DigestiveICD-10: K12.0Affects roughly 20% of people at some point; recurrent in many

Canker Sores

Also known as: Aphthous ulcers, Mouth ulcers, Aphthous stomatitis

Canker sores are small, shallow, painful ulcers that develop inside the mouth — on the inner cheeks, lips, tongue, or gums. Unlike cold sores, they are not caused by a virus and are not contagious. Most are minor and heal on their own within one to two weeks, but they can make eating and talking uncomfortable. They are very common and often recur, especially in times of stress or after minor mouth injury.

Symptoms

Round or oval sores with a white or yellow center and a red border
Painful spot inside the mouth, often before the sore appears
Tingling or burning a day or two before the ulcer forms
Pain that worsens with eating, especially acidic or spicy foods
In severe cases, fever or swollen lymph nodes

Causes

  • Minor mouth injury (biting the cheek, dental work, hard brushing)
  • Acidic or spicy foods and food sensitivities
  • Stress and hormonal changes
  • Nutritional deficiencies (vitamin B12, folate, iron, zinc)
  • Toothpaste containing sodium lauryl sulfate (SLS)
  • Underlying conditions (celiac disease, IBD, Behçet's, immune disorders)

Risk Factors

  • Family history of canker sores
  • Female sex
  • High stress levels
  • Nutritional deficiencies
  • Certain autoimmune and digestive conditions

Diagnosis

  • Visual examination of the mouth
  • Review of symptom pattern and recurrence
  • Blood tests for deficiencies if sores are frequent or severe
  • Testing for underlying conditions (celiac, IBD) when indicated

Treatment

  • Over-the-counter topical gels and pastes to numb and protect the sore
  • Antimicrobial or corticosteroid mouth rinses for severe cases
  • Salt water or baking soda rinses
  • Avoiding acidic, spicy, and abrasive foods while healing
  • Correcting nutritional deficiencies (B12, folate, iron, zinc)
  • Switching to an SLS-free toothpaste

Prevention

  • Use a soft toothbrush and brush gently
  • Avoid foods that trigger your sores
  • Manage stress
  • Choose SLS-free toothpaste if prone to sores
  • Maintain adequate vitamin and mineral intake

When to See a Doctor

  • Sores that are unusually large or last longer than two weeks
  • Frequent, recurring outbreaks
  • Sores accompanied by high fever or difficulty eating and drinking
  • Sores spreading to the lips or skin (may suggest cold sores instead)

Frequently Asked Questions

Related Conditions

Cold Sores (Oral Herpes)

Infectious

Oral Thrush (Oral Candidiasis)

Infectious

Gingivitis (Gum Disease)

Infectious

Celiac Disease

Autoimmune

Iron Deficiency Anemia

Metabolic

Related from the Supplement Library

Zinc

Strong

Mineral · Immune system support and T-cell function

Vitamin B12

Strong

Vitamin · Nervous system health and myelin formation

Folate

Strong

Vitamin · DNA synthesis and repair

L-Glutamine

Moderate

Amino Acid · Gut lining repair and intestinal integrity

Probiotics (Lactobacillus)

Strong

Probiotic · Gut microbiome balance and diversity

These supplements have been studied in relation to Canker Sores. Always consult your healthcare provider before starting any supplement, especially if you take medications.

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