Corns can be annoying, but the body actually forms them to protect sensitive skin.
Corns generally occur on the tops and sides of the foot. A hard corn is a small patch of thickened, dead skin with a central core. 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.
Some corns on the feet develop from an improper walking motion, but most are caused by ill-fitting shoes. High-heeled shoes are the worst offenders. They put pressure on the toes and make women four times as likely as men to have foot problems. Other risk factors include deformities and wearing shoes or sandals without socks, which can lead to friction on the feet.