Recurrent aphthous ulcers: most have no identifiable cause, but some do

The recurrent aphthous ulcer is among the commonest oral lesions and one on which patients receive the most contradictory explanations, often attributed generically to stress.

Three forms are distinguished. Minor ulcers, under a centimetre, heal within one or two weeks without scarring, and account for the great majority of cases.

Major ulcers exceed a centimetre, are deeper, heal over weeks and may scar. Herpetiform ulcers are numerous pinpoint lesions that coalesce, despite the name bearing no relation to herpes.

The distinction matters because major and herpetiform forms warrant fuller investigation, while isolated minor ulcers in an otherwise healthy patient rarely conceal anything.

The deficiencies to exclude when ulcers are frequent are iron, folate, vitamin B12 and zinc. These are simple tests and correcting a deficiency may resolve the problem.

Coeliac disease should be considered, because recurrent ulcers can be its most evident manifestation in the absence of marked intestinal symptoms.

One practical detail is often decisive and concerns toothpaste. Sodium lauryl sulphate, the surfactant that produces foam, is associated in some studies with increased ulcer frequency in susceptible individuals.

Trying an SLS-free toothpaste for a few months is a zero-cost intervention that reduces recurrence in a proportion of patients, and is worth suggesting before more complex therapies.

Repeated local trauma is a concrete precipitant: a sharp margin, a denture clasp, aggressive brushing. Correcting the trauma removes the recurrent site.

Treatment of common forms is symptomatic. Gels with local anaesthetic cover pain during meals; topical corticosteroids reduce duration and severity if applied at onset.

Chlorhexidine mouthwash does not cure the ulcer but prevents bacterial superinfection, and indirectly reduces pain by keeping the lesion clean.

Certain signs indicate looking further: lesions not healing within three weeks, ulcers accompanied by genital or ocular lesions, onset in later adult life, or association with systemic symptoms. These call for investigation rather than another gel.

In summary: isolated minor forms rarely have an identifiable cause, deficiencies should be excluded when ulcers are frequent, SLS-free toothpaste is a free trial, and any lesion not healing within three weeks needs investigation.