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. Once a person comes in contact with HSV, the virus stays inside their body, so cold sores can develop again. 

Cold sores are contagious. HSV can easily spread from person to person. That’s why so many people experience cold sores. If you get cold sores, here’s what you need to know about how long cold sores are contagious.

How long are cold sores contagious?

Cold sores are contagious for a time period ranging from 1 to 3 weeks. Cold sores are contagious from the time they appear until they completely heal. 

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 before the cold sore appears. 

Cold sores are no longer contagious once they completely heal. This can take from 1 to 3 weeks. 

Even if your cold sore is scabbed over, it can still be contagious. So it’s a good idea to take precautions until your skin fully heals. 

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• Can you get cold sores from sharing a drink? It’s possible, but you can minimize your risk. Learn more about how cold sores are transmitted.

When are cold sores most contagious? 

Cold sores are most contagious during the first 48 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. 

Images of cold sore stages

When they appear, cold sores go through different stages before healing:

1. Blisters: Bumps appear to then turn into blisters.

2. Open blisters: Blisters break open and a yellow fluid can leak out.

3. Crusting: Open blisters form crusts and scabs.

Here are some pictures of what a cold sore looks like in different stages. 

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 the HSV virus lives inside cold sores, HSV 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 by the HSV virus. Some ways cold sores spread 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, the HSV virus cannot 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 the HSV virus 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. 

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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:

Karla Robinson, MD

Karla Robinson, MD, is a medical editor for GoodRx. She is a licensed, board-certified family physician with almost 20 years of experience in health through varied clinical, administrative, and educational roles.

Reviewed by:

Maria Robinson, MD, MBA

Maria Robinson, MD, MBA, is a board-certified dermatologist and dermatopathologist who has practiced dermatology and dermatopathology for over 10 years across private practice, academic, and telehealth settings. She is a fellow of the American Academy of Dermatology and the American Society of Dermatopathology.

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Images used with permission from VisualDx (www.visualdx.com).