Stomatitis washes away antigens and acts as a barrier. The oral mucosa is also more vascular (has a better blood supply) than skin, meaning that any antigens are more quickly removed from the area by the circulation. Finally, there is substantially less keratin in oral mucosa, meaning that there is less likelihood that haptens will form. Allergic contact stomatitis appears as non-specific inflammation, so it may be mistaken for chronic physical irritation. There may be burning or soreness of the mouth and ulceration. Chronic exposure to the allergen may result in a lichenoid lesion. Plasma cell gingivitis may also occur, which
Aphthous stomatitis antigens, but this is unclear. Nicotine is also known to stimulate production of adrenal steroids and reduce production of TNF-α, interleukin-1 and interleukin-6. Smokeless tobacco products also seem to protect against aphthous stomatitis. Cessation of smoking is known to sometimes precede the onset of aphthous stomatitis in people previously unaffected, or exacerbate the condition in those who were already experiencing aphthous ulceration. Despite this correlation, starting smoking again does not usually lessen the condition. Various antigenic triggers have been implicated as a trigger, including L forms of streptococci, herpes simplex virus, varicella-zoster virus, adenovirus, and cytomegalovirus. Some people with aphthous