What Causes a Cold Sore?

A cold sore is a painful sore that often forms on the lips or around the mouth. 

While a cold sore is caused by the herpes virus, many factors can act as triggers.

The American Academy of Dermatology says potential triggers include:

• Feeling run down, stressed or tired.
• Having the flu, a fever or a cold.
• Being exposed to the sun.
• Having hormonal changes as a result of pregnancy or menstruation.
• Having an injury or trauma to the face from a cut, dental work, shaving or surgery.