<unk>  is an inflammation of the mucous lining of any structure in the mouth, which may involve the cheeks, gums, tongue, lips, throat, and/or the roof or floor of the mouth.  The inflammation can be the result of conditions within the mouth itself, such as poor oral hygiene, poorly fitted dentures, or mouth burns from hot food or drinks. It may also be caused by conditions that affect the entire body, such as medications, allergic reactions, or infections. A form of<unk>  known as<unk>  nicotina can be caused by smoking cigars, cigarettes, and/or pipes, and is characterized by small red bumps on the roof of the mouth.
When<unk>  also involves an inflammation of the gingiva, it is called gingivostomatitis. Irritation and fissuring in the corners of the lips is termed angular<unk>  or angular cheilitis. In children, a common cause of angular<unk>  is repeated lip-licking; in adults, it may be a sign of underlying iron deficiency anemia, or vitamin B deficiencies (e.g., B2-riboflavin, B9-folate, or B12-cobalamins), which in turn may be evidence of poor dietary habits or malnutrition (e.g., celiac disease).
There is no established classification system for<unk> .<unk>  can be classified on the basis of aetiology or on the basis of the pathogens involved. The infectious and non-infectious types of<unk>  may include:
Infectious
Bacterial
Necrotizing ulcerative<unk>  or<unk>  gangrenosa (Noma)
Viral
Herpetic gingivostomatitis
Vincent's<unk>  (Trench Mouth)
Fungal
Candidal<unk> 
Non-infectious
Autoimmune
Aphthous<unk> 
SLE
Pemphigus vulgaris
Bullous pemphigoid
SJS
Pyostomatitis vegetans
Drug-induced
Chemotherapy
Antibiotics
Antihistamine
Monoclonal antibodies
Antirheumatic agents
Irritant induced
Denture<unk> 
Contact<unk> <unk>  nicotina
Other causes
Tumors
Black hairy tongue
Burning  mouth syndrome
Migratory<unk>  or geographic<unk> 
Ulcerative or chronic ulcerative<unk> 
Bacterial
Necrotizing ulcerative<unk>  or<unk>  gangrenosa (Noma)
Viral
Herpetic gingivostomatitis
Vincent's<unk>  (Trench Mouth)
Fungal
Candidal<unk> 
Necrotizing ulcerative<unk>  or<unk>  gangrenosa (Noma)
Herpetic gingivostomatitis
Vincent's<unk>  (Trench Mouth)
Candidal<unk> 
Autoimmune
Aphthous<unk> 
SLE
Pemphigus vulgaris
Bullous pemphigoid
SJS
Pyostomatitis vegetans
Drug-induced
Chemotherapy
Antibiotics
Antihistamine
Monoclonal antibodies
Antirheumatic agents
Irritant induced
Denture<unk> 
Contact<unk> <unk>  nicotina
Other causes
Tumors
Black hairy tongue
Burning  mouth syndrome
Migratory<unk>  or geographic<unk> 
Ulcerative or chronic ulcerative<unk> 
Aphthous<unk> 
SLE
Pemphigus vulgaris
Bullous pemphigoid
SJS
Pyostomatitis vegetans
Chemotherapy
Antibiotics
Antihistamine
Monoclonal antibodies
Antirheumatic agents
Denture<unk> 
Contact<unk> <unk>  nicotina
Tumors
Black hairy tongue
Burning  mouth syndrome
Migratory<unk>  or geographic<unk> 
Ulcerative or chronic ulcerative<unk> <unk>  is the inflammation of the mucosal surfaces in the mouth. Various factors can contribute to the pathogenesis of<unk>  depending on the type of<unk> .
A definitive pathogenesis for aphthous<unk>  is not known. The proposed mechanism involves immune system abnormalities and the presence of autoimmune antibodies. It is thought to be caused by some types of cytokine and T cell accumulation, manifesting as a defective cell-mediated arm of immunity. Recurrence is very common in aphthous ulcers.
Various causes, including herpes virus, lack of oral hygiene, and nutritional deficiencies, can lead to the development of<unk> .
The most common causes of<unk>  include:
Aphthous<unk> 
Dentures
Folate deficiency
Herpes
Oropharyngeal candidiasis
Vitamin B12 deficiency
Chemotherapy<unk>  should be differentiated from various subtypes of<unk> , as well as from many other disease that can involve the oral cavity, such as agranulocystosis, Behcet's disease, immunodeficiency, and tumors of the oral cavity (e.g., leukoplakia).
The epidemiology and demographics vary among different kinds of<unk> .
Herpetic gingivostomatitis commonly affects children between 6 months and 5 years of age. It occurs less frequently in other age groups.
Noma or gangrenous<unk>  commonly affects children.
Pyostomatitis vegetans commonly affects individuals between the age of 20 and 50 years.
Common risk factors in the development of<unk>  include alcohol, smoking, trauma, stress, nutritional deficiency, and immunocompromised status.
The risk factors believed to influence the development of<unk>  include:
Smoking
Alcohol
Trauma
Psychological stress
H. pylori
Sensitivity to food
Nutritional abnormalities
Immunologic deficiencies (e.g., HIV)
Genetic factors
Chemotherapy or radiotherapy
Poor denture hygiene
According to the the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for<unk> .
If left untreated, herpetic<unk>  resolves after the vesicles erupt and the ulcers heal. The HSV travels along the nerves and moves to the ganglions where it stays in latent form. When the host becomes immunocompromised after taking medications or due to some other illness, the virus assesses the opportunity and through the same nerves becomes active once again manifesting symptoms such as oral vesicles. The viral shedding can continue for 2-12 days after primary infection.
Some complications of<unk>  include:
Meningoencephalitis
Recurrent skin and mouth infections
Dissemination of the infection
Teeth loss
The prognosis of<unk>  is generally good.
Stomatitis
Gastroenteritis
Colitis
Gastritis
Enteritis
Iritis
Pancreatitis
Peptic ulcer