Understanding Mouth Ulcers (Canker Sores): Symptoms & Causes

What Are Canker Sores (Aphthous Ulcers)?

Shallow, round/oval ulcers with a yellow-white fibrinous center and erythematous halo on non-keratinized oral mucosa (buccal/labial mucosa, tongue, floor of mouth, soft palate).

Types

Type	Size	Healing	Scarring
Minor (80%)	<1 cm	7–10 days	No
Major (10–15%)	>1 cm	Weeks–months	Yes
Herpetiform (5–10%)	1–3 mm (clusters of 10–100)	7–10 days	Rare

Triggers

• Trauma (biting, dental work, sharp food)
• Stress, sleep deprivation
• Nutritional deficiencies (iron, folate, B12, zinc)
• Hormonal changes (menstrual cycle)
• Food sensitivities (citrus, chocolate, coffee, nuts, gluten)
• SLS (sodium lauryl sulfate) in toothpaste
• Medications (NSAIDs, beta-blockers, nicorandil)
• Systemic diseases (Behçet's, celiac, IBD, HIV, MAGIC syndrome)

Management

• Topical corticosteroids (triamcinolone 0.1% in Orabase, fluocinonide gel)
• Topical anesthetics (benzocaine, lidocaine)
• Antimicrobial rinses (chlorhexidine)
• Sucralfate slurry, honey, aloe vera
• Systemic: colchicine, dapsone, thalidomide (refractory); treat underlying cause.

When to See a Doctor

• Ulcers >2 weeks, unusually large, spreading
• High fever, difficulty swallowing
• Recurrent (>3–4×/year) or continuous
• Associated systemic symptoms