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Canker Sore or Cold Sore? Here’s the Difference

Is it a canker sore or a cold sore? Symptoms can be similar.

At one time or another, many of us have experienced a painful canker sore or cold sore. Sometimes, the appearance and symptoms of each are similar, making it difficult to know how to treat the symptoms most effectively. If you develop a sore in or on your mouth, here’s how to tell what’s happening.

What do canker sores and cold sores look like?

Canker sores are small round ulcers that appear inside your mouth—usually on the inside of your cheek or near your gums. They can appear alone or in clusters.

Cold sores are small blisters that can appear on your gums, lips, tongue, and or the roof of your mouth. They usually appear in clusters.

What causes each kind of sore, and how long do they last?

While canker sores are not contagious, they may last up to two weeks. Their root cause is unknown.

However, cold sores result from a herpes simplex virus (usually—but not always—Type 1, which is not sexually transmitted). The virus enters the body via contact with saliva. Once the virus enters your body, it remains there. It may remain dormant for long periods of time until it is triggered into an active state and a cold sore develops. Active cold sores are contagious, so it’s important to avoid kissing and other intimate physical contact, and to avoid sharing cups, eating utensils, towels, and razors. Cold sores generally last between 7 and 10 days.

What triggers a canker sore?

Any of these conditions could trigger canker sores:

  • food allergies
  • hormonal changes
  • hot, spicy foods
  • infections
  • stress
  • vitamin deficiencies

What triggers a cold sore?

Only two of the triggers for cold sores are similar to those of canker sores:

  • colds, fever, or flu
  • exhaustion
  • hormonal changes
  • stress
  • excessive sun exposure
  • facial cuts or trauma

What can I do for the discomfort of canker sores and cold sores?

If you have a canker sore, it’s important to avoid acid-producing foods and drinks, which will aggravate the discomfort. You may get relief from applying ice or over-the-counter lip balms or ointments. Your pharmacy will also have mouth rinses that can help. Dr. Gio recommends taking an amino acid called lysine, which is available over the counter; beginning lysine as soon as a sore may help minimize its duration.

If the discomfort is severe, you may want to try a pain reliever such as ibuprofen or acetaminophen—but always check with your doctor for the best recommendation. At Winchester Dental, we also offer cold laser therapy to help relieve the effects of severe canker sores.

For cold sores, you can use ice to relieve the discomfort, and visit the pharmacy for specially formulated lip balms, ointments, and sunscreen. Regularly using sunscreen on your face (around your mouth) can also help you avoid new outbreaks if you’ve had cold sores in the past.

To help boost your immune system’s fight against cold sores, you can eat more cruciferous vegetables such as broccoli, kale, and cauliflower. You’ll want to avoid foods with arginine, a cold sore-triggering amino acid in nuts, chocolate, and oats. And as much as you can, work on minimizing your stress. Give yourself time for the restorative, calming activities that help you relax.

Do I need prescription medication?

As uncomfortable as a canker sore may be, you won’t need prescription medication to treat it. You generally won’t need a prescription for cold sores either, unless you have a severe or frequently recurring case and your doctor recommends antiviral therapy. If you’re unsure, it’s best to ask.


Cold Sores. Harvard Health Publishing. https://www.health.harvard.edu/oral-health/cold-sores. Published April 2015. Accessed November 11, 2019.

Cold Sores vs. Canker Sores: What Are They and How Do I Get Rid of ‘Em? Penn Medicine. https://www.pennmedicine.org/updates/blogs/health-and-wellness/2019/july/cold-sores-and-canker-sores. Accessed November 11, 2019.

What Are Cold Sores? WebMD. https://www.pennmedicine.org/updates/blogs/health-and-wellness/2019/july/cold-sores-and-canker-sores. Accessed November 11, 2019.