Angular cheilitis is characterized by inflammatory lesions presenting in the corner(s) of the mouth. The causes include infection with Candida albicans or Staphylococcus aureus, wearing oral dentures or other devices, anemia, deficiencies in the B vitamins, etc. The diagnosis is achieved by findings on physical exam, a thorough history, and a workup of underlying etiologies.
Angular cheilitis is defined as inflammation of the corner(s) of the mouth . While the cause has not been completely elucidated , the most predominant etiology is infection with Candida albicans (commonly found on dentures) , Staphylococcus aureus (found on face masks), and beta-hemolytic streptococci   . Specifically, this condition may arise from poorly fitting oral dentures , occupational face masks, pacifier use in young children , contact irritation such as with nickel found in orthodontic braces  , excessive salivation  , and thumb sucking and lip licking . Very importantly, angular cheilitis can develop secondary to anemia and deficiency in the B vitamins as well as immunosuppression . It is also one of the oral manifestations in patients with Crohn's disease and may be observed in those with no gastrointestinal involvement   .
This unpleasant condition is characterized by erythematous, scaly, and ulcerating fissures found on the angles of the mouth . These lesions can bleed and cause pain and burning, especially when applying pressure on them . Additionally, the lips are often dry. Successful therapy is essential to prevent further episodes of angular cheilitis .
The inspection yields findings such as cracking, mucosal atrophy, crusting, ulceration, and other signs suggestive of inflammation . The patient may be wearing dentures or have manifestations of the gingival and dental disease .
The diagnosis is based on clinical findings and assessment of risk factors. Furthermore, the workup consists of the patient's history, physical exam, and investigation of the etiology.
Very importantly, the clinician must inquire about the onset, duration, previous episodes, and past treatments . In an effort to determine the predisposing factors and underlying cause, the clinician should elicit the patient's dental history, use and fit of dentures or other prostheses, dental hygiene, and other pertinent information  . Additional details regarding any medication use, tobacco smoking/chewing, and alcohol use should be obtained  . Moreover, the patient's medical history should be evaluated for anemia, nutritional deficiencies, immunosuppression, allergic cutaneous conditions, and so forth  .
Swabs of the angles of the mouth and nose are helpful with determining the offending organism. Additionally, samples of the dentures are useful for microbial assessment .
If primary therapy is ineffective, the patient should undergo a thorough workup for anemia and nutritional deficiencies with a complete blood count (CBC), iron studies as well as measurements of vitamins B2, B6, B12, and folate  . Correction of iron deficiency anemia and any vitamin insufficiency will successfully treat the angular cheilitis  .
Rose JA. Folic-acid deficiency as a cause of angular cheilosis. Lancet. 1971;2(7722):453–454.