Calluses are areas of thick, hardened and dead skin. They form to protect your skin and structures under your skin from injury, friction and pressure. They may look yellowish or grayish. They are less sensitive to the touch than surrounding skin and they feel rough. Calluses on the foot generally form on the underside of the big toe, he heel and the ball of the foot. The often form where the foot and the beginning of a toe meet.
Calluses are a toughened area of skin which has become relatively thick and hard in response to repeated irritation, pressure or friction. When you rub them too forceful or frequent, then this will cause blisters rather than allow calluses to form. The repeated contact is required and this is a reason why they are most often found on our feet. This is happening because we are walking too frequent . Calluses are generally not harmful but there are some cases when they lead to other problems such as infection or skin ulceration.
In normal cases calluses will form on any part of the skin which is exposed to friction over a long period of time. People often develop calluses on their middle finger of their hand which is caused by writing with a pen or pencil. Also when you play string instruments like violin or guitar you have increased risk of getting calluses . In this case calluses will develop on the 4 fingers of the hand used in holding the strings down to the fingerboard and sometimes on the fingers of the hand used for strumming or pizzicato. Calluses are very common condition on the fingers of double bass and bass guitar players who use both slapping and pizzicato techniques.  Rock climbers also have this condition almost all of their fingers . There are many activities which can result in the formation of a callus and many people see it as a badge of commitment and experience to the activity.
When there is a compression applied by tightly fitting shoes, there are forming calluses on our feet, particularly on the small toes. Wearing high heels, monkey bars, chopping wood, dancing (especially ballet), BMXing, rowing, weight training, martial arts, hiking, rock climbing , use of a chef’s knife, playing musical instruments, wood carving and construction are activities that are notorious for causing calluses.  These activities are not limited which means there can be lot more activities which will cause you calluses. Tenpin bowlers often are developing calluses on their thumbs and occasionally on their middle fingers because they are bowling frequently. In the most cases calluses are found on the foot because this is the place where most friction and pressure are applied.
Calluses can occur on any part of our bodies as a reaction to moderate and constant “grinding” pressure. This is a natural reaction to plantar or palmar skin. When too much friction is occurring too fast for the skin, then it is developing a protective callus which will cause you an abrasion or blister instead. When we want to define this term “callus” in biological way, then we can say that callus are formed by the accumulation of terminally undifferentiated keratinocytes in the outermost layer of our skins. Though the cells of calluses are dead but they are quite resistant to chemical and mechanical insults due to extensive networks of cross – linked proteins and hydrophobic keratin intermediate filaments containing many disulfide bounds.
Calluses are usually forming on knuckles, palms of the hands and feet (usually around the heel area on the skin under the ball of the foot). If you have noticed callus on your body, then you should talk with your doctor as soon as possible because he or she will tell you which is the best natural cure or medicine for you. You should treat the calluses yourself after a podiatrist has identified the cause and advised you about the treatment. Your podiatrist may be able to treat the callused area using a sharp blade to remove the thickened area of the skin. This is usually painless treatment and it can help you to reduce the discomfort and pain.
Other possible causes of calluses include:
- Regularly holding objects such as racquet or hammer 
- Reduced fatty padding – elderly people have less fatty tissue in their skin
- Dry skin 
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