Updated: Jul 29, 2020
Corn and callus formation are the same process. The term corn is more likely to be used to describe a callus on top of a knuckle of a toe. Callus formation on the feet is generally a normal healthy response of skin that receives too much pressure or friction. The abnormality is the amount of pressure or friction to that area. The skin itself is usually healthy. If the pressure or friction is removed, the callus will usually go away completely. If the pressure or friction returns, the callus will return.
Callus formation is not generally due to a disease or skin problem. The problem is the abnormal pressure or friction. Calluses often form over a bony prominence which makes that area more vulnerable to abnormal pressure or friction.
Calluses on top of the toes or foot are generally from ill-fitting shoes that are pressing on boney prominences. Calluses on the sole of the foot or weight bearing portions of the toes are from excessive pressure or friction of that spot against the floor.
Callus formation is a healthy protective mechanism of the skin similar to the protective process of a sun tan. In both cases, the skin changes to protect itself from the potentially damaging stimulus. A sun tan goes away when you have been out of the sun and the protection is no longer needed. Calluses also go away when the causative pressure or friction is eliminated or significantly reduced. If the damaging stimulus returns, the suntan or callus will return.
Just like the skin of different individuals responds differently to tanning, different skin responds differently to callus formation. Some skin just genetically forms callus more or less easily. This factor cannot be changed, but the external pressure or friction can be changed.
Get rid of the pressure or friction, and you get rid of the corn or callus. If the pressure or friction returns, so does the corn or callus.