Canker sores and irritation
Canker sores usually appear on movable tissue inside the mouth and can be tender. Biting, vigorous brushing, hot food, or a repeatedly rubbing denture edge can also irritate tissue. Appearance alone cannot confirm a diagnosis.
Canker sores and cold sores differ
Canker sores develop inside the mouth and are not contagious. Cold sores often begin as blisters near the lip and may be contagious. If you are unsure, seek professional advice.
Care and when to seek an assessment
A soft toothbrush and avoiding foods that irritate the area may help with comfort. A lesion lasting more than two weeks, recurring, becoming firm or bleeding easily, or occurring with fever or neck swelling should be assessed by a dentist or clinician.
Based on: Doctor Afra · Mouth ulcers and canker sores: when to see a dentist