Corns and calluses are skin conditions that occur as the body’s response to friction or pressure against the skin. They are also often the first sign of a bunion, hammer toe or other bony deformity on the foot. Corns can range from a slight thickening of the skin to a painful, hard bump, and often form on top of buckled toe joints (hammer toes).Calluses are commonly a more spread out area of thickened skin, and often occur on the balls of the feet. A bunion is an enlargement of the joint at the base of the big toe (the metatarsal-phalangeal [MTP] joint) that forms when the bone or tissue at the big toe joint moves out of place. This forces the toe to bend toward the others, causing a prominent lump of bone that is often painful.