Cold sores—sometimes called fever blisters—are a common skin issue caused by the herpes simplex virus type 1 (HSV-1). Though usually not dangerous, they’re contagious, often painful, and tend to come back once you’ve had them. That’s because the virus stays in your body for life, hiding in nerve cells and reactivating when triggered.
What Brings on Cold Sores?
The main cause is HSV-1, often picked up in childhood through close contact like kissing or sharing items. After the first infection, the virus settles in your body and can remain inactive for long periods.
HSV-1 differs from HSV-2, which is more commonly linked to genital outbreaks—but either virus can affect different areas based on how they’re passed from person to person.
