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Updated on January 20, 2023
10 min read

Canker Sores: Types, Causes & How To Get Rid of Them

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What are Canker Sores? Where Do They Form?

Canker sores (aphthous ulcers) are small, shallow, and painful lesions on the lips or inside the mouth. They appear as small round lesions with a white center (scientifically known as slough) and a red border (inflamed tissue).

The sores are a mixture of fluids, white blood cells, and bacteria. In some cases, canker sores can be as large as a quarter.

Canker sores don't form outside of the mouth; instead, they form in the following areas:

  • The base of the gums
  • Inside the cheeks
  • Inside of the lips (inner lip)
  • On the soft palate (back of the roof of the mouth)
  • On or under the tongue
Canker Sores

Canker Sore Stages

The exact duration of a canker sore can vary from person to person. However, there is a timeline that can serve as a guide for what to expect:

  • Prodromal stage: The stage before a canker sore appears, lasts for about 1-3 days
  • Ulcer stage: A fully formed ulcer that tends to last for 3-6 days, in some cases, it can be longer
  • Healing stage: The healing stage can last for 7-14 days or longer, depending on the type of canker sore

Side-Effects of a Canker Sore

During the formation of a canker sore, it is not uncommon to feel some discomfort around the infected area. This includes:

  • Irritation
  • Tingling
  • Burning sensations

If you have a severe case of canker sores, you may experience other symptoms, which include:

  • Swollen lymph nodes
  • Fever
  • Sluggishness
young woman looking anxious scaled

3 Types of Canker Sores

There are three types of canker sores. They are distinguished by their size, shape, and pain level:

1. Minor Sores

Minor canker sores are the most common type, affecting more than 80 percent of sore sufferers. Characteristics of minor canker sores:

  • Typically less than 5 mm in diameter
  • Do not require treatment
  • Heal in 7 to 14 days 5
  • Do not scar

2. Major Sores

Major canker sores are more severe and appear less commonly than minor ones. Characteristics of a major canker sore includes:

  • Over 1 centimeter in diameter
  • Often require treatment
  • Do not heal for two or more weeks
  • Can last for weeks or months 5
  • Typically extremely painful
  • May form a scar

3. Herpetiform Sores

Herpetiform sores are the least common type of canker sore. Characteristics include:

  • Appear as a cluster of small sores
  • May require treatment
  • Individual sores are less than a few millimeters in diameter
  • Small sores often form into larger ulcers
  • Typically extremely painful
  • Heal in about one month 5

What Canker Sores Look Like (Pictures)

Medical Images of Canker Sores

canker sore back of mouth
canker sore inner lip

What Causes Canker Sores?

Common causes of canker sores include:

Poor Oral Hygiene

Poor oral hygiene allows bacteria to develop in the mouth. Maintaining good oral hygiene prevents this from happening. Keeping the mouth healthy includes:

  • Brushing twice a day
  • Flossing at least once a day
  • Rinsing the mouth regularly

Limiting hard, crunchy, unhealthy, or irritating foods (acidic) is also helpful in avoiding canker sores.

Oral Injuries

Oral injuries have many causes. These include:

  • After having dental work done
  • Sports injuries
  • Excessively brushing the teeth
  • Small cuts
  • Accidental cheek biting
  • Poor-fitting dentures
  • Braces
  • Fractures

Sustaining an oral injury through any of these means can increase the risk of developing canker sores.3, 5

Food Allergies

Allergic reactions to food can cause the formation of canker sores. These foods include:

  • Acidic foods
  • Spicy foods
  • Dairy
  • Nuts
  • Gluten


Toothpaste containing sodium lauryl sulfate (SLS) can cause canker sores. The ingredient is known to irritate the tissues inside the mouth and gums. If ulcers are recurrent, toothpaste is likely the culprit.

Nutritional Deficiencies

Excessive intake of sugar, processed foods, and citrus fruits can cause aphthous ulcers. It is recommended to eat salads with raw onions because they contain sulfur. Sulfur has antibacterial effects.

Hormonal Imbalances

Hormonal imbalances can increase inflammation in and around the mouth. The hormonal imbalances that can cause canker sores includes:

  • Puberty
  • Menopause
  • Menstrual cycles

HIV Infection

Canker sores are not a symptom of HIV (human immunodeficiency virus), which is a virus that breaks down cells in the immune system. Although, people with HIV/AIDS may develop severe sores more frequently than those without the virus.

Stress and Fatigue

Emotional or physical stress can cause canker sores in some people because excessive stress increases inflammation.


Frequent canker sores are associated with certain diseases and chronic health conditions. These health conditions include, but are not limited to:

  • Inflammatory bowel diseases
  • Celiac disease (an intestinal disorder caused by gluten intolerance)
  • Behcet's disease (causes inflammation around the entire body)
  • Lupus (an autoimmune disease that causes the body to attack the organs and tissues)

Vitamin Deficiencies

The body needs a proper balance of acidity, minerals, and alkalinity to avoid canker sores. You may get canker sores if you're deficient in:3, 4

  • Iron
  • Zinc
  • Vitamin B12
  • Folic acid
  • Calcium

Can You Get Canker Sores on Your Tongue?

Yes, you can get tongue sores. These are typically caused by:

  • Mouth injures
  • Braces
  • Dental work
  • Sports accidents
  • Brushing your teeth too hard

What Gets Rid of Canker Sores Fast?

Regardless of your treatment, canker sores do not disappear within 24 hours. However, there are ways to avoid prolonging the healing stage.

You can use over-the-counter drugs like:

  • Fluocinonide Lidex (Fluocinonide) and Vanos mouth rinse
  • Hydrogen peroxide products Orajel Antiseptic Mouth Sore Rinse™ and Colgate® Peroxyl®
  • Tetracycline – A medication typically prescribed if you frequently get canker sores
  • Ibuprofen – ibuprofen or other over-the-counter (OTC) pain relievers can reduce swelling, discomfort, and pain

Doctors advise against popping canker sores. This can be extremely painful.

It's important to know that one possible side effect of tetracycline is a fungal infection called oral thrush. Ironically, oral thrush can lead to mouth sores.

7 Ways to Prevent Canker Sores

In most cases, canker sores are a natural part of life. However, if you develop sores frequently, there are ways to prevent them from developing. Prevention tips include:

  1. Avoid or limit your intake of spicy foods, acidic fruits, and other acidic drinks (e.g., coffee and fruit juices)
  2. Take a multivitamin every day
  3. Take a 1000 mcg dose of vitamin B-12 at night to reduce and prevent canker sore breakouts
  4. Do not use dental products that contain sodium lauryl sulfate
  5. Chew less gum to prevent irritation
  6. Brush and floss your teeth regularly to remove bacteria, food particles, and plaque in your mouth
  7. Use a soft-bristled toothbrush and try to brush after each meal (if you get canker sores often)

Natural Canker Sore Remedies

There are a few natural home remedies that can be used to help speed up the healing process and decrease irritation. Natural remedies for canker sore speed healing include:

  • Suck on ice chips and/or Zinc lozenges to relieve pain and discomfort
  • Use a mouth rinse and toothpaste that does not contain sodium lauryl sulfate
  • Mix liquid Benadryl with magnesia and use it as a mouth rinse
  • Rinse your mouth a few times each day with warm salt water or a baking soda rinse (1 teaspoon per 1/2 cup of warm water) for a few minutes
  • Eat salads that contain raw onions
  • Drink chamomile tea to soothe canker sore discomfort (German chamomile contains anti-inflammatory and antiseptic properties)
  • A medication called Orabase can help keep your canker sore from becoming more painful when brushing your teeth, eating, or drinking

Canker Sores vs. Cold Sores (Herpes)

Canker sores are not cold sores. They are noncontagious inflammations rather than infections.

The herpes simplex virus type 1 (HSV-1) is a highly contagious infection that causes cold sores (fever blisters). Cold sores are small, fluid-filled blisters that usually appear on the hard part of the gums or the outside of the lips.

HSV-1 spreads through close personal contact. This includes:

  • Kissing
  • Hugging
  • Handshaking
  • Sharing drinks
  • Sharing utensils

Herpes is a lifelong disease with no cure.

Are Canker Sores Contagious?

Canker sores are not contagious. You cannot get a canker sore by sharing food, utensils, drinks, or kissing an individual with a canker sore.

A cold sore (HSV-1) is contagious if an oozing blister is present. However, the sore is not contagious if it has completely scabbed.

When to See a Doctor

Consult your doctor if your canker sore is large and lasts for longer than two weeks. Also, visit your doctor if the pain worsens and you can't seem to control it with home remedies.

Diagnosing Canker Sores

Tests are not needed to diagnose a canker sore. Your dentist or doctor may recommend blood work if the ulcer(s) does not disappear on its own or if there is a severe breakout present. You may also benefit from a vitamin deficiency test if you experience frequent sores.

Are Canker Sores Harmful?

Canker sores normally do not have any complications or risks if they are caused by natural factors. In rare cases, canker sores can be an early sign of oral cancer (mouth cancer). Ulcers caused by oral cancer are typically painful, thicken over time, and do not disappear on their own.

Potential Complications of Canker Sores

Some possible complications of canker sores include:

  • Fatigue
  • Cellulitis (a bacterial skin infection)
  • Fever
  • Sores that appear outside of the mouth
  • Pain while brushing your teeth, eating, and/or talking


Canker sores are small, painful lesions that develop on the inside of the mouth. They can be small or large and typically have a white, gray, yellow, or red border.

There are three types of canker sores and each one can vary in size, discomfort, and healing duration:

  • Minor sores can heal within two weeks
  • Major sores can last for months
  • Herpetiform sores require treatment

Most canker sores typically go away on their own within a week. If a canker sore lasts longer than two weeks, seek treatment.

Frequently Asked Questsion

Here are some frequently asked questions about canker sores:

Can you pop a canker sore?

You cannot pop a canker sore. They are shallow wounds, not pimples or blisters. It would be very painful to try and pop a canker sore.

What is the best mouthwash for canker sores?

Orajel™ Antiseptic Mouth Sore Rinse is the best mouthwash for canker sores because it aids in the healing process. Orajel also soothes cheek bites, gum irritation, and denture discomfort.

How long do canker sores last?

Canker sores can take anywhere between 1 to 6 weeks to heal completely. However, they typically hurt for 7 to 10 days. Minor canker sores heal in about 1 to 3 weeks. Major canker sores may not heal for up to 6 weeks. Another canker sore can also develop before the first one heals.

Does drinking milk help canker sores?

Milk of magnesia can help reduce canker sore pain and discomfort, while also speeding up the healing process.

Does putting salt on a canker sore help?

Yes, saltwater has anti-bacterial properties that promote healing and help reduce pain symptoms. Rinse with a saltwater mixture (1 teaspoon salt per 1/2 cup warm water) 1-3 times today to help your canker sore heal. You may experience slight pain or discomfort while swishing.

How do you heal a canker sore fast?

Hydrogen peroxide products such as Orajel Antiseptic Mouth Sore Rinse can help heal canker sores quickly.

Can you kiss someone with a canker sore?

Canker sores are not contagious, so they cannot be spread through kissing. However, you may experience discomfort or pain from friction.

Do canker sores spread?

No. Canker sores are not contagious. Cold sores are contagious.

Is a canker sore a virus?

No, canker sores are lesions and are not associated with any viruses. Unlike cold sores, which are associated with viruses.

What is the best medication for canker sores?

Use hydrogen peroxide products such as Orajel Antiseptic Mouth Sore Rinse to help heal your canker sores. OTC pain medications such as ibuprofen can help reduce pain. For frequent cold sores, talk to your dentist, they may prescribe you tetracycline.

What vitamins help prevent canker sores?

Taking a 1000 mcg dose of vitamin B-12 at night can help reduce and prevent canker sore breakouts.

When should I be concerned about a canker sore?

Visit your doctor if you get recurring, very large, or persistent canker sores (lasting two or more weeks).

Last updated on January 20, 2023
6 Sources Cited
Last updated on January 20, 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. Balch, Phyllis A. Prescription for Nutritional Healing. Avery, a Member of Penguin Group (USA) Inc., 2010.
  2. Zand et al. Smart Medicine for a Healthier Child: a Practical A-to-Z Reference to Natural and Conventional Treatments for Infants and Children. Avery, 2004.
  3. Aphthous Stomatitis.” Aphthous Stomatitis - an Overview | ScienceDirect Topics.
  4. Edgar et al. “Recurrent Aphthous Stomatitis: A Review.” The Journal of Clinical and Aesthetic Dermatology, Matrix Medical Communications, Mar. 2017.
  5. Scully, C. and Shotts, R. “Mouth Ulcers and Other Causes of Orofacial Soreness and Pain.” Western Journal of Medicine, Copyright 2001 BMJ Publishing Group, 2001.
  6. FPRP, 1Bronx Lebanon Hospital Center. “Canker Sores/Recurrent Aphthous Stomatitis (RAS) : Evidence-Based Practice.” LWW.
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