Canker Sore: What It Is

A canker sore or aphthous ulcer is a lesion inside the mouth, appearing as a small white spot with a red border. It is not contagious, unlike a cold sore, which appears outside the mouth.

Canker sore


Pain typically disappears in about ten days, but healing may take up to three weeks. There is no known cure for a canker sore, other than time. However, soothing remedies are available.

Remedies For Canker Sore

To control bacterial infection, brush and floss as usual. Rinsing with hydrogen peroxide also helps to kill oral bacteria.

Rinsing with half salted water, half hydrogen peroxide may soothe the sore. Another option is to apply Milk of Magnesia to the spot with a cotton swab. Some claim applying a wet black tea bag to the canker sore also alleviates pain.

Causes Of Canker Sores

The causes of canker sores are poorly understood. However, canker sores may arise following:

  • Injury to the mouth (braces or dentures, aggressive brushing or dental work, biting self)
  • Emotional stress
  • Immune deficiency
  • Changes in hormones (menstrual period)
  • Acidic foods (lemon, orange, tomato, strawberry)