Title: Angular cheilitis
Content:  the facial skin. Initially, the corners of the mouth develop a gray-white thickening and adjacent erythema (redness). Later, the usual appearance is a roughly triangular area of erythema, edema (swelling) and breakdown of skin at either corner of the mouth. The mucosa of the lip may become fissured (cracked), crusted, ulcerated or atrophied. There is not usually any bleeding. Where the skin is involved, there may be radiating rhagades (linear fissures) from the corner of the mouth. Infrequently, the dermatitis (which may resemble eczema) can extend from the corner of the mouth to the skin of the cheek or chin. If Staphylococcus aureus is involved, the lesion may show golden yellow 
Title: Skin fissure
Content:  A skin area on which there are many skin fissures is called cracked skin, and is most commonly a result of skin dryness. Ichthyosis is a genetic disorder where there is often severe skin cracking.
Title: Angular cheilitis
Content:  22% of cases of angular cheilitis 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 angular skin folds at the corners of the mouth, in effect creating an intertriginous skin crease. The tendency of saliva to pool in these 
Title: Angular cheilitis
Content:  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 "angular 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, angular herpes simplex is treated in the same way as a cold sore, with topical antiviral drugs such as aciclovir.
Title: Angular cheilitis
Content:  Angular cheilitis (AC) is inflammation of one or both corners of the mouth. Often the corners are red with skin breakdown and crusting. It can also be itchy or painful. The condition can last for days to years. Angular cheilitis is a type of cheilitis (inflammation of the lips). Angular cheilitis can be caused by infection, irritation, or allergies. Infections include by fungi such as Candida albicans and bacteria such as Staph. aureus. Irritants include poorly fitting dentures, licking the lips or drooling, mouth breathing resulting in a dry mouth, sun exposure, overclosure of the mouth, smoking, and minor trauma. Allergies may include substances like toothpaste, 
Title: Stomatitis
Content:  Inflammation of the corners (angles) of the lips is termed angular stomatitis or angular cheilitis. In children a frequent cause is repeated lip-licking, and in adults it may be a sign of underlying iron deficiency anemia, or vitamin B deficiencies (e.g., B2-riboflavin, B9-folate, or B12-cobalamin, which in turn may be evidence of poor diets or malnutrition such as celiac disease). Also, angular cheilitis can be caused by a patient's jaws at rest being 'overclosed' due to edentulousness or tooth wear, causing the jaws to come to rest closer together than if the complete/unaffected dentition were present. This causes skin folds around the angle of the mouth which are kept moist by saliva, which in turn favours infection; mostly by Candida albicans or similar species. Treatment usually involves the administration of topical nystatin or similar antifungal agents. Another treatment can be to correct the jaw relationship with dental treatment (e.g., dentures or occlusal adjustment).
Title: Angular cheilitis
Content:  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 angular cheilitis, 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.
Title: Angular cheilitis
Content:  Severe tooth wear or ill fitting dentures may cause wrinkling at the corners of the lip that creates a favorable environment for the condition. This can be corrected with onlays or crowns on the worn teeth to restore height or new dentures with "taller" teeth. The loss of vertical dimension has been associated with angular cheilitis in older individuals with an increase in facial laxity.
Title: Actinic cheilitis
Content:  AC almost always affects the lower lip and only rarely the upper lip, probably because the lower lip is more exposed to the sun. In the unusual cases reported where it affects the upper lip, this may be due to upper lip prominence. The commissures (corners of the mouth) are not usually involved. Affected individuals may experience symptoms such as a dry sensation and cracking of the lips. It is usually painless and persistent. The appearance is variable. White lesions indicate hyperkeratosis. Red, erosive or ulcerative lesions indicate atrophy, loss of epithelium and inflammation. Early, acute lesions may be erythematous (red) and edematous (swollen). With months and years of sun exposure, the lesion becomes chronic and may be 
Title: Cheilitis
Content:  Chapped lips (also known as cheilitis simplex or common cheilitis ) are characterized by cracking of the lips. The lower lip usually becomes inflamed. There may also be burning or the formation of large, painful cracks when the lips are stretched. Chronic cheilitis simplex can progress to crusting and bleeding. Counterintuitively, constant licking of the lips causes drying and irritation, and eventually the mucosa splits or cracks. The lips have a greater tendency to dry out in cold, dry weather. Digestive enzymes present in the saliva may also irritate the lips, and the evaporation of the water in saliva saps moisture from them. Some children have a habit of sucking and chewing on the lower lip, producing a combination of cheilitis and a sharply demarcated perioral erythema. Treatment is usually successful with the use of topical medications. Medical grade (USP) lanolin accelerates the repair of the lips. Sometimes the term "cheilitis simplex" is used interchangeably with cheilitis in general; however, exfoliative cheilitis is also sometimes stated to be the equivalent of chapped lips.

Question: what causes cracked skin at the corners of your mouth?
Answer: allergies.
infection.
irritation.