Corns can be caused by pressure or friction on the skin, says WebMD. They are usually the result of poor fitting shoes and dissipate with proper footwear.
Corns are not caused by a virus and are not contagious, according to WebMD. Pressure on feet causes skin to die and regrow as a harder protective surface. Soft corns form when this occurs along with sweat becoming trapped where the corn develops.
Corns may look hard, dry, thick and may appear gray or yellow, says WebMD. They can be less sensitive than surrounding skin and feel bumpy. Hard corns are firm, thick and may have a soft yellow ring with a gray center. Soft corns look like open sores.
While not directly painful, corns can cause pain and irritation while walking or wearing shoes, reports WebMD. Pressure applied to the corn, like squeezing, can also cause pain.
While most corns disappear gradually, doctors may shave tops of calluses off to reduce thickness, says WebMD. Moleskin pads that are properly positioned can alleviate pressure on a corn. Most doctors discourage the use of salicylic acid corn remedies, as they can create chemical skin burns around the corn. These burns can cause infections and ulcers for patients with diabetes, poor circulation or numbness in their feet. Oral antibiotics can be used, but pus may have to be removed through an incision.