What is a Cold Sore?

A common infection that affects 8 of 10 people.

A cold sore or fever blister — also called oral herpes — is an infection on or around the lips or mouth area caused by the herpes simplex virus type 1 (HSV-1). The cold sore virus is very common, and most people get it by the time they are 20 years old.

The cold sore virus lives in your nerve tissue. While “asleep,” the virus produces no symptoms. When it “wakes up,” the virus can affect your skin’s surface and cause a blister to form on the lip area or other areas.

The virus that causes cold sores and future outbreaks is contagious and spreads easily. Once you get the virus, you’ll always have it, even though you may not always have visible sores. Cold sore blisters or sores usually appear when your defenses are down — when you are stressed, or your immune system is weak. Common cold sore triggers include exposure to sun, stress, sickness, having surgery and having your period.

There is no cure for fever blisters or the cold sore virus, but there are ways to manage your cold sore symptoms.

Make sure to talk to your doctor if:

  • Cold sore symptoms do not improve in 7 days
  • Irritation, pain or redness persists or worsens
  • Swelling, rash or fever develops