Are Canker Sores Herpes?

By Robynn Lowe
Medically reviewed checkmarkMedically reviewed
June 29, 2022

Sores in or around the mouth can be uncomfortable—and concerning if you aren’t sure what’s causing them.

While some mouth sores are caused by sexually transmitted infections like herpes, other sores can be triggered by stress, food sensitivities, or an underlying health issue like a vitamin deficiency.

Many times, mouth sores don’t need medical attention, but you may want to use over-the-counter medication or home remedies to help ease the pain.

In order to pick the right treatment, though, you need to know what type of sore you’re dealing with.

In this article, I’ll explain what canker sores and herpes are, as well as how to identify each.

Then I’ll discuss the differences in treatment and prevention for each and when to see a doctor about mouth sores.

What Are Canker Sores?

Canker sores are small, round sores that appear in the mouth.

They typically form on the inside of the cheek, under the tongue, on the underside of the lip, or at the back of the throat.

Canker sores have a reddish appearance around the edge and a gray or white center.

They can be very painful.

They are not contagious and, unlike cold sores, are not caused by a virus. 

It’s unclear what causes canker sores.

However, certain things are likely to trigger these sores:

  • Periods of high stress
  • Food allergies or sensitivities
  • Vitamin B12, zinc, folic acid, or iron deficiencies
  • Hormone changes, such as during a menstrual cycle
  • Irritation from dental work
  • A suppressed or weakened immune system
  • Certain conditions, including HIV, AIDS, Celiac disease, or Crohn’s disease

Most sores heal on their own in 1-2 weeks. 

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What Are Herpes?

Herpes blisters are also known as cold sores or fever blisters.

They are most commonly caused by HSV-1, a virus that affects 3.7 billion people around the world.

Oral herpes outbreaks can also be caused by HSV-2, the virus associated with genital herpes.

Cold sores and HSV-1 are not always sexually transmitted infections.

The virus that causes cold sores can be passed without symptoms, either from contact with sores or from the saliva of an infected person.

Many people who have HSV-1 contract it during childhood and do not have specific viral outbreaks.

When cold sores form, tingling or other sensations may happen in the spot 1-3 days before the sore appears.

After that, cold sores take 1-2 weeks to resolve on their own and go through phases where they fill with fluid, burst, crust over, and then scab before healing.

They are most contagious when the sores burst open, since the fluid inside contains the herpes simplex virus.

Cold sores most often form on the lip line or on hard surfaces inside the mouth.

They are painful, small, reddish, and soft.

Other symptoms that may come with an oral herpes outbreak include:

How to Identify Herpes vs. Canker Sores

While oral herpes and canker sores both affect the mouth, where the sore is located can help you tell the difference between them.

  • Canker sores: Only inside the mouth on soft tissue such as the cheeks, back of throat, and underside of lip
  • Cold sores: Most commonly around the lip line, or if inside the mouth, only on harder tissue

Canker sores and cold sores also look distinctly different.

  • Canker sores: Red edge with a gray or white center. Canker sores can vary in size and in some cases, can feel quite large.
  • Cold sores: Red sore that fills with clear fluid, breaks open, crusts over, and then scabs. Cold sores tend to be smaller.

Canker sores are not caused by a virus, but they can appear if you have a virus or infection or have recently been sick.

Cold sores are caused by a virus and an initial infection can come with symptoms such as fever, swollen lymph nodes, and fatigue.

How to Treat Canker Sores and Herpes

While canker sores and herpes blisters are both mouth sores that can be extremely painful, treatment differs because each has different causes.

Canker sores

No at-home treatment will get rid of a canker sore instantly.

But the following home remedies may decrease pain and speed healing:

  • Rinse or gargle with salt water
  • Rinse or gargle with baking soda in warm water
  • Avoid spicy or acidic foods

You can also purchase over-the-counter creams and gels to help reduce pain and promote healing.

These OTC products often contain benzocaine, fluocinonide, or hydrogen peroxide.

If you have canker sores that don’t seem to resolve, see your dentist or medical provider.

You may need a steroid or antibiotic treatment for complicated canker sores, especially if you have other health conditions that make it harder for your body to heal.

Cold sores

Oral herpes blisters typically clear up on their own within 1-2 weeks.

Some OTC treatments or home remedies may help ease discomfort or slightly speed up healing time.

  • Topical antiviral creams: These can help shorten the duration of a cold sore outbreak by around one day. You can get docosanol 10% (Abreva), benzyl alcohol (Zilactin-L), and dimethicone with sunscreen (Herpecin-L) over the counter. Penciclovir cream (Denavir) or acyclovir cream (Zovirax) require a prescription.
  • Topical home remedies: There isn’t a lot of research behind home remedies, but applying coconut oil or aloe vera to cold sores may be helpful and are not likely to cause harm. They can keep the area moisturized while also soothing cracked, sore skin.
  • Pain relief: Apply an ice pack to the sore for some numbing pain relief, or consider OTC pain relievers like ibuprofen or acetaminophen.

If you experience frequent outbreaks of cold sores, your healthcare provider can prescribe oral antiviral medication to help decrease the frequency.


Herpes simplex virus, which causes oral herpes, is widespread and common.

People can contract the virus and have no symptoms.

It is not always possible to prevent the transmission of HSV-1.

However, you can minimize risks associated with sexual contact and decrease contracting herpes simplex otherwise with basic hygiene practices.

These include:

  • Avoid direct contact with herpes blisters.
  • Avoid kissing or sharing saliva with someone who has active herpes blisters. 
  • Avoid sexual activity with anyone during active oral or genital herpes outbreaks.
  • Always use condoms or dental dams when engaging in sexual contact of any kind.
  • Do not share food or utensils.

You cannot always prevent canker sores either.

But you may be able to reduce the risk of developing them by avoiding irritants such as:

  • Acidic, hot, or spicy foods
  • Chewing gum
  • Dental products that contain sodium lauryl sulfate
  • Hard toothbrushes (use one with soft or ultra-soft bristles)

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When to See a Medical Provider

If you develop painful sores in or around your mouth and you know they are canker sores or herpes blisters, you do not need to call your doctor.

However, if you develop new sores that you have never had before, or you develop abnormally large canker sores, see your healthcare provider or doctor.

They can examine your mouth to make sure there is not something else contributing to the condition.

How K Health Can Help

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Frequently Asked Questions

Are canker sores from an STD?
No, canker sores are not caused by sexually transmitted diseases. It’s unclear what causes canker sores, however, they may be triggered by stress, food sensitivities, hormonal changes, irritation from dental work, or a weakened immune system.
Are canker sores caused by a virus?
Canker sores can appear when your body is fighting any unrelated virus or infection, but canker sores themselves are not caused by a viral infection. They are not contagious.
Can canker sores test positive for herpes?
No, canker sores are not caused by the virus that causes herpes and cannot be mistaken for herpes.
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Robynn Lowe

Robynn Lowe is a board certified Family Nurse Practitioner with over 15 years in the medical field. Robynn received her Bachelor's and Master's degrees from Florida Atlantic University and has been practicing in rural family medicine since. Robynn is married to her college sweetheart, Raymond and they have three awesome children. When Robynn isn't with patients you can find her shopping, coaching her kids sports teams, or spending time on the water.