Can I Spread a Cold Sore by Kissing?

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  • Written By: Gregory Hanson
  • Edited By: Susan Barwick
  • Last Modified Date: 14 November 2019
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It is very easy to spread a cold sore by kissing. Cold sores are caused by the herpes simplex virus, and a person who has been infected by this virus can spread it to an uninfected person by kissing even when the cold sore is not particularly active. It is also possible to spread a cold sore by kissing when the cold sore has already healed over and disappeared, although this is less likely to occur.

The virus that causes cold sores can infect any part of the human body, but spreads most easily to the areas around the mouth and genitals. Two different types of the herpes simplex virus exist. HSV–1 is more likely to infect the mouth and cause cold sores, while HSV–2 typically infects the genitals, but can also infect the mouth and produce cold sores. The virus can survive outside of the body for short periods of time but is most often transmitted by direct physical contact. Prolonged contact increases the risk of infection.


The herpes virus establishes itself in the nerves that lead away from the surface of the skin. In many cases, the immune system can suppress the virus, and symptoms never occur. Other people infected with the virus will suffer from periodic viral outbreaks, which take the form of cold sores on the mouth and lips. These sores and the tingling that precedes their appearance indicate a high level of viral activity. This elevated level of viral activity means that it is much easier to spread the virus because there are many more viruses on the surface of the skin.

The probability that a person will actually spread a cold sore by kissing is determined by several factors. If the other person involved in the kiss has already been infected with the virus, even in a dormant form, he or she will have antibodies that limit but do not eliminate the chances of spreading the virus to another site of infection. A person with a weakened immune system, on the other hand, is much more likely to be infected. Careful hygiene may reduce the chances of spreading cold sores.

Medication can reduce the risk that someone will spread a cold sore by kissing. Antiviral drugs, primarily acyclovir and penciclovir, are used to treat herpes infections. They reduce the number of viral outbreaks and reduce the severity of outbreaks. By so doing, they make it less likely that a person will spread a cold sore by kissing, but do not eliminate the risk entirely.



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Post 3

@ZipLine-- You might want to check with your doctor about this. Some doctors say it's not contagious because the virus is not active, other doctors say that it is contagious but not very.

Cold sores have stages. It's active at some times when the immune system is weaker and it lies dormant at other times. As far as I know, the virus is periodically eliminated from the body through shedding even when the virus is not active. So even though the likelihood is low, there is a possibility that the virus can be spread by kissing when there is no cold sore. But it's very contagious when there is a cold sore.

If you take anti-viral medications regularly, you probably won't pass it when the virus is not active (no cold sore). But if you don't take medications, there is no guarantee.

Post 2

Does anyone know if cold sores are contagious when there is no blister? Is it okay to kiss when there is no breakout?

Post 1
Kissing is probably the easiest way to spread herpes simplex type one.

Forget kissing, HSV-1 can also be spread by sharing beauty items, drinking glasses and utensils. I have HSV-1, I think I got it from my mom. My mom and I always share our lipsticks. I knew she gets cold sores but I didn't know that cold sores are caused by a herpes simplex virus. Now, I have it.

I've told my boyfriend about it and he's knows that he may get it from me. He said he doesn't care but I do worry about it. I don't go near him when I have a cold sore blister.

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