• Ask about possible precipitating factors.
• Ask about the frequency and duration of episodes, and the severity of any associated pain, as this will guide management.
• Ask about previously tried treatments (either over-the-counter or prescribed medicines).
• Consider alternative diagnoses or an underlying condition if the ulcers first occur later in life (e.g. more than 30 years of age), have lasted for longer than 3 weeks, affect atypical sites in the mouth (e.g. the palate or gums), affect extra-oral sites (e.g. genitalia), or are associated with systemic features (see Differential diagnosis).
• Consider investigations (e.g. full blood count, eosinophil sedimentation rate, ferritin, folate and vitamin B₁₂) to rule out underlying disease if ulceration frequently recurs.

• Frequency and duration of episodes, and severity of pain can be considered as follows:
• A single one-off ulcer is often caused by damage to the mouth, like biting the cheek, or damage to the gum with a toothbrush or a sharp tooth or filling. They usually go away once the source of the problem is treated.
• Some people have ulcers that occur just a few times a year and last for only a few days. Pain is usually tolerable.
• In some people ulcers occur at monthly intervals and are usually painful.
• Less commonly, ulcers occur continuously; by the time one ulcer heals, another has developed. These ulcers are usually extremely painful.

[Scully et al, 2003; Scully, 2006]

• Experts recommend identification and avoidance of precipitating factors where possible, to minimize recurrence [Scully et al, 2002].
• Frequency, duration, and severity of pain will help to determine the management of aphthous ulcers [Scully et al, 2003].
• Onset of aphthous ulceration after 30 years of age, systemic symptoms, and presence of extra-oral ulcers suggest that the ulcers are part of a more complex disorder that warrants further investigation [Scully et al, 2003].