If you have ever shaken hands with a rock climber, guitarist or builder then you might have noticed just how tough their skin is. This can be a painful experience, a bit like grabbing sandpaper. Chances are that you will have figured that their tough skin is down to their regular use of their hands, but what precisely is going on here that makes the skin so tough?
The answer is that they have likely developed calluses which are areas of toughened sin that are thicker and harder than other areas. These develop in response to friction and can develop in any area that is regularly exposed to friction. For most people the most likely area to have calluses is on the toes, which will be the result of rubbing against the inside of the shoe. You might also notice a small lump on the inside of your middle finger, which is caused by repeatedly writing and resting a pen or pencil there.
How Calluses Form
The big question though is how they form, and what precisely is going on biologically.
The answer is that calluses are actually the result of additional layers added to your skin. Normally your skin is made up from a number of different layers made from different types of cell. On the outermost surface are hardened, dead skin cells normally piled in a layer roughly twenty five cells thick. These cells act as a nice 'buffer', meaning that when you scrape your hand or your finger, you simply scrape off dead skin cells rather than the healthy living ones underneath.
When you brush away these cells though, your body recognises they're gone and responds by creating more. If you keep scraping them away, then your body gets used to replenishing them more quickly and assumes that's how quickly you need them. Eventually it begins replacing the skin there more quickly than you can get rid of it and that's what you call a callus.
When a Callus Becomes a Corn
In some cases calluses can grow too much, in which case they can become 'corns'. These are similar thick areas of skin that dig into the soft skin underneath and become painful. These are most common on the feet, and if you have corns then you should see a podiatrist who can use a scalpel to trim them down or a chemical treatment to soften/remove them.