Cold Sores, Explained in Just 2 Minutes

Statistically, you likely carry the virus that causes cold sores.

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Here’s a stat that might make your eyes balloon: Around half of the population carries the herpes simplex virus—the virus that causes cold sores—according to the Centers for the Disease Control and Prevention.

Alright, don’t panic. That might sound high, but many people who are infected by the virus don’t actually have symptoms on a regular basis. If you do have the herpes simplex virus type 1 (HSV-1), there’s a good chance you haven’t had symptoms since you were in elementary school. (Don’t worry: It’s not the same as genital herpes, which is dubbed HSV-2.)

HSV-1 is *extremely* contagious, and most Americans are infected by their 20th birthday. That’s why cold sores (or herpes simplex labialis) are common and totally normal among young children. Catching the virus in adulthood is pretty rare.

When HSV-1 first infects a child, they may have flu-like symptoms as the immune system reacts to the presence of the virus. The symptoms may last for a week or two, according to the American Academy of Dermatology, and they include:

  • Mouth sores, usually inside the mouth (on the tongue, gums, or throat) or on the lips

  • A burning sensation in the mouth

  • Sore throat

  • Swollen lymph nodes

  • Fever

  • Body aches and headaches

  • And nausea.

But after that, HSV-1 tends to go dormant for a while. The virus goes to your nerves and “sleeps,” and it may remain silent for months, years, or even a lifetime. Some people with HSV-1 never get cold sores, while others get them regularly.

If HSV-1 reawakens, the cold sore outbreak isn’t as dramatic as it was when you were first infected. When a cold sore appears, you’ll likely feel a burning, itchy, tingling sensation somewhere on your skin. Within a day or two, a cold sore may appear on that spot (but it’s possible to get the “warning signs” without ever getting the cold sore).

The cold sore that appears will be a painful blister (or cluster of blisters) filled with a pus-like fluid. Cold sores tend to form on the lips or around the mouth—but they can form anywhere on the face. After a few days, the cold sore will start to scab over.

If you know you’ve had cold sores and worry about spreading the virus to others, you can breathe easy: HSV-1 only spreads when there’s an active cold sore. The cold sore is contagious through direct contact until it scabs over.

If you’ve got an active cold sore, treatment includes antiviral medications to shorten the outbreak and help thwart HSV-1 from spreading to others (if they’re not already infected). While the cold sore is active, avoid sharing food, personal items, or intimate contact until HSV-1 slinks back into hibernation.