A callus (or callosity) is a toughened area of skin which has become relatively thick and hard in response to repeated friction, pressure, or other irritation. Rubbing that is too frequent or forceful will cause blisters rather than allow calluses to form. Since repeated contact is required, calluses are most often found on feet because of frequent walking. Calluses are generally not harmful, but may sometimes lead to other problems, such as skin ulceration or infection.

Normally, a callus will form on any part of the skin exposed to friction over a long period of time. For example, people often develop calluses on the middle finger of their dominant hand due to writing with a pen or pencil. Another cause is from playing string instruments like the guitar or the violin; calluses will develop on the four fingers of the hand used in holding the strings down to the fingerboard, and sometimes on the fingers of the hand used for pizzicato or strumming. Calluses are also very common on the fingers of bassists who use both the pizzicato and slapping techniques. This also applies to rock climbers on almost all of their fingers. There are many activities that can result in the formation of a callus, and having one is sometimes viewed as a badge of honor.

It is almost the same principle as a facial peel, using AHA products. If we can have face peels why not have foot peels as well.