The hard truth about calluses.

• Position: Podiatry

Calluses on the feet are not attractive, but there are things to be learned from them. According to Lee S. Cohen, a Philadelphia-area podiatrist and foot and ankle surgeon, calluses act as a "map" to pinpoint a variety of foot and ankle problems as well as issues with footwear.

"Calluses are your body's natural defense mechanism against friction," Cohen points out. "So, if you find that you tend to have heavily-callused feet or keep developing a callus in a specific area, it is probably because you are wearing the wrong type of shoes or there is a functional issue with the way you walk that might need to be addressed."

Most calluses do not pose serious health issues and can be handled at home with methods such as creams and effective tools (like foot files). Some calluses, however, do require medical attention. So, how do you separate the merely unsightly from the seriously unhealthy? Cohen offers these insights:

What causes calluses on the heels? "The callused heel is a doctor's nemesis because it is not easy to treat. It is usually a result of the combined effect of dry skin and constant irritation that may be caused by a particular shoe or type of shoe. Mules, slides, and sandals are often the culprit. Poor foot mechanics or weight can also be part of the problem."

What can you do? Stay away from open-backed shoes. Choose footwear that provides heel support on all sides. Buy socks with double-thick heels.

When should you call a podiatrist? "If heel calluses become so hard and dry they crack, the result is called a fissure or lesion of the skin, and the area may bleed and become infected. If the skin is open or bleeding, you should make it a priority to see a doctor."

What causes calluses on the balls of the feet? "[They] are called plantar calluses and they develop from pressure of an out-of-position bone, usually the metatarsal." The metatarsals are in the middle of the front of the foot, which connect to the toes. They should be parallel to the floor but, if the ligaments around them loosen, these bones may drop and hit the ground. As a result, the skin under these bones thickens like...