Cold Sore vs. Canker Sore: Understanding the Difference
Dental & Oral HealthCold Sores

Cold Sore vs. Canker Sore: Understanding the Difference

Cold Sore vs. Canker Sore: Understanding the Difference
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Updated on March 10, 2024
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Distinguishing a cold sore from a canker sore isn’t always easy. Both types of sores affect the mouth area, and they sometimes mimic each other in appearance. But a cold sore isn’t the same as a canker sore. These sores differ with regard to causes, locations, symptoms, and transmission.

Can’t tell them apart? Here are a few tips to help you make the distinction.

Illustrative graphic titled How to Identify Mouth Sores shows cold sores: small blisters on lips, cheek or nose, caused by HSV and contagious. Canker Sore: flat ulcer inside the mouth, many different triggers and not contagious. Everyday Health logo
Differences in appearance and location can help you tell whether you have a cold sore or a canker sore.Everyday Health

How the Symptoms and Appearance Differ Between Cold Sores and Canker Sores

Canker sores, also known as aphthous ulcers, are mouth ulcers that look like a shallow disc and are often oval or round. These lesions can be whitish, grayish, or yellowish, and they are usually less than 1 millimeter in diameter.

A canker sore can develop as a single sore, or you may have clusters of tiny sores. These sores can be painful, making it difficult to eat, talk, and brush your teeth. But the pain usually improves after a couple of days.

A cold sore, also known as a fever blister, starts as a tiny fluid-filled blister or a cluster of them. You may notice itching or tingling one to two days before the blisters appear. These sores can cause skin redness and pain, and they eventually rupture and ooze before a scab forms.

During a first cold sore outbreak, additional symptoms may include a fever, swollen glands, sore throat, headache, and muscle aches.


Location Matters When Figuring Out if It’s a Cold Sore or a Canker Sore

The location of these lesions is another way to determine a cold sore from a canker sore. Canker sores develop on the mucous membranes inside the mouth. Therefore, you’re more likely to find these sores on the inside of the cheeks and lips, gums, soft palate, or tongue.


Cold sores, on the other hand, don’t usually appear inside the mouth, although this is possible when you are first exposed to the virus that causes them.

 Instead, cold sores often develop on or around the lips.
They can also form on other parts of the body, such as the cheeks and around the nose. The virus sometimes infects people’s eyes.


The Cause of a Cold Sore Isn’t the Same as the Cause of a Canker Sore

Cold sores are most commonly caused by the herpes simplex virus type 1 (HSV-1). This is a common virus — more than 50 percent of Americans ages 14 to 49 carry it.

 Many people get the virus as a child after being kissed by someone who is infected.

Some infected people never develop a cold sore because the virus can lie dormant in the body for years.

Certain factors can reawaken the virus and spark a cold sore:


  • Exposure to strong sunlight
  • Stress
  • Tiredness
  • A fever or infections
  • Hormonal changes
  • Facial procedures or laser treatment
HSV-1 and HSV type 2 (HSV-2) are viruses that can cause cold sores, as well as genital herpes. You can get HSV-2 cold sores if you engage in oral sex with someone who has genital herpes, but this isn’t the only way to spread these types of cold sores. A person with HSV-2 cold sores can infect another person through kissing, too.

 Likewise, HSV-2 can also be transmitted from a mother’s genital tract to her newborn infant, says Allison Arthur, MD, a board-certified dermatologist at the Sand Lake Dermatology Center in Orlando, Florida.
Canker sores, on the other hand, aren’t caused by the herpes virus. The exact cause of canker sores is unknown. But it’s believed that certain factors can increase your risk. Some people get a canker sore after eating citrus fruits or acidic foods, whereas others develop sores because of a nutritional deficiency (in, for example, vitamin B12, folic acid, or iron).

 Certain medications, such as nonsteroidal anti-inflammatory drugs like ibuprofen, can also cause canker sores.
Other factors that can trigger a canker sore include smoking, stress, and an injury inside the mouth.

 Some autoimmune diseases and a weakened immune system are associated with canker sores as well.


How Cold Sores Are Spread Is Different From Canker Sore Transmission

Another difference is how these lesions spread. Cold sores are contagious. Not only do they spread from person to person through kissing, but also through sharing eating utensils, drinks, and personal items.


It’s important that you don’t kiss or share food or drinks with someone who has an active cold sore. You should also wash your hands after touching a cold sore. This prevents spreading a cold sore to others, as well as spreading the virus to other parts of your body.

Cold sores are most contagious when blisters rupture. But you can still pass the virus to others until the sore is completely healed.

A canker sore, on the other hand, isn’t contagious and doesn’t spread from person to person.


A Final Word on How Cold Sores Are Different From Canker Sores

Even though these sores differ, they do share some similarities. It usually takes between one and three weeks for cold sores and canker sores to heal, and they often go away on their own without treatment.


Some people also deal with recurrent cold sores and canker sores. For a recurrent cold sore, ask your doctor about suppression therapy with a daily antiviral to reduce the frequency of outbreaks. You should also see a doctor for repeated canker sores. This can be a sign of an autoimmune disease or a vitamin deficiency.

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Natalia Johnsen, MD

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Member of American College of Lifestyle Medicine

Natalia Johnsen, MD, is a triple board-certified physician in internal medicine, lifestyle medicine, and obesity medicine, practicing as an internist and consultant at the Vancouver Clinic in Vancouver, Washington.

Dr. Johnsen began her medical career as an ob-gyn in Russia before relocating to the United States in 2000. She completed her internal medicine internship at the University of Nevada and her residency at a Stanford-affiliated program in Santa Clara, California.

Deeply interested in the impact of lifestyle on both physical and mental health, Johnsen transitioned her focus toward prevention-based care after witnessing how many chronic conditions could be avoided or improved through lifestyle interventions. She became board-certified in lifestyle medicine in 2021 and further expanded her expertise by earning board certification in obesity medicine in 2025.

Johnsen is passionate about empowering patients with evidence-based tools to achieve sustainable health and long-term well-being.

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Valencia Higuera

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Valencia Higuera is a writer and digital creator from Chesapeake, Virginia. As a personal finance and health junkie, she enjoys all things related to budgeting, saving money, fitness, and healthy living. In addition to Everyday Health, Higuera has written for various publications, including Healthline, GOBankingRates, MyBankTracker, and The Mortgage Reports.
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Resources
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  3. Cold Sore: Symptoms and Causes. Mayo Clinic. January 5, 2024.
  4. Cold Sores: Overview. American Academy of Dermatology.
  5. Cold Sores: Who Gets and Causes. American Academy of Dermatology.
  6. Cold Sores (HSV-1). KidsHealth. February 2019.
  7. Cold Sore. NHS Inform. December 5, 2023.