Corns are patches of thickened skin, often found on the soles of the feet or toes. They are normally painless to start with. These areas form to protect the skin and stop the body from developing blisters. Corns can be caused by bunions, hammer toe, or ill-fitting shoes. Over time, they may become painful and should be treated. Corn plasters are available over the counter (OTC); they relieve pressure on the corn and allow it time to heal. In some cases, a doctor may recommend surgical removal.