Cold sores—those annoying little blisters that pop up around the lips—are far more common than most people realize. Also known as fever blisters, they’re caused by the herpes simplex virus type 1 (HSV-1), one of the most widespread viruses in the world.
According to the World Health Organization (WHO), about 67% of people under age 50 are infected with HSV-1. Many never develop visible symptoms, while others deal with recurring outbreaks that can be painful, embarrassing, and frustrating.
So, what exactly causes cold sores—and what can you do to treat and prevent them? Let’s break it down.
What Causes Cold Sores?
Cold sores are the result of an HSV-1 infection, which is usually spread through direct oral contact like kissing or sharing utensils. Once the virus enters the body, it doesn’t go away. Instead, it hides inside nerve cells and can “wake up” again when triggered by certain factors, including:
- Stress
- Fatigue
- Illness or fever
- Hormonal changes
- Extended sun exposure
- Dental procedures
When reactivated, the virus travels along the nerves to the skin, forming the well-known blisters. Although they usually appear around the lips, they can also show up on the chin, cheeks, nostrils, or even inside the mouth.
