When Is A Cold Sore No Longer Contagious?

The herpes virus that causes cold sores is extremely contagious, and HSV-1 infects more than 66% of the human population.¹

Normally, cold sore blisters rupture on their own, forming a scab that will ultimately peel off. Since this process often takes two weeks, cold sores can still spread after they have scabbed over. Because HSV-1 is very infectious, it's critical to understand how the virus spreads and what you should do to prevent getting it.

Maybe you’re wondering when cold sores become contagious and how long until they won’t spread anymore. Let’s find out.

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What are cold sores?

Cold sores are those unpleasant little blisters that emerge and seem to remain on your lips. The common and infectious herpes simplex virus (HSV) causes cold sores. HSV-1 is present in more than half of adult Americans. Around 30% of individuals with oral herpes will have recurring cold sore outbreaks.²

Before they burst and develop a scab, cold sores may cause soreness, a burning sensation, or itching in the affected area. These tiny blisters often appear alone or in a group on the lips or in the area surrounding the mouth. A cold sore will normally heal in seven to ten days without treatment. However, the virus is highly infectious and readily spread.

The cold sore virus can infect anyone and stays in the body for the rest of your life. It will typically be dormant, with sporadic outbreaks resulting in a cold sore.

What are the symptoms of cold sores?

Symptoms manifest differently person-to-person. These are the most prevalent symptoms:

  • Tingling lips, a prevalent symptom before cold sores emerge

  • Lips and mouth blisters that start small, grow, rupture, and crust over

  • Dryness, irritation, and itching of the lips and mouth

  • Sore lips and mouth

Some people with HSV get cold sores, which appear in response to a trigger event like a cold. Additionally, the following factors might bring on a cold sore outbreak:

  • Feverish conditions, such as influenza or chest infections

  • Sunlight

  • Wind exposure

  • Hormonal fluctuations, such as menstruation

  • Emotional or bodily strain

When is a cold sore no longer contagious?

Cold sores can be contagious for up to a week. The cold sore is infectious as soon as symptoms develop, including tingling in the area where the sore forms. Many people who get cold sores start worrying if they see something odd around their mouths.

It can be difficult to tell when they need to take measures to stop the virus from spreading to others. Common problems like chapped lips, dry skin, and other ailments can all resemble the beginning of a cold sore.

Most people detect the development of a cold sore 48 hours after the tingling sensation begins. Blisters filled with fluid form, and the region may become reactive and painful. When the blisters burst, you have a higher chance of spreading the virus to other people.

The cold sore begins to heal after 72 hours, scabbing over the blistering regions.

It's a common misconception that cold sores are no longer contagious after they have scabbed over. A cold sore is infectious until it heals fully. Without adequate medical care, this might take up to two weeks.

How can you stop cold sores from spreading?

Cold sores are transmitted by skin-to-skin contact, such as kissing, oral sex, or sharing things such as bathrobes, eating utensils, and straws. The virus enters your body through any break in your skin, which may or may not be visible to you. Here's how to keep cold sores from spreading to others.

Avoid touching the affected region

If you must scratch it, wash your hands properly afterward. Use a cotton swab to apply any topical medications rather than your finger. You should not pick at the scab, as this will only prolong the healing process.

Do not kiss or nuzzle infants

It is risky to kiss newborns when you have a cold sore because babies lack a fully functional immune system, meaning they are far more susceptible to the virus. 

Don't share any personal things

This applies to food, beverages, flatware, cups, toothbrushes, clippers, and any product you use for cold sores.

Avoid kissing and oral sex

Although a separate strain of HSV (HSV-2) usually causes genital herpes, your sexual partner can get "oral herpes" (HSV-1) on their genitalia after coming into contact with a cold sore in your mouth. Avoid kissing and oral sex until all symptoms subside and heal.

Avoid your triggers

There is less chance of illness spreading when there are fewer outbreaks. The virus usually remains dormant until something triggers it. Everyone's cold sore triggers are unique, but you can reduce flare-ups by learning about your triggers and avoiding them.

Is cold sore treatment available?

Yes, some medications can hasten the healing process. Although the HSV-1 virus that causes cold sores has no known cure, you can speed up the healing process. The best way is to take medicine as soon as you notice any symptoms, such as tingling or itchy, red skin.

Many people have symptoms that indicate the onset of a cold sore. Seek medical treatment if you have any of the following issues:

  • You have a compromised immune system, increasing your chances of complications

  • Your cold sore does not heal after two weeks

  • Your symptoms worsen or become more frequent

  • You realize that the discomfort is moving to your eyes

The lowdown

Cold sores are tiny blisters that develop on or around the lips and mouth. In most cases, the blisters rupture, forming a scab that falls off. While cold sores are extremely infectious, they are typically not dangerous. Cold sores usually resolve in healthy people in one to two weeks.

Frequently asked questions

How do you know the cold sore is gone?

The scabs will peel off after your body controls the infection. Without treatment, this usually happens 8–10 days after symptoms begin. It is normal for the skin behind the scabs to appear pink or reddish after the scabs come off.

When do cold sores become contagious?

Cold sores are contagious at all phases of growth and healing, so you can transfer HSV-1 when you have active sores. Importantly, HSV-1 can be contagious at any time, whether or not you have a cold sore. However, you will be most contagious when the blisters burst.

  1. Herpes simplex virus | World Health Organization

  2. Chapter 36 persistence in the population: Apidemiology, transmission (2007)

Other sources:

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