corn, in skin disease, horny thickening of the skin on the foot or toes, produced by repeated friction or pressure. Extensive proliferation of the stratum corneum, the horny layer of the epidermis, results in a conical callus with its broad end on the surface and its point directed inward; the dense centre of this cone presses on sensory nerves, causing pain when direct pressure is applied. The corn’s surface is usually hard and shiny, but corns between the toes may be soft and soggy from perspiration.
Corns are treated by applying plasters of salicylic or dichloroacetic acid to the site after the core has been removed and the callus pared. They are likely to recur, however, unless the source of friction or pressure is eliminated by a change in footwear or in walking habits. Long-lasting corns may produce a bony spur that must be removed surgically.