Corns and callus are one of the most common problems seen by Podiatrists. They can occur on any part of the foot and vary in symptoms from a mild callus under the foot, to an infected ulcer that can develop under a corn on a toe.
A corn or callus are areas of thickened skin that occur in areas of pressure. They are actually a normal and natural way for the body to protect itself. For example, callus develops on the hand when chopping a lot of wood - its a normal way for the skin to protect itself. In the foot, the skin will thicken up to protect itself when there are areas of high pressure. The problem occurs when the pressure continues, so the skin gets thicker. It eventually becomes painful and is treated as something foreign by the body.
Pathologically they are all the same - the skin has thickened in response to pressure. A callus generally refers to a more diffuse thickening of the skin (more common on the toes, but can occur under the ball of the foot) whereas a corn is a thicker more focal area area (more common on the toes). A corn can occur under and be surrounded by callus.
Corns and callus are caused by one thing - TOO MUCH PRESSURE, usually in combination with some friction. There is no other way to get them. The pressure stimulates the skin to thicken to protect itself, but as the stimulation of the pressure continues, it becomes painful. Too much pressure can be from footwear that is too tight, or toe deformities, such as hammer toes. The top of the hammer toe is an area for increased pressure on the top of the toe bony prominence
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