Stomatitis refers to inflammation of the mouth. It appears as either a red and swollen appearance of the mouth, with pain, or as discrete ulcers. Rarely, there are no ulcers, but only a burning sensation inside the mouth. Aphthous ulcers are the most common cause of stomatitis. These are acute painful ulcers on the tongue, or the inside of the lips or cheeks. They are also called canker sores, and have a reddish base, with a yellowish covering. They are not associated with other symptoms, and heal in a week or two. They usually appear first after the age of 10 years, and may reappear on and off over the next few years.

Causes of stomatitis
Stomatitis in general has several possible causes, which may overlap or interact with each other. Local causes of stomatitis include factors such as:
-- Trauma, as by ill-fitting dentures or other dental appliances.
-- Infections, either bacterial,  such as in syphilis, or viral, such as in Herpes Simplex and Herpes Zoster, ulcers caused by hand-foot-and-mouth disease due to the Coxsackie virus, or yeast infections.
-- Weakened or deficient immunity.
-- Chemical irritation by strong chemicals.
-- Recurrent aphthous ulcers, or stomatitis (RAS).
-- Medications such as sulfa drugs, antiepileptics and certain antibiotics.