Picture of Corns and Calluses
Corns: Corns generally occur on the tops and sides of the toes. A hard corn is a small patch of thickened, dead skin with a packed center. A soft corn has a much thinner surface and usually occurs between the 4th and 5th toes. A seed corn is a tiny, discrete callous that can be very tender if it's on a weight-bearing part of the foot. Seed corns tend to occur on the bottom of the feet, and some doctors believe this condition is caused by plugged sweat ducts.
Calluses: Calluses can develop on hands, feet, or anywhere there is repeated friction -- even on a violinist's chin. Like corns, calluses have several variants. The common callus usually occurs when there's been a lot of rubbing against the hands or feet. A plantar callus is found on the bottom of the foot.
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Text: "Understanding Corns and Calluses - the Basics", WebMD Medical Reference