Corns, also called helomas, are thickened areas of skin that form in response to excessive pressure and friction. They form to protect the skin and the structures beneath it from damage or injury. Corns are usually hard and circular, with a waxy or translucent center. They may become painful or ulcerated in response to persistent friction.
There are two types of corns. Hard corns (heloma durums) are the most common type. They are caused primarily by ill-fitting shoes and toe deformities. They usually develop on the tops and tips of the toes and on the sides of the feet. Soft corns (heloma molles) usually occur as the result of bone abnormalities in the toes. They develop between the toes and are sometimes referred to as "kissing corns".