Callus
Encyclopedia
A callus is an especially 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 blister
s 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
.
of their dominant hand due to writing with a pen or pencil. Another cause is from playing string instruments like the violin or the guitar; calluses will develop on the four left hand fingers used in holding the strings down to the fingerboard, and sometimes right hand fingers used for pizzicato
or strumming. Calluses are also very common on the fingers of bassists who use both the pizzicato
and slapping
techniques. There are many activities that can result in the formation of a callus, and having one is sometimes viewed as a badge of honor. Activities that are notorious for causing calluses include (but are not limited to) playing musical instruments, martial arts, many sports (specifically racket sports), weight training
, dancing (especially ballet), digging, chopping wood, and wearing high heels. Tenpin bowlers will often develop calluses on their thumbs and occasionally their middle fingers from frequent bowling. Although often found on the foot
(where the most pressure and friction are applied), calluses can occur anywhere on the body as a reaction to moderate, constant "grinding" pressure. It is the natural reaction of the palmar
or plantar skin. Too much friction occurring too fast for the skin to develop a protective callus will cause a blister
or abrasion instead.
Biologically, calluses are formed by the accumulation of terminally
differentiated keratinocyte
s in the outermost layer of skin. Though the cells of calluses are dead, they are quite resistant to mechanical and chemical insults due to extensive networks of cross-linked proteins and hydrophobic
keratin intermediate filaments containing many disulfide bonds.
Sometimes a callus occurs where there is no rubbing or pressure. These hyperkeratoses can have a variety of causes. Some toxins, such as arsenic
, can cause thick palms and soles. Some diseases, such as syphilis
, can cause thickening of the palms and soles as well as pinpoint hyperkeratoses. There is a benign condition called keratosis palmaris et plantaris, which produces corns in the creases of the fingers and non-weight bearing spaces of the feet. Some of this may be caused by actinic keratosis
, which occurs due to overexposure to sun or with age and hormonal shifts.
(or clavus, plural clavi) is a specially-shaped callus of dead skin that usually occurs on thin or glabrous (hairless and smooth) skin surfaces, especially on the dorsal surface of toes or fingers. They can sometimes occur on the thicker palmar
or plantar skin surfaces. Corns form when the pressure point against the skin traces an elliptical or semi-elliptical path during the rubbing motion, the center of which is at the point of pressure, gradually widening. If there is constant stimulation of the tissue producing the corns, even after the corn is surgically removed, the skin may continue to grow as a corn.
The hard part at the center of the corn resembles a funnel with a broad raised top and a pointed bottom. Because of their shape, corns intensify the pressure at the tip and can cause deep tissue damage and ulceration. The scientific name for a corn is heloma (plural helomata). A hard corn is called a heloma durum, while a soft corn is called a heloma molle.
The location of soft corns tends to differ from that of hard corns. Hard corns occur on dry, flat surfaces of skin. Soft corns (frequently found between adjacent toes) stay moist, keeping the surrounding skin soft. The corn's center is not soft however, but indurated.
The specific diagnostic workup and treatments for corns may differ substantially from other forms of calluses
agents containing salicylic acid
, sanded down with a pumice
stone or filed down with a callus shaver, or pared down by a professional such as a podiatrist or a foot health practitioner
.
Before 1937 (when commerce in medicinal cannabis
was effectively banned by a federal law in the United States), topical corn remedies usually contained tincture of cannabis, whose antibacterial properties were an effective agent. In addition, the inclusion of cannabis provided the herbal green appearance expected by consumers of the day.
, this may be an early signs of individuals at an increased risk for foot ulcers.
The stiffness of a callus or corn, coupled with the shear
and pressure that caused it, may tear the capillaries or adjoining tissue, causing bleeding within the callus or corn. Often, bleeding within a callus is an early sign of diabetes, even before elevated blood sugars may be noticed. Although the bleeding can be small, sometimes small pools of blood or hematoma
are formed. The blood itself is an irritant, a foreign body within the callus that makes the area burn or itch. If the pool of blood is exposed to the outside, infection
may follow. Infection may also lead to ulceration. Luckily, this process can be prevented at several places, Diabetic foot infections are the leading cause of diabetic limb amputation
.
, the term is also used to describe a condition of thickened surfaces of leaves or other plant parts. A callus also can refer to an undifferentiated plant cell mass grown on a culture medium, which can be put into a bioreactor
to produce genetically identical cells.
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
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 blister
Blister
A blister is a small pocket of fluid within the upper layers of the skin, typically caused by forceful rubbing , burning, freezing, chemical exposure or infection. Most blisters are filled with a clear fluid called serum or plasma...
s 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
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
.
Cause
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 fingerMiddle finger
The middle finger or long finger is the third digit of the human hand, located between the index finger and the ring finger. It is usually the longest finger...
of their dominant hand due to writing with a pen or pencil. Another cause is from playing string instruments like the violin or the guitar; calluses will develop on the four left hand fingers used in holding the strings down to the fingerboard, and sometimes right hand fingers used for pizzicato
Pizzicato
Pizzicato is a playing technique that involves plucking the strings of a string instrument. The exact technique varies somewhat depending on the type of stringed instrument....
or strumming. Calluses are also very common on the fingers of bassists who use both the pizzicato
Pizzicato
Pizzicato is a playing technique that involves plucking the strings of a string instrument. The exact technique varies somewhat depending on the type of stringed instrument....
and slapping
Slapping
In music, the term slapping is often used to refer to two different playing techniques used on the double bass and on the bass guitar.-Double bass:...
techniques. There are many activities that can result in the formation of a callus, and having one is sometimes viewed as a badge of honor. Activities that are notorious for causing calluses include (but are not limited to) playing musical instruments, martial arts, many sports (specifically racket sports), weight training
Weight training
Weight training is a common type of strength training for developing the strength and size of skeletal muscles. It uses the weight force of gravity to oppose the force generated by muscle through concentric or eccentric contraction...
, dancing (especially ballet), digging, chopping wood, and wearing high heels. Tenpin bowlers will often develop calluses on their thumbs and occasionally their middle fingers from frequent bowling. Although often found on the foot
Foot
The foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws...
(where the most pressure and friction are applied), calluses can occur anywhere on the body as a reaction to moderate, constant "grinding" pressure. It is the natural reaction of the palmar
Palmar
Palmar may refer to:* a directional anatomical term of location* El Palmar de Troya, a small village near Utrera, in Andalusia, Spain* Palmar Sur , a town the Osa region, Puntarenas province, Costa Rica...
or plantar skin. Too much friction occurring too fast for the skin to develop a protective callus will cause a blister
Blister
A blister is a small pocket of fluid within the upper layers of the skin, typically caused by forceful rubbing , burning, freezing, chemical exposure or infection. Most blisters are filled with a clear fluid called serum or plasma...
or abrasion instead.
Biologically, calluses are formed by the accumulation of terminally
Cellular differentiation
In developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation occurs numerous times during the development of a multicellular organism as the organism changes from a simple zygote to a complex system of...
differentiated keratinocyte
Keratinocyte
Keratinocytes are the predominant cell type in the epidermis, the outermost layer of the human skin, constituting 95% of the cells found there. Those keratinocytes found in the basal layer of the skin are sometimes referred to as "basal cells" or "basal keratinocytes"...
s in the outermost layer of skin. Though the cells of calluses are dead, they are quite resistant to mechanical and chemical insults due to extensive networks of cross-linked proteins and hydrophobic
Hydrophobe
In chemistry, hydrophobicity is the physical property of a molecule that is repelled from a mass of water....
keratin intermediate filaments containing many disulfide bonds.
Sometimes a callus occurs where there is no rubbing or pressure. These hyperkeratoses can have a variety of causes. Some toxins, such as arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
, can cause thick palms and soles. Some diseases, such as syphilis
Syphilis
Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...
, can cause thickening of the palms and soles as well as pinpoint hyperkeratoses. There is a benign condition called keratosis palmaris et plantaris, which produces corns in the creases of the fingers and non-weight bearing spaces of the feet. Some of this may be caused by actinic keratosis
Actinic keratosis
Actinic keratosis is a premalignant condition of thick, scaly, or crusty patches of skin. It is more common in fair-skinned people. It is associated with those who are frequently exposed to the sun, as it is usually accompanied by solar damage...
, which occurs due to overexposure to sun or with age and hormonal shifts.
Corns
A cornCorn (medicine)
A corn is a specially shaped callus of dead skin that usually occurs on thin or glabrous skin surfaces, especially on the dorsal surface of toes or fingers. They can sometimes occur on the thicker palmar or plantar skin surfaces...
(or clavus, plural clavi) is a specially-shaped callus of dead skin that usually occurs on thin or glabrous (hairless and smooth) skin surfaces, especially on the dorsal surface of toes or fingers. They can sometimes occur on the thicker palmar
Palmar
Palmar may refer to:* a directional anatomical term of location* El Palmar de Troya, a small village near Utrera, in Andalusia, Spain* Palmar Sur , a town the Osa region, Puntarenas province, Costa Rica...
or plantar skin surfaces. Corns form when the pressure point against the skin traces an elliptical or semi-elliptical path during the rubbing motion, the center of which is at the point of pressure, gradually widening. If there is constant stimulation of the tissue producing the corns, even after the corn is surgically removed, the skin may continue to grow as a corn.
The hard part at the center of the corn resembles a funnel with a broad raised top and a pointed bottom. Because of their shape, corns intensify the pressure at the tip and can cause deep tissue damage and ulceration. The scientific name for a corn is heloma (plural helomata). A hard corn is called a heloma durum, while a soft corn is called a heloma molle.
The location of soft corns tends to differ from that of hard corns. Hard corns occur on dry, flat surfaces of skin. Soft corns (frequently found between adjacent toes) stay moist, keeping the surrounding skin soft. The corn's center is not soft however, but indurated.
The specific diagnostic workup and treatments for corns may differ substantially from other forms of calluses
Prevention
Corns and calluses are easier to prevent than to treat. When it is not desirable to form a callus, minimizing rubbing and pressure will prevent callus formation. Footwear should be properly fitted, gloves may be worn, and protective pads, rings or skin dressings may be used. People with poor circulation or sensation should check their skin often for signs of rubbing and irritation so they can minimize any damage.Treatment
Calluses and corns may go away by themselves eventually, once the irritation is consistently avoided. They may also be dissolved with keratolyticKeratolytic
Keratolytic therapy is treatment to remove warts and other lesions in which the epidermis produces excess skin. In this therapy, acid medicine, such as salicylic acid is put on the lesion. Keratolytic therapy thins the skin on and around the lesion. It causes the outer layer of the skin to loosen...
agents containing salicylic acid
Salicylic acid
Salicylic acid is a monohydroxybenzoic acid, a type of phenolic acid and a beta hydroxy acid. This colorless crystalline organic acid is widely used in organic synthesis and functions as a plant hormone. It is derived from the metabolism of salicin...
, sanded down with a pumice
Pumice
Pumice is a textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the simultaneous actions of rapid...
stone or filed down with a callus shaver, or pared down by a professional such as a podiatrist or a foot health practitioner
Foot health practitioner
A Foot Health Practitioner is a provider of routine foot care working in the private sector. The title is most used in the United Kingdom and the Republic of Ireland. FHPs undertake training to recognise, assess and treat foot conditions....
.
Before 1937 (when commerce in medicinal cannabis
Cannabis
Cannabis is a genus of flowering plants that includes three putative species, Cannabis sativa, Cannabis indica, and Cannabis ruderalis. These three taxa are indigenous to Central Asia, and South Asia. Cannabis has long been used for fibre , for seed and seed oils, for medicinal purposes, and as a...
was effectively banned by a federal law in the United States), topical corn remedies usually contained tincture of cannabis, whose antibacterial properties were an effective agent. In addition, the inclusion of cannabis provided the herbal green appearance expected by consumers of the day.
Diabetes
People with diabetes face special skin challenges. Because diabetes affects the capillaries, the small blood vessels which feed the skin, thickening of the skin with callus increases the difficulty of supplying nutrients to the skin. Callus formation is seen in high numbers of patients with diabetes and together with absent foot pulses and formation of hammer toeHammer toe
A hammer toe or contracted toe is a deformity of the proximal interphalangeal joint of the second, third, or fourth toe causing it to be permanently bent, resembling a hammer...
, this may be an early signs of individuals at an increased risk for foot ulcers.
The stiffness of a callus or corn, coupled with the shear
Shear stress
A shear stress, denoted \tau\, , is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section...
and pressure that caused it, may tear the capillaries or adjoining tissue, causing bleeding within the callus or corn. Often, bleeding within a callus is an early sign of diabetes, even before elevated blood sugars may be noticed. Although the bleeding can be small, sometimes small pools of blood or hematoma
Hematoma
A hematoma, or haematoma, is a localized collection of blood outside the blood vessels, usually in liquid form within the tissue. This distinguishes it from an ecchymosis, which is the spread of blood under the skin in a thin layer, commonly called a bruise...
are formed. The blood itself is an irritant, a foreign body within the callus that makes the area burn or itch. If the pool of blood is exposed to the outside, infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
may follow. Infection may also lead to ulceration. Luckily, this process can be prevented at several places, Diabetic foot infections are the leading cause of diabetic limb amputation
Amputation
Amputation is the removal of a body extremity by trauma, prolonged constriction, or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is carried out on individuals as a preventative surgery for...
.
Other meanings
In botanyBotany
Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...
, the term is also used to describe a condition of thickened surfaces of leaves or other plant parts. A callus also can refer to an undifferentiated plant cell mass grown on a culture medium, which can be put into a bioreactor
Bioreactor
A bioreactor may refer to any manufactured or engineered device or system that supports a biologically active environment. In one case, a bioreactor is a vessel in which a chemical process is carried out which involves organisms or biochemically active substances derived from such organisms. This...
to produce genetically identical cells.
See also
- HyperkeratosisHyperkeratosisHyperkeratosis is thickening of the stratum corneum, often associated with a qualitative abnormality of the keratin, and also usually accompanied by an increase also in the granular layer...
- CallosityCallosityA callosity is another name for callus, a piece of skin that has become thickened as a result of repeated contact and friction.- Monkeys :When occurring on an animal's buttocks, as with baboons, they are specifically called ischial callosities...
- CatagmaticCatagmaticIn pre-modern medicine, the term catagmatic generally referred to any treatment purported to heal bone fractures, by promoting the formation of a callus. The principal catagmatics were Armenian bole, gum tragacanth, osteocolla, Cyprus nuts, frankincense, aloes, and acacia. The word comes from the...
- ZebibahZebibahA zebibah is a darkened area of callused skin on the forehead. Muslims sometimes acquire one from pressing the head to the ground during daily prayers...
- List of cutaneous conditions