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Updated on May 19, 2023
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Cold Sores

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What are Cold Sores?

Cold sores are sometimes called fever blisters. The small blisters cluster on and around your lips. They are caused by a contagious virus called herpes simplex virus (HSV).3

There are just two types of HSV: type 1 and type 2:3

  1. Type 1 HSV is oral herpes, or cold sores
  2. Type 2 HSV is genital herpes

About 600,000 people in the United States develop an infection with type 1 herpes.2 It infects more than half of the population by the time they reach their 20s.5

About 90 percent of the United States population is also exposed to HSV-1 by the time they are 70 years old.2

In other words: Cold sores are common. But they can still be uncomfortable and painful.

What Do Cold Sores Look Like?

Cold sores can be embarrassing since they develop on the face. They occur in stages:

  1. Initial symptoms — You may feel some tingling, itching, tightness, or burning on the lips. You may also have other symptoms like a fever or feeling run down. This all happens in the first day or two.
  2. Progression — You will notice the blister start to form on or around your lips. This occurs around the second day of cold sore formation.
  3. Rupture — The blister will pop. It may ooze and/or bleed at this point. This stage can be very painful. This is the stage that is most contagious.
  4. Scabbing — After the blister breaks open, it will start to crust over. A scab will form over the next few days. This usually occurs around day five to eight.
  5. Resolution — The skin will heal with time, and the scab will clear up. This is the final stage of a cold sore, once it has completely gone away. A cold sore typically takes about two to three weeks to clear up completely.

Medical Images of Cold Sores

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Cold sores look like small blisters that are filled with fluid. They appear on and/or around your lips. They are usually clustered together.3

After the blisters pop, a scab will form. This scab can last a few days. Therefore, cold sores usually take about two to three weeks to heal.3

What Causes Cold Sores?

Cold sores are the product of the herpes simplex virus type 1. The herpes simplex virus is twofold. Type 1 affects the mouth area, while type 2 affects only the genitals.

Cold sore outbreaks can recur. Recurrences can be triggered by a number of factors. These include:3

  • Other viral infections
  • Fevers
  • Hormonal changes or imbalances
  • Dietary changes
  • Stress
  • Fatigue
  • Exposure to sunlight
  • Exposure to wind
  • Immune system changes
  • Skin injuries

There are also a few factors that may increase your risk of developing cold sores:3

  • Atopic dermatitis (eczema)
  • Chemotherapy for cancer
  • Anti-rejection drugs for organ transplants

Cold sores do not discriminate. Anyone can contract them at any stage in life. 

Signs & Symptoms of a Cold Sore 

Some common signs and symptoms of a cold sore include:3

  • Tingling or itching on and/or around the lips
  • Pain or discomfort on and/or around the lips
  • Blisters forming on and/or around the lips
  • Oozing or crusting on and/or around the lips
  • Scabs forming on and/or around the lips
  • Fever
  • Headache
  • Muscle aches
  • Swollen lymph nodes
  • Sore throat
  • Painful gums

While not all the symptoms of cold sores are dangerous, they can be uncomfortable and affect confidence.

Canker Sores vs. Cold Sores: What’s the Difference?

Cold sores are different from canker sores, which are also common. 

Canker sores, sometimes known as aphthous ulcers, are small and shallow lesions. They develop on the soft tissues in your mouth.1

Canker sores typically develop on the inside of the lips or at the base of the gums. They do not surface on the lips, unlike cold sores.1

Cold sores and canker sores also look different. Canker sores are round or oval and have a white or yellowish center with a red border.1 Cold sores are small blisters that often appear in clusters.

Canker sores can develop for a variety of reasons:1, 6

  • Minor mouth injuries (from dental work, brushing the teeth, accidentally biting the cheek, etc.)
  • Some irritable toothpastes or mouth rinses with sodium lauryl sulfate (SLS)
  • Food sensitivities
  • Allergic reactions in the mouth
  • A diet that lacks vitamin B-12, zinc, iron, or folate (folic acid) 
  • Emotional stress
  • Hormonal changes (particularly during menstruation)
  • The helicobacter pylori bacteria, which also causes peptic ulcers

Similar to cold sores, there are some risk factors for developing canker sores:1

  • Celiac disease
  • Inflammatory bowel diseases like Crohn's disease and ulcerative colitis
  • Behcet's disease, which induces inflammation in the body, including the mouth
  • A weakened immune system, which may attack healthy cells in your mouth

Canker sores can be painful, just like cold sores. They can make eating, drinking, and talking difficult. Certain foods and beverages also cause them to sting.1

The symptoms of canker sores are similar to those of cold sores:

  • Tingling or burning in the mouth
  • Pain or discomfort in the mouth
  • A white or yellow oval or circle lesion in the mouth

Unlike cold sores, canker sores do not burst, ooze, crust over, or scab.1

Most canker sores go away on their own. While some may last longer than others, canker sores tend to go away within a few days to a week or two. If your canker sore lasts longer, call your doctor to make sure it’s actually a canker sore.1

Major canker sores can take up to six weeks to heal. They can also leave serious scarring.1

Unusually large canker sores, canker sores that are extremely painful, and canker sores that do not heal within two weeks may be a sign of another health issue.1 More serious health conditions like STIs or even leukoplakia or oral cancer lesions can look like canker sores.

Canker sores are not contagious. To prevent them, you should maintain a healthy diet, keep up with oral hygiene, and minimize stress.6

Are Cold Sores Contagious? 

Yes, cold sores are very contagious. Cold sores are contagious even if you cannot physically see the sores.2

In fact, about 80 percent of HSV-1 cold sore infections have little to no signs or symptoms.2

Cold sores can spread from person to person via close contact. For example, kissing and sharing drinks can spread them.2

You can also spread type 2 herpes simplex, genital herpes, through oral sex.2

When to See a Doctor

Visit your doctor if you get cold sores frequently or have intense outbreaks. You should also reach out to your doctor if your cold sores don't heal within two weeks.

Unfortunately, there are no cures for cold sores. However, your doctor can prescribe medications and recommend home remedies to reduce discomfort.

Treatment Options for Cold Sores

While you cannot cure the herpes simplex virus type 1 (or type 2), you can make outbreaks more manageable. Some treatment options for cold sores include:3, 4

  • Prescription antiviral pills
  • Prescription antiviral creams
  • Over-the-counter pain medications to manage the symptoms
  • Fever reducers
  • Pain relievers for headaches and muscle pain

How to Prevent & Manage Cold Sores 

To prevent cold sores, don’t come into close contact with anyone who exhibits symptoms. Also, don’t kiss or share drinks with someone who shows signs of a cold sore. 3

You should avoid sharing all items that touch your mouth.3

  • Chapstick
  • Lipstick
  • Lip gloss
  • Other makeups
  • Cups
  • Dishes
  • Forks, spoons, and other utensils
  • Towels
  • Wipes

Don’t engage in unprotected oral sex with someone who shows signs of the herpes simplex virus. While you can't always see the signs, you can always use protection.

You should also do your best to stay healthy. A weakened immune system will be more susceptible to viral infections like the cold sore virus.3

The above medications, like cold sore creams, can help you treat cold sores to better manage outbreaks.

What is the Outlook for Cold Sores?

Cold sores are incurable. And over half the population lives with them.

However, cold sores are a common and easily manageable viral infection. Talk to your doctor about treatment options.

Last updated on May 19, 2023
6 Sources Cited
Last updated on May 19, 2023
All NewMouth content is medically reviewed and fact-checked by a licensed dentist or orthodontist to ensure the information is factual, current, and relevant.

We have strict sourcing guidelines and only cite from current scientific research, such as scholarly articles, dentistry textbooks, government agencies, and medical journals. This also includes information provided by the American Dental Association (ADA), the American Association of Orthodontics (AAO), and the American Academy of Pediatrics (AAP).
  1. Canker Sore.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 3 Apr. 2018.
  2. Charles Patrick Davis, MD. “Are Cold Sores (Fever Blisters, HSV) Contagious? Treatment.” RxList, RxList, 12 Jan. 2021.
  3. Cold Sore.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 17 June 2020.
  4. Cold sores.” Cedars.
  5. Cold Sores.” MedlinePlus, U.S. National Library of Medicine, 29 Sept. 2020.
  6. Everything You Ever Wanted to Know about Canker Sores.” Cedars.
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