What are cold sores?

Audrey K. Chun, MD
Geriatric Medicine
Despite their name, cold sores aren't connected to colds -- they're just more likely to happen when your immunity is compromised by fighting an infection such as a cold. They're caused by a common virus called the herpes simplex virus. Once the initial infection has healed, it lies dormant in the nerve cells in your skin and may periodically emerge again. Fever, stress, fatigue and sun exposure can trigger a recurrence.

Cold sores -- caused by herpes virus Type 1 or Type 2 -- are contagious. The initial infection (primary herpes), which often occurs before adulthood, may be confused with a cold or the flu. The infection can cause painful lesions to erupt throughout the mouth, and some patients can be quite ill for a week. Most people who get infected with herpes do not get sick, however.

Once a person is infected with herpes, the virus stays in the body, where it may remain inactive. Unfortunately, in some people, the virus becomes activated periodically, causing the cold sore to appear on the lips or other sites. A variety of irritants (wind, sun, fever, stress) can cause a flare.

Dr. Michael Roizen, MD
Internal Medicine

Surely, there are plenty of places on your body where you love a little tingling, but right above your lip before a first date, an interview, or your reality show tryout isn't one of them. What starts as a tingle and ends as a full-blown cold sore can be as painful as it is embarrassing. They can recur when you have a cold, which is why they're called cold sores. They typically last two weeks. The leading cause of cold sores: herpes infections, which are transmitted through saliva, through kissing, or sharing other people's cups. This is called herpes type 1, not to be confused with the genital variety called herpes type 2. While you have a cold sore, kissing or giving someone oral sex can transmit the herpes virus to that person, so refrain. Don't share cups, toothbrushes, forks, or other things that touch your mouth while you have a cold sore, either.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.