dental instruments and oral health

What are Canker Sores?

Canker sores (aphthous ulcers) appear as small, painful swellings on the lips or inside the mouth. A mixture of fluids, white blood cells, and bacteria cover the ulcer, creating a white 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 an ulcer is forming, it is not uncommon to feel irritation, tingling, and burning sensations around the infected area.

The sores can develop in a few different areas in and around the mouth, including:

  • The base of the gums
  • Insides of the cheeks
  • Inside of the lips (inner lip)
  • Under the tongue
  • On the soft palate

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:

Minor Sores

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

  • Typically less than 1 centimeter in diameter
  • Do not require treatment
  • Heal in 7 to 10 days
  • Do not scar

Major Sores

This type of canker sore is more severe and less common. Characteristics of major sores include:

  • Much bigger than minor 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

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 should not be confused with 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, such as kissing, hugging, handshakes, sharing drinks, and sharing utensils. Herpes is a lifelong disease with no cure. They emerge suddenly but typically disappear after four to twenty days.

Causes & Risk Factors

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 can cause aphthous ulcers. It is recommended to eat salads with raw onions, which are known to have healing properties and contain sulfur.

Hormonal Imbalances

Puberty, menopause, and menstruation 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 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.


In some cases, ulcers are associated with Crohn’s disease, which is a disease that affects the bowels.

Vitamin Deficiencies

To avoid canker sores, the body needs a proper balance of acidity, minerals, and alkalinity. Iron lysine, vitamin B12, and folic acid deficiencies have also been linked to canker sores.

Treatment Options

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 and Vanos
  • Hydrogen peroxide Orajel Antiseptic Mouth Sore Rinse and Peroxyl