Aphthous Ulcers (Canker Sores) - Symptoms, Causes & Treatment
By ScanSkinAI Editorial Team✓ Reviewed for medical safetyLast updated June 2026
Painful, shallow ulcers that occur inside the mouth on the tongue, lips, or cheeks. They're not contagious and usually heal within 1-2 weeks without treatment.
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Quick Answer
Aphthous ulcers, commonly known as canker sores, are painful, shallow sores that appear on the inner lips, cheeks, or tongue. They typically have a white or yellow center surrounded by a red border. Unlike cold sores, they occur strictly inside the mouth and are completely non-contagious. Minor mouth injuries, stress, spicy foods, or nutritional deficiencies can trigger them. Most canker sores clear up on their own within one to two weeks without treatment, though over-the-counter topical gels and mouthwashes can help manage the daily discomfort while they heal.
Clinical Context
Aphthous ulcers are the most common oral mucosal lesions, affecting 20% of the population. Unlike cold sores, they're not contagious and occur inside the mouth. Recurrent ulcers may indicate nutritional deficiencies or systemic disease.
Symptoms
- Painful round or oval sores in mouth
- White or yellow center with red border
- Tingling before sore appears
- Difficulty eating or talking
- Usually heal in 1-2 weeks
Severity & Progression
Causes & Risk Factors
- Minor mouth injury
- Stress
- Certain foods (citrus, spicy)
- Nutritional deficiencies
- Immune disorders
- Not infectious
Treatment & Management
- Topical anesthetics
- Antimicrobial mouthwash
- Corticosteroid gels
- Avoiding trigger foods
- Pain relievers
When to See a Doctor
If sores are unusually large, don't heal within 2 weeks, occur frequently, or are accompanied by fever
Frequently Asked Questions
Are canker sores the same thing as cold sores?
No, they are entirely different. Canker sores occur exclusively inside the mouth and are not caused by a virus, meaning they are completely non-contagious. You cannot spread them through kissing or sharing drinks. Cold sores, on the other hand, typically form on the outside of the lips and are contagious because they are caused by a virus.
How can I tell if I have a canker sore?
You will usually notice a distinct tingling or burning sensation a day or two before the sore appears. Once formed, it looks like a round or oval shallow ulcer with a white or yellow center and a prominent red border. They are usually quite painful, especially when you are eating, drinking, or talking.
Why do I keep getting these painful mouth ulcers?
Recurrent canker sores can be triggered by multiple factors. Everyday stress, minor mouth injuries from accidental biting or aggressive brushing, and eating acidic or highly spiced foods are very common culprits. If you get them frequently, it could also point to an underlying issue like a nutritional deficiency or an immune disorder.
What is the quickest way to heal a canker sore?
Most minor canker sores heal naturally within one to two weeks. While you cannot instantly cure them, you can significantly reduce the pain and speed up comfort by using over-the-counter topical anesthetics, corticosteroid gels, or antimicrobial mouthwashes. During the healing process, it is best to avoid acidic, spicy, or rough-textured foods that will further irritate the sensitive tissue.
Will a canker sore leave a permanent scar inside my mouth?
The vast majority of canker sores are classified as minor, meaning they measure less than one centimeter and will heal completely without leaving any scars. However, if you develop a major aphthous ulcer, which is larger, deeper, and takes a few weeks to heal, there is a chance it may leave some minor scarring on the oral tissue.
Is there anything I can do to stop getting canker sores?
While you might not be able to prevent them entirely, you can reduce your risk by avoiding personal triggers. Try cutting back on acidic items like citrus fruits or tomatoes, and minimize spicy foods. Brushing your teeth gently with a soft-bristled toothbrush prevents accidental scrapes. Managing your daily stress levels and ensuring you eat a well-balanced diet also help.
When should I actually see a doctor or dentist for a mouth sore?
You should seek medical evaluation if you develop unusually large mouth sores, or if the sores do not show signs of healing after two weeks. It is also important to consult a healthcare provider if the pain is extreme, you have difficulty drinking enough fluids, the sores occur alongside a fever, or they keep returning aggressively.
How can ScanSkinAI help with aphthous ulcers?
ScanSkinAI provides an accessible screening tool to visually analyze oral sores and help you identify potential conditions like aphthous ulcers based on their appearance. However, it is important to remember that our artificial intelligence is a screening aid only and cannot provide a definitive medical diagnosis. Always consult a dentist or doctor for proper evaluation and care.
Medical References
Information on this page is sourced from and verified against reputable medical resources:
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Medical Disclaimer: This information is for educational purposes only and is not intended as medical advice. The content on this page should not be used to diagnose or treat any health problem. Always consult with a qualified healthcare professional for proper medical evaluation, diagnosis, and treatment of your condition.