Infrequently, angular cheilitis may be one of the manifestations of chronic mucocutaneous candidiasis, and sometimes cases of oropharyngeal or esophageal candidiasis may accompany angular cheilitis. Angular cheilitis may be present in human immunodeficiency virus infection, neutropenia, or diabetes. Angular cheilitis is more common in people with eczema because their skin is more sensitive to irritants. Other conditions possibly associated include plasma cell gingivitis, Melkersson–Rosenthal syndrome, or sideropenic dysphagia (also called Plummer–Vinson syndrome or Paterson–Brown–Kelly syndrome). Drugs
Several drugs may cause AC as a side effect, by various mechanisms, such as creating drug-induced xerostomia. Various examples include isotretinoin, indinavir, and sorafenib. Isotretinoin (Accutane), an analog of vitamin A, is a medication which dries the skin. Less commonly, angular cheilitis is associated with primary hypervitaminosis A, which can occur when large amounts of liver (including cod liver oil and other fish oils) are regularly consumed or as a result from an excess intake of vitamin A in the form of vitamin supplements. Recreational drug users may develop AC. Examples include cocaine, methamphetamine, heroin, and hallucinogens. Allergic contact dermatitis
Allergic reactions may account for about 25–34% of cases of generalized cheilitis (i.e., inflammation not confined to the angles of the mouth). It is unknown how frequently allergic reactions are responsible for cases of angular cheilitis, but any substance capable of causing generalized allergic cheilitis may present involving the corners of the mouth alone.
If there is a nutritional deficiency underlying the condition, various other signs and symptoms such as glossitis (swollen tongue) may be present. In people with angular cheilitis who wear dentures, often there may be erythematous mucosa underneath the denture (normally the upper denture), an appearance consistent with denture-related stomatitis. Typically the lesions give symptoms of soreness, pain, pruritus (itching) or burning or a raw feeling. Causes
Angular cheilitis is thought to be multifactorial disorder of infectious origin, with many local and systemic predisposing factors. The sores in angular cheilitis 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 angular cheilitis 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. Angular cheilitis 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 angular cheilitis, 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 angular cheilitis lesions.