Conditions · FAQ
What are cold sores, and what causes them?
Short answer
Cold sores are small, painful blisters on or around the lips caused by the herpes simplex virus, most often HSV-1. After the first infection, the virus stays in nerve cells and can become active again. Stress, illness, and sun exposure can trigger outbreaks, though triggers differ from person to person.
Cold sores are caused by the herpes simplex virus, most often type 1, also called HSV-1. They often appear along the edge of the lips, but they can also affect nearby skin. The virus spreads through contact with infected skin or saliva. Many people get the virus during childhood, sometimes without knowing it.
After an infection, the virus stays in nerve cells. It may remain quiet for long periods and then become active again. Stress, fever, other illnesses, and sun exposure can trigger an outbreak. Some outbreaks happen without a clear trigger. Having cold sores does not mean you have poor hygiene.
A licensed physician in your state can review your symptoms and decide whether treatment is appropriate. Antiviral medicine may shorten an outbreak, but it does not remove the virus from the body. Results vary. If a sore looks unusual, does not heal, or is near your eye, seek medical care rather than assuming it is a routine cold sore.
Sources
Written by the Verra clinical team · Medical review pending
General information, not medical advice. If you're in crisis, call or text 988.