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Canker Sores Symptoms & Diagnosis


If you experience any of these symptoms, do not assume it is due to aphthous ulcers. Mouth sores similar to these may be caused by other more serious conditions.

Aphthous ulcers have various sizes. They typically occur on the inner surface of the cheeks and lips, on the tongue, and the soft palate. Usually they are an open, shallow grayish sore with a slightly raised, yellowish-white border, surrounded by a red border.

Some people get aphthous ulcers two or three times per year. Others develop lesions continually one after another. Usually the most painful phase is the first 3 to 4 days, and then the sores begin to heal.

  • Minor ulcers (the most common form)
    • Less than one centimeter in diameter
    • Usually last 7 to 14 days
    • Heal without scarring
  • Major ulcers
    • Greater than one centimeter in diameter
    • Last several weeks or even months
    • Heal with scarring


Your doctor will ask about your symptoms and medical history. A physical exam will be performed. Looking at the sores is the primary way to tell the difference between aphthous ulcers and other more serious mouth sores. In certain cases, the doctor may take a small sample of a sore for microscopic tissue examination (a biopsy ) or order cultures or blood tests.

It is especially important to examine mouth sores that do not heal within two weeks. They may be a sign of cancer.

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition. Copyright © 2020 EBSCO Publishing All rights reserved.

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