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    Mayo Clinic Minute: 3 things you didn’t know about cold sores

Cold sores on the lips can be embarrassing and tough to hide, but they're more common than you might think. They're so common, that Dr. Pritish Tosh, a Mayo Clinic infectious diseases specialist, says you might not have a reason to be embarrassed when you have a cold sore.

Watch: The Mayo Clinic Minute

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"About 70-plus percent of the U.S. population has been infected with herpes simplex 1," Dr. Tosh says. "Now, a very small percentage of those people will actually develop cold sores."

Dr. Tosh says genetics determines whether a person will develop cold sores or not.

"A proportion of the population, they don't quite have the right immunologic genes and things like that," he says. "And, so, they're not able to handle the virus as well as other people in the population."

The problem is people can spread the herpes virus whether they develop cold sores or not.

Herpes virus spreads through physical contact, like kissing, sharing a toothbrush – even sharing a drinking glass – or through sexual contact.

"Since the number of people who are infected but don't have symptoms vastly outnumber the people who are infected and have symptoms, most new transmissions occur from people who have no idea that they are infected," Dr. Tosh says.

That's why he says it's time to rethink how cold sores are viewed and start looking at them as a genetic problem ─ not a problem of promiscuity.