After you have been infected with HSV-1, the virus never goes away. It remains dormant (inactive) in a group of nerve cells in your face called the trigeminal ganglion.
When the virus is triggered, or activated, it “wakes up” and travels through your nerves to your lips, where a cold sore develops. After an outbreak, the virus goes back to sleep in your body.
What triggers a cold sore in one person might not cause an outbreak in another person. Some people with HSV-1 never develop a cold sore.
A cold sore can be activated by a variety of factors, including: