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

Symptoms of Canker Sores & Where They Develop

Canker sores (aphthous ulcers) appear as small, painful swellings on the lips or inside the mouth. The painful sores are covered by a mixture of fluids, white blood cells, and bacteria. They typically have a white, gray, or yellowish film with a red border.

In the beginning stages, the sores may appear as small red dots. In some cases, they can be as large as a quarter. As a canker sore is forming, it is not uncommon to feel irritation, tingling, and burning sensations around the infected area.

Canker sores do not develop outside of the mouth. Rather, the sores can develop in a few different areas in and around the mouth, including:

  • The base of the gums
  • Inside of 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 can also develop on or under the tongue. These sores are typically caused by mouth injuries, braces, dental work, sports accidents, or brushing your teeth too hard.

ulcer sore

3 Types of Canker Sores

There are three types of canker sores, including minor sores, major sores, and herpetiform 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 1 centimeter in diameter
  • Do not require treatment
  • Heal in 7 to 10 days
  • Do not scar

2. Major Sores

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

  • They are much bigger than minor canker sores (over 1 centimeter in diameter)
  • Often require treatment
  • Do not heal for two or more weeks
  • Can last for up to 45 days
  • 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 ten days

Canker Sores vs. Cold Sores (Herpes)

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

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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, such as kissing, hugging, handshakes, sharing drinks, and 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 who has 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.


Cause of Canker Sores

The cause of a canker sore is difficult to pinpoint, but it could be linked to food allergies, acidic conditions, oral health habits, or even a small cut. Women are also more likely to develop canker sores, but the reason why is unknown. Common risk factors include:

Poor Oral Hygiene

Brushing twice a day, flossing at least once a day, and rinsing the mouth regularly kills bacteria and keeps the mouth healthy. To avoid them, it is also important to limit hard, crunchy, unhealthy, or irritating foods (acidic).

Injury or Trauma

Canker sores may develop after having dental work done. Sports injuries, brushing the teeth excessively, small cuts, and accidental cheek biting can also cause them.

Food Allergies

Acidic foods, spicy foods, coffee, strawberries, eggs, nuts, eggplants, cheese, tomatoes, and gluten may cause allergic reactions in some people. These reactions can lead to the formation of canker sores.


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, which has antibacterial effects.

Hormonal Imbalances

Puberty, menopause, and menstrual cycles can increase inflammation in and around the mouth.

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 – such as Crohn’s disease and ulcerative colitis
  • Celiac disease – a severe intestinal disorder caused by gluten intolerance
  • Behcet's disease – causes inflammation around the entire body (including the mouth)
  • Lupus – an autoimmune disease that causes your body to attack its own organs and tissues
  • A compromised immune system – when someone has a reduced immune response to fighting off infections

Vitamin Deficiencies

To avoid canker sores, the body needs a proper balance of acidity, minerals, and alkalinity. Iron, zinc, vitamin B12, and folic acid deficiencies have been linked to canker sores. Calcium deficiencies also cause canker sores and can even make the sores worse.


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 there is a severe breakout present. You may also benefit from a vitamin deficiency test if you experience frequent sores.


How To Get Rid of Canker Sores Fast

Minor canker sores typically go away on their own within a week. Although, if major canker sores develop, it is important to seek treatment. Over-the-counter products are usually recommended, including:

  • Fluocinonide Lidex (Fluocinonide) and Vanos mouth rinse
  • Hydrogen peroxide products Orajel Antiseptic Mouth Sore Rinse™ and Colgate® Peroxyl®
  • Tetracycline – if you get frequent canker sores, your doctor or dentist may prescribe you tetracycline. However, one possible side effect of this medication is a fungal infection called oral thrush. Thrush, ironically, can lead to mouth sores.
  • Ibuprofen – you can take ibuprofen or other over-the-counter (OTC) pain relievers to reduce swelling, discomfort, and pain

Natural Remedies for Fast Relief

Canker sores usually disappear on their own within 7 to 10 days. There are a few natural home remedies that can be used to help speed up the healing process and decrease irritation. Natural remedies for fast canker sore relief 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 baking soda (1 teaspoon baking soda per 1/2 cup warm water)
  • Eat salads that contain raw onions

Prevention Tips

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:

  • Avoid or limit your intake of spicy foods, acidic fruits, and other acidic drinks (e.g., coffee and fruit juices)
  • Take a multivitamin every day
  • Do not use dental products that contain sodium lauryl sulfate
  • Chew less gum to prevent irritation
  • Brush and floss your teeth regularly to remove bacteria, food particles, and plaque in your mouth
  • Use a soft-bristled toothbrush and try to brush after each meal (if you get canker sores often)

Possible Complications & Risk Factors

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.


Balch, Phyllis A. Prescription for Nutritional Healing. Avery, a Member of Penguin Group (USA) Inc., 2010.

Zand, Janet, 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.

Updated on: June 29, 2020
Alyssa Hill
Medically Reviewed: September 25, 2019
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Lara Coseo