A callus is a thick area of skin that has become tough due to an irritant, pressure, or some form of friction. They are quite common on the feet and appear yellow in color. As calluses thicken they can become painful and may hurt when you walk. Some common causes of foot calluses include:
Wearing new shoes
Foot deformities
Not wearing socks with shoes or sandals
Improper walking motion
Frequently going outside barefoot
Aging
Improper shoe gear
Individuals who experience other issues with their feet are also at higher risk for developing a callus. Those with hammertoe, bunions, and other similar deformities often experience calluses.