Seek prompt medical care if mouth sores make it extremely difficult to eat or drink, or occur with a high fever.
Self-care guide
Canker sores
Small painful ulcers inside the mouth that are usually benign and self-limited, commonly called canker sores or aphthous ulcers.
Step 1 · First-line care
What to do first
Most ordinary canker sores heal on their own within about 1 to 2 weeks. Avoid local trauma and foods that clearly aggravate the ulcer. A saline mouth rinse and pharmacist-recommended pain-relief, antimicrobial, or corticosteroid oral products may help symptoms when appropriate. No herbal product is promoted because current botanical evidence is heterogeneous and does not establish a reliable preparation-specific advantage.
Step 2 · Safety
When to get medical help
Get medical help if arrange medical or dental assessment for a mouth ulcer lasting longer than 3 weeks, or for unusually large, recurring, atypical, or uncontrolled painful mouth sores.
Extra caution: Children with poor intake or dehydration, immunocompromised people, people receiving cancer therapy, and people with persistent or atypical oral lesions need earlier clinical evaluation. Canker sores should not be confused with cold sores on the lip, traumatic ulcers, dental infection, or persistent lesions requiring cancer assessment.