Aphthous ulcers, or canker sores, are common painful, shallow ulcers inside the mouth that heal on their own. Most are minor and recurrent, but large or persistent ulcers can point to a systemic disease.
Key symptoms
- Painful round sores inside the lips, cheeks or under the tongue
- Pain with spicy, salty or acidic foods
- Tingling or burning before the sore appears
- Recurrent episodes, sometimes after stress or minor injury
What you find on exam
- Round or oval shallow ulcer with a yellow-gray base and red rim
- Usually on the soft lining of the mouth, not the gums or hard palate
- Size and number: minor under 1 cm, major larger and deeper
- Look for genital ulcers, red eyes, rash or swollen lymph nodes
Tests
- Usually no tests needed
- Blood count, iron, B12 and folate if recurrent
- Celiac blood tests or bowel work-up if gut symptoms
- Biopsy for an ulcer lasting more than 3 weeks
Treatment basics
- Avoid trigger foods and mouth injury
- Topical anesthetic such as lidocaine gel for pain
- Topical steroid such as triamcinolone paste or dexamethasone rinse
- Correct deficiencies; colchicine for frequent severe cases
Red flags
- Ulcer lasting more than 3 weeks or with hard edges (rule out cancer)
- Genital ulcers or eye inflammation (think Behcet disease)
- Fever, weight loss, diarrhea or unable to drink
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations. Written by Making Synapses. Making Synapses is not affiliated with these organizations.