: Arthur Schoenstadt, MD
Last updated/reviewed:
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