Are Cold Sores Contagious? Yes, Here’s What You Should Know (With Pictures)

Many people develop cold sores from time to time. These small, painful blisters — also known as fever blisters — can form on the lips, around the mouth, and on the tongue. The herpes simplex virus (HSV) causes these blisters. 

HSV is very contagious and can easily spread from person to person. That’s why so many people experience cold sores. Here’s what to know about how long cold sores are contagious.

How long are cold sores contagious?

Cold sores themselves aren’t contagious. But HSV, the virus that causes cold sores, is contagious. 

People shed HSV for about 1 to 3 weeks when they have a cold sore. HSV lives inside cold sores. So you can pass the virus to others from the time a cold sore appears until it completely heals. 

Some people get an itchy, burning, or painful feeling on their skin before a cold sore appears. These symptoms can start 1 or 2 days before the cold sore develops. During this time, it’s possible to pass HSV to other people when you feel these symptoms — even if you haven’t developed a cold sore yet. 

A cold sore can take between 1 and 3 weeks to completely heal. Scabbed-over cold sores can still contain HSV. So it’s a good idea to take precautions until your skin fully heals. 

Symptoms of a cold sore

Most people with cold sores experience symptoms over the area where they have a cold sore. This can include lip or mouth:

• Pain

• Redness

• Swelling

• Itching

• Burning

You may experience more severe symptoms the first time you develop cold sores, like:

• Fever

• Many blisters inside the mouth or on lips

• Painful, swollen gums

• Sore throat

• Headache

• Muscle aches

• Swollen lymph nodes

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This is called a primary HSV infection, and it’s more common in children. It happens because the immune system is still learning how to respond to HSV. 

When are cold sores most contagious? 

You’re most contagious during the first 48 to 96 hours after the blisters appear. After that, the amount of virus inside the cold sore goes down. That means it’s harder for HSV to pass to other people. 

What are the stages of a cold sore?

Cold stores go through several stages as they develop and heal:

• Prodrome: This stage describes the days before the blister appears. People may feel burning, soreness, or tingling on their skin where the cold sore will develop. This lasts 1 to 2 days. Not everyone experiences this stage.

• Blister: The cold sore blister appears on the skin. You may develop only one large blister or a cluster of smaller blisters. Blisters grow, become red, and fluid-filled. This stage lasts 1 to 2 days. 

• Weeping: The blister or blisters break open and ooze liquid. This liquid contains HSV. It’s important to take steps to avoid spreading the virus to others during this stage. Luckily, this stage lasts only 1 day. 

• Crusting: Your body will start to heal and form a scab over the next 2 to 3 days. This can look like crusting over your blister. Don’t pick at this scab, which can increase the risk of a bacterial skin infection. 

• Healing: Your scab will fall off and be replaced by smaller scabs over the next 1 to 3 weeks as your body heals. 

Images of cold sore stages

A cold sore’s appearance will change as they go through these stages. Here’s what the different stages can look like.

A cold sore is in the blister stage.

A cold sore breaks open.

How do cold sores spread?

Cold sores spread when a person who doesn’t have HSV comes into contact with the virus. Since HSV lives inside cold sores, it can spread by direct contact with a cold sore. Cold sores can also spread when a person comes into contact with an object that has been contaminated with HSV. 

Some ways HSV spreads include:

• Kissing or intimate contact 

• Sharing utensils, straws, and cups

• Sharing items that touch lips like lip balm, lipstick, or razors

If you have a cold sore or think you might be getting one, avoid kissing or sharing items that touch your mouth. 

How do you treat contagious cold sores?

Unfortunately, there’s no cure for cold sores. In other words, HSV can’t be completely eliminated from the body. But there are things you can do to treat cold sores and make them less likely to come back. These things will also help prevent the spread of HSV to other people.

Medication

Cold sores will heal on their own, but treatment can help them heal faster. Treatment works best if it’s started soon after a cold sore develops — ideally within 24 hours of noticing a cold sore. Cold sore medications include creams applied directly to the cold sore and prescription medications you can take by mouth.

Popular over-the-counter (OTC) creams for cold sores include:

• Docosanol (Abreva)

• Zinc oxide and zinc sulfate

• Benzocaine (Orajel)

Prescription oral medications for cold sores include:

• Acyclovir 

• Valacyclovir

• Famciclovir 

How long do cold sores last?

Untreated cold sores usually go away in about 1 to 2 weeks. But, in some people, they can last up to 3 weeks. Using a cold sore treatment can lessen symptoms and shorten a cold sore episode by 1 to 2 days. 

How can you prevent cold sores?

It’s a good idea to take steps to lower the risk of passing HSV to others. Until your cold sore heals and you’re no longer contagious, avoid sharing any items that go in, or near, your mouth. And avoid kissing and sexual activity until your cold sore heals. 

Keep in mind that you can pass HSV to other parts of your body. Try to avoid touching your eyes when you have a cold sore so you don’t spread HSV to your eyes. HSV can cause keratitis, a serious eye infection that can cause vision loss. If you need to touch your eyes to put in or remove contact lenses, always wash your hands first. It’s also a good idea to wash your hands before and after putting on cold sore creams.

To prevent cold sores from reappearing, protect your lips from the sun using a lip balm with SPF. And throw away any lip products you used while you had a cold sore. 

When to seek care for a cold sore

Cold sores usually heal on their own. Many people manage cold sores at home with the help of OTC medications and self-care. But you should seek care right away if you:

• Develop cold sores near your eyes

• Have symptoms like fever, neck stiffness, headache, or confusion

• Aren’t able to eat or drink because of cold sore pain

• Develop many blisters inside your mouth, or the sores seem like they’re spreading

• Develop skin redness, pain, or warmth around your cold sore

• Have a weakened immune system and develop a cold sore

You should also seek care if your cold sore doesn’t start to heal within a few days or isn’t following the cold sore stages. This may be a sign that your blister could be caused by something else. 

You should talk to your healthcare team if you get frequent cold sores. They can offer prescription medications that can prevent cold sores and help breakthrough cold sores heal faster. 

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Written by:

Christine Giordano, MD

Christine Giordano, MD, is board-certified in general internal medicine. She received her medical degree from Rutgers New Jersey Medical School and completed residency at Thomas Jefferson University.

Edited by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

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