Recurrent aphthous stomatitis !

Repeated painful, round mouth ulcers (canker sores) that heal on their own in one to two weeks. They are common and not contagious.

Updated 2026-11-01

Structures involved

Tap one to see what it is and open it in 3D.

Why it happens

What it is

The most common cause of recurrent oral ulcers. Aphthous ulcers are round or oval, shallow, painful ulcers with a yellow-grey fibrinous base and a red halo, found on the non-keratinised mucosa of the mouth (inner lips, cheeks, floor of the mouth, sides and underside of the tongue, soft palate). They come back at intervals in otherwise healthy people. The same type of ulcer can also be a sign of a systemic disease, which is then called complex aphthosis or aphthous-like ulcers.

Who gets it

It affects roughly one in five people at some point, with wide variation between populations. It usually begins in childhood or adolescence, is somewhat more frequent in women and tends to become milder after middle age. A family history is common. It is a frequent reason for consultation in general dentistry and primary care in Colombia and Latin America.

Causes

Cause not fully known; a dysregulated local immune response against the oral mucosa in genetically predisposed people
Local trauma: biting, dental work, rough toothbrushing, orthodontic appliances
Deficiencies of iron, vitamin B12 or folate
Emotional stress and lack of sleep
Hormonal changes, for example around menstruation
Some foods and toothpastes containing sodium lauryl sulphate; stopping smoking can unmask ulcers
Systemic disease: Behçet disease, coeliac disease, Crohn disease and ulcerative colitis, HIV infection, cyclic neutropenia and periodic fever syndromes (PFAPA)
Drugs such as NSAIDs, nicorandil and some chemotherapy agents (aphthous-like ulcers)

Risk factors

Family history of mouth ulcers
Female sex and younger age
Haematinic deficiency (iron, B12, folate)
Stress and local mucosal trauma
Coeliac disease or inflammatory bowel disease
Immunosuppression, including HIV infection

Pathophysiology

A trigger such as minor trauma activates a T-cell–mediated reaction against the epithelium of the non-keratinised mucosa. Cytokines such as TNF-alpha recruit inflammatory cells, the epithelium breaks down and an ulcer forms, covered by a fibrin membrane and surrounded by a red inflammatory halo. Keratinised mucosa (attached gingiva, hard palate, dorsum of the tongue) is usually spared, which helps distinguish aphthae from recurrent herpes simplex lesions.

Classification

Minor aphthae: the commonest type (about 80%), under 1 cm (usually under 5 mm), heal in 1–2 weeks without scarring
Major aphthae: over 1 cm, deeper, may reach the soft palate and pharynx, last weeks to months and heal with scarring
Herpetiform ulcers: dozens of pinpoint ulcers that may join together, heal in one to a few weeks; not caused by herpes virus
Simple aphthosis (healthy patient, few episodes) versus complex aphthosis (almost constant ulcers or associated systemic or genital lesions)

Symptoms and signs

Burning or tingling at a site for a day or two before the ulcer appears
One or more painful, round, shallow ulcers with a yellow-white base and a red border
Pain on eating, especially acidic, salty or spicy foods, and on talking or brushing
Ulcers on the inner lips, cheeks, tongue edges, floor of the mouth or soft palate
Usually no fever or general illness in simple aphthosis
Recurrence at intervals of weeks to months

Diagnosis

Clinical: Clinical diagnosis based on the typical appearance, location on non-keratinised mucosa, recurrence and healing pattern. A careful history and examination of the skin, eyes, genitals, joints and gut look for systemic associations.
Tests: No tests are needed for occasional minor aphthae. For frequent, severe or atypical ulcers: full blood count, ferritin, vitamin B12 and folate, coeliac serology (anti-tissue transglutaminase IgA with total IgA), HIV test and, if gut symptoms, faecal calprotectin and referral. Swabs or PCR for herpes simplex if vesicles or keratinised sites are involved; pathergy test and HLA testing are not routine. Biopsy for any persistent or atypical ulcer.
Imaging: Not needed for the oral lesions. Endoscopy or bowel imaging only if inflammatory bowel disease or coeliac disease is suspected.

Differential diagnosis

Recurrent herpes simplex (vesicles first, keratinised mucosa such as gums, hard palate and lip)
Hand, foot and mouth disease and herpangina in children
Behçet disease (recurrent oral plus genital ulcers, uveitis, skin lesions)
Traumatic ulcer
Erythema multiforme, Stevens–Johnson syndrome and other drug reactions
Oral lichen planus, pemphigus vulgaris and mucous membrane pemphigoid
Oral squamous cell carcinoma (persistent, indurated ulcer)
Syphilis and tuberculosis ulcers

Goal of treatment

Relieve pain, speed healing, reduce how often ulcers recur and identify and treat any underlying deficiency or systemic disease.

Treatment

Conservative: Avoid triggers such as acidic or spicy food, sharp food and toothpastes with sodium lauryl sulphate; use a soft toothbrush, keep good oral hygiene and maintain fluid intake.
Medical: Topical treatment is first line: protective pastes, topical anaesthetics and analgesic rinses for pain, antiseptic mouthwashes such as chlorhexidine, and topical corticosteroids applied early to shorten each episode.
Medical: Correct iron, vitamin B12 or folate deficiency and treat associated coeliac disease (gluten-free diet), inflammatory bowel disease or HIV.
Medical: Severe or frequent ulcers despite topical therapy: specialist care with systemic agents such as colchicine, short courses of oral corticosteroids, dapsone, or thalidomide or apremilast in selected cases.
Follow-up: Nursing and follow-up: assess pain and ability to eat and drink, offer soft, bland food, record frequency of episodes, and refer any ulcer lasting more than about three weeks for biopsy.

Complications

Pain causing poor intake, weight loss and dehydration, especially in children
Scarring and restricted mouth movement after major aphthae
Secondary infection of ulcers
Missed diagnosis of Behçet disease, coeliac disease, inflammatory bowel disease or oral cancer
Impact on quality of life, speech and work or school

Prognosis

Benign. Individual minor ulcers heal without scarring, and episodes usually become less frequent with age. There is no cure, but topical measures control most cases, and correcting a deficiency or treating an associated disease may stop the ulcers.

Prevention

Avoid known trigger foods and mouth trauma
Use a soft toothbrush and toothpaste without sodium lauryl sulphate
Manage stress and sleep
Correct nutritional deficiencies

Test yourself

Think of the answer, then tap the question to see it.

Where in the mouth do aphthous ulcers typically appear, and where do they usually not?

On non-keratinised mucosa (inner lips, cheeks, floor of mouth, ventral tongue, soft palate); they usually spare keratinised mucosa such as the attached gums and hard palate, where recurrent herpes is more typical.

Which type of aphthous ulcer heals with scarring?

Major aphthae: over 1 cm, deep and lasting weeks to months.

Which blood tests are reasonable in frequent or severe recurrent aphthae?

Full blood count, ferritin, vitamin B12, folate, coeliac serology and HIV testing when indicated.

Which systemic disease combines recurrent oral ulcers with genital ulcers and uveitis?

Behçet disease.

What should be done with a single mouth ulcer that has not healed after three weeks?

Refer for biopsy to exclude oral squamous cell carcinoma and other causes.

Add to my cards (5)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: Canker sore (MedlinePlus, US National Library of Medicine, 2026); Aphthous ulceration (aphthae, ulcers) (DermNet, 2025).

← All conditions

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.

Tongue highlighted on the Durgical 3D model