The two major factors that are the cause of corns and calluses are friction and pressure. Any condition that causes repetitive friction or pressure will ultimately lead to these skin lesions.
Causative factors include:
Tight and constrictive shoes: This is the most common causes of corns. Shoes that are ill fitting or too tight always compress the toes and lead to calluses. When the shoes are too loose, they will allow the toes to constantly rub against each other and induce friction. Further the toes may also rub against the surface of the inner shoe or the shoe seams and lead to calluses. Women who constantly wear high heel shoes with narrow pointed toes are most prone to corns and calluses.
Bare feet: Wearing shoes and sandals without socks often leads to friction on the sides of the feet, especially the toes. The same thing occurs when the socks worn are loose. In such cases, there are numerous friction burns which are extremely painful
Work related: Repetitive work with hands such as electrical work, hammering, etc can often lead to development of calluses on the hands. This is most likely due to the constant pressure and rubbing of the skin against the hard surface.
Exercise: Individuals who are into sports often exert repetitive pressure and friction on their feet and toes. These individuals usually develop calluses over times.
Abnormal anatomy: Sometimes deformity of the foot also leads to more pressure on one particular side and this often leads to corns.
Lack of protection: Manual laborers, who work without proper gloves or shoes, often develop calluses. The excessive friction from the daily work causes the development of rough scaly skin
Bunions: Bunions have abnormal bony prominences which often lead to excessive pressure on the skin below the bone
Hammertoes: When one of the tendons in the toes is dysfunctional, hammer toes can develop. This leads to pressure along the toe lines and development of corns.
When corns are calluses occur, these are not life threatening. If there are no symptoms, then the best treatment is to avoid the causes.
Individuals who have diabetes or peripheral vascular disease may have compromised blood flow to the foot. These individuals have to be careful because an open skin lesion can rapidly lead to limb threatening infection.
Diabetics should never let anyone touch their feet without first assessing the blood supply to the foot.
The diagnosis of corns or calluses is straightforward. In most cases, a simple physical examination is diagnostic. In rare cases, an x ray of the foot may confirm the cause such as a bunion or hammer toe