Type of ulceration	Location	Size	Morphology	Vesicular phase	Pain	Frequency	Recurrence	Dermatomal pattern
Herpes zoster (shingles)	Hard or soft palate(cranial nerve V) or inner cheek (V3)	Usually small and discrete (1 to 2 mm)	Multiple, usually grouped	Initially	More severe than HSV ulcers	Rare	Rare	Typical
HSV infection	Immovable, keratinized (masticatory) mucosa	Usually small and discrete (1 to 2 mm)	Multiple, usually grouped	Initially	Mild	Uncommon intraorally	In up to 40 percent of patients	No
Primary syphilis	Loose, nonkeratinized mucosa	Large (3 to 20 mm)	Usually solitary with a raised border	None; begins as a papule	None	Uncommon	Rare	No
Recurrent aphthous stomatitis	Loose, nonkeratinized mucosa	Typically larger than an HSV ulcer	Usually solitary or few in number; may be clustered (herpetiform)	None	Sometimes intense	Common	Common	No
Recurrent aphthous stomatitis	Loose, nonkeratinized mucosa	Minor (80 percent of cases), 1 to 5 mm; major (10 percent of cases), 5 to 15 mm; herpetiform, 1 to 2 mm		None	Sometimes intense	Common	Common	No
Thermal trauma	Usually keratinized mucosa	Usually larger and nondiscrete	Variable	None	Mild	Common	With recurrent trauma	No