<unk>  is thought to be multifactorial disorder of infectious origin, with many local and systemic predisposing factors. The sores in<unk>  are often infected with fungi (yeasts), bacteria, or a combination thereof; this may represent a secondary, opportunistic infection by these pathogens. Some studies have linked the initial onset of<unk>  with nutritional deficiencies, especially of the B (B2-riboflavin) vitamin and iron (which causes iron deficiency anemia), which in turn may be evidence of malnutrition or malabsorption.<unk>  can be a manifestation of contact dermatitis, which is considered in two groups; irritational and allergic. Infection The involved organisms are: * Candida species alone (usually Candida albicans), which accounts for about 20% of cases, * Bacterial species, either: * Staphylococcus aureus alone, which accounts for about 20% of cases, * β-hemolytic streptococci alone. These types of bacteria have been detected in between 8–15% of cases of<unk> , but less commonly are they present in isolation, * Or a combination of the above organisms, (a polymicrobial infection) with about 60% of cases involving both C. albicans and S. aureus. Candida can be detected in 93% of<unk>  lesions. This organism is found in the mouths of about 40% of healthy individuals, and it is considered by some to be normal commensal component of the oral microbiota. However, Candida shows dimorphism, namely a yeast form which is thought to be relatively harmless and a pathogenic hyphal form which is associated with invasion of host tissues. Potassium hydroxide preparation is recommended by some to help distinguish between the harmless and the pathogenic forms, and thereby highlight which cases of<unk>  are truly caused by Candida. The mouth may act as a reservoir of Candida that reinfects the sores at the corners of the mouth and prevents the sores from healing. A lesion caused by recurrence of a latent herpes simplex infection can occur in the corner of the mouth. This is herpes labialis (a cold sore), and is sometimes termed<unk>  herpes simplex". A cold sore at the corner of the mouth behaves similarly to elsewhere on the lips, and follows a pattern of vesicle (blister) formation followed by rupture leaving a crusted sore which resolves in about 7–10 days, and recurs in the same spot periodically, especially during periods of stress. Rather than utilizing antifungal creams,<unk>  herpes simplex is treated in the same way as a cold sore, with topical antiviral drugs such as aciclovir. Irritation contact dermatitis A famous sketch by Leonardo da Vinci in preparation to depict the face of Judas Iscariot in The Last Supper. The subject shows overclosure of the jaws and loss of facial support around the mouth. Pronounced skin folds extending from the corner of the mouth. 22% of cases of<unk>  are due to irritants. Saliva contains digestive enzymes, which may have a degree of digestive action on tissues if they are left in contact. The corner of the mouth is normally exposed to saliva more than any other part of the lips. Reduced lower facial height (vertical dimension or facial support) is usually caused by edentulism (tooth loss), or wearing worn down, old dentures or ones which are not designed optimally. This results in overclosure of the mandible (collapse of the jaws), which extenuates the<unk>  skin folds at the corners of the mouth, in effect creating an intertriginous skin crease. The tendency of saliva to pool in these areas is increased, constantly wetting the area, which may cause tissue maceration and favors the development of a yeast infection. As such,<unk>  is more commonly seen in edentulous people (people without any teeth). It is by contrast uncommon in persons who retain their natural teeth.<unk>  is also commonly seen in denture wearers.<unk>  is present in about 30% of people with denture-related stomatitis. It is thought that reduced vertical dimension of the lower face may be a contributing factor in up to 11% of elderly persons with<unk>  and in up to 18% of denture wearers who have<unk> . Reduced vertical dimension can also be caused by tooth migration, wearing orthodontic appliances, and elastic tissue damage caused by ultraviolet light exposure and smoking. Habits or conditions that keep the corners of the mouth moist might include chronic lip licking, thumb sucking (or sucking on other objects such as pens, pipes, lollipops), dental cleaning (e.g. flossing), chewing gum, hypersalivation, drooling and mouth breathing. Some consider habitual lip licking or picking to be a form of nervous tic, and do not consider this to be true<unk> , instead calling it perlèche (derived from the French word pourlècher meaning "to lick one’s lips"), or "factitious cheilitis" is applied to this habit. The term "cheilocandidiasis" describes exfoliative (flaking) lesions of the lips and the skin around the lips, and is caused by a superficial candidal infection due to chronic lip licking. Less severe cases occur during cold, dry weather, and is a form of chapped lips. Individuals may lick their lips in an attempt to provide a temporary moment of relief, only serving to worsen the condition. The sunscreen in some types of lip balm degrades over time into an irritant. Using expired lipbalm can initiate mild<unk> , and when the person applies more lipbalm to alleviate the cracking, it only aggravates it. Because of the delayed onset of contact dermatitis and the recovery period lasting days to weeks, people typically do not make the connection between the causative agent and the symptoms. Nutritional deficiencies Several different nutritional deficiency states of vitamins or minerals have been linked to AC. It is thought that in about 25% of people with AC, iron deficiency or deficiency of B vitamins are involved. Nutritional deficiencies may be a more common cause of AC in Third World countries. Chronic iron deficiency may also cause koilonychia (spoon shaped deformity of the fingernails) and glossitis (inflammation of the tongue). It is not completely understood how iron deficiency causes AC, but it is known that it causes a degree of immunocompromise (decreased efficiency of the immune system) which may in turn allow an opportunistic infection of candida. Vitamin B2 deficiency (ariboflavinosis) may also cause AC, and other conditions such as redness of mucous membranes, magenta colored glossitis (pink inflammation of the tongue). Vitamin B5 deficiency may also cause AC, along with glossitis, and skin changes similar to seborrhoeic dermatitis around the eyes, nose and mouth. Vitamin B12 deficiency is sometimes responsible for AC, and commonly occurs together with folate deficiency (a lack of folic acid), which also causes glossitis and megaloblastic anemia. Vitamin B3 deficiency (pellagra) is another possible cause, and in which other association conditions such as dermatitis, diarrhea, dementia and glossitis can occur. Biotin (vitamin B7) deficiency has also been reported to cause AC, along with hair loss (alopecia) and dry eyes. Zinc deficiency is known to cause AC. Other symptoms may include diarrhea, alopecia and dermatitis. Acrodermatitis enteropathica is an autosomal recessive genetic disorder causing impaired absorption of zinc, and is associated with AC. In general, these nutritional disorders may be caused by malnutrition, such as may occur in alcoholism or in poorly considered diets, or by malabsorption secondary to gastrointestinal disorders (e.g. Coeliac disease or chronic pancreatitis) or gastrointestinal surgeries (e.g. pernicious anemia caused by ileal resection in Crohn's disease). Systemic disorders Some systemic disorders are involved in<unk>  by virtue of their association with malabsorption and the creation of nutritional deficiencies described above. Such examples include people with anorexia nervosa. Other disorders may cause lip enlargement (e.g. orofacial granulomatosis), which alters the local anatomy and extenuates the skin folds at the corners of the mouth. More still may be involved because they affect the immune system, allowing normally harmless organisms like Candida to become pathogenic and cause an infection. Xerostomia (dry mouth) is thought to account for about 5% of cases of AC. Xerostomia itself has many possible causes, but commonly the cause may be side effects of medications, or conditions such as Sjögren's syndrome. Conversely, conditions which cause drooling or sialorrhoea (excessive salivation) can cause<unk>  by creating a constant wet environment in the corners of the mouth. About 25% of people with Down syndrome appear to have AC. This is due to relative macroglossia, an apparently large tongue in a small mouth, which may constantly stick out of the mouth causing maceration of the corners of the mouth with saliva. Inflammatory bowel diseases (such as Crohn's disease or ulcerative colitis) can be associated with<unk> . In Crohn's, it is likely the result of malabsorption and immunosuppressive therapy which gives rise to the sores at the corner of the mouth. Glucagonomas are rare pancreatic endocrine tumors which secrete glucagon, and cause a syndrome of dermatitis, glucose intolerance, weight loss and anemia. AC is a common feature of glucagonoma syndrome. Infrequently,<unk>  may be one of the manifestations of chronic mucocutaneous candidiasis, and sometimes cases of oropharyngeal or esophageal candidiasis may
Angular cheilitis
Actinic cheilitis
Capillaritis
Conjunctivochalasis
Blepharochalasis
Vulvitis
Cuffitis
Symblepharon