There are different types of corns. Hard corns, soft corns, seed corns, vascular corns and jolly green giant sweet corns !!! Corns are caused by intermittent pressure or focussed areas of pressure, usually over a bony prominence – footwear can be the cause of the pressure that leads to corns.
Corns are a normal reaction to excessive stresses on the skin. When areas of skin are experiencing recurring friction or pressure, thick layers of dead skin cells accumulate and develop the hardened areas we call corns. The hardened dead skin forms a nucleus, usually conical with the apex pointing inwards. The deeper the corn grows, the more likely its pointed end will irritate a nerve if any external pressure is applied to it. Every movement of the live, mobile skin surrounding the nucleus of dead tissue will cause pain, exactly as if a piece of gravel or glass were embedded in the skin. Callus then forms over and around the nucleus in an attempt to isolate the nucleus and protect the site from constant irritation, rubbing and pressure. If this thickening did not form, the epidermis would be eroded away at these frictional/pressure points, exposing the softer more vulnerable under tissues to all the foreign substances and organisms that exist outside the body. A patient with hammertoes would be susceptible to corns on the tops of their toes.
The first and second image shows a hard corn (Heloma Durum), commonly seen on bony prominences.
The third image depicts a soft corn (Heloma Molle) in between the toes, commonly seen between the 4th and 5th toes
As mentioned, there are different forms of corns. The etiology of all true corns is the same, however each corn requires some difference of technique in its treatment and removal. Over the counter corn removers and medicated corn pads contain caustic preparations (salicylic acid) and must be used with care as they can cause severe burns and infection in the normal skin surrounding the corn. Please be aware that these must not be used on patients with diabetes. A corn must not be left untreated as there is a risk of ulceration.