Cold sores are caused by the herpes simplex virus which hides in a nerve called the trigeminal nerve. During periods of stress, sunlight exposure, or other stressors the virus travels down the nerve to the skin causing the typical cold sore breakout.

It has long been a mystery not only how the virus is able to stay dormant, but also what process causes it to reactivate. Scientists at Duke University Medical Center have discovered that the virus produces a type of RNA, called LAT RNA, that blocks the production of proteins that reactivate the virus. In times of stress the virus makes a different type of RNA that causes the production of these reactivation proteins, eventually overtaking the LAT RNA, causing a cold sore.

This is an important finding since knowing how the reactivation process works enables scientists to develop therapies to block that process, stopping cold sores from developing.