Randy Jacobs, M.D. Patient Education

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Corns and Calluses




Calluses can be advantageous to some but painful to others, while corns are characteristically painful to all. Gentle paring with a scalpel can differentiate corns and calluses, which may be confused with plantar warts. If the abnormality is a wart, this will reveal soft, granular, elongated mounds of dermis projecting up into the epidermis. Treatment of corns and calluses includes relieving the cause of pressure or friction. Properly fitting shoes and corn/callus pads can help prevent or minimize these common skin disorders. Friction is essential in daily activities such as gripping, standing, and moving. However, a variety of skin changes can result from chronic exposure of the skin to friction, pressure, shearing or abrasion. Corns and calluses, two such skin changes, occur mainly on the hands, feet, knees, and elbows, and sometimes even on the lips and neck. At work as well as in sports, skin changes due to this trauma are often regarded as a badge or sign of the individual's craft or trade. The Health and Nutrition Examination Survey places the incidence of corns and calluses at 156.9 per 1,000 people, with only 3.2 requiring medical attention. According to the Health Interview Survey, the prevalence was higher with increasing age and among females and nonwhite. The survey also reported an inverse relationship between prevalence and family income. Following is a discussion of corns and calluses, their causes, treatment, and prevention.



A corn is a circumscribed, conical, hyperkeratotic thickening of the stratum corneum, the horny, most superficial layer of the skin. The base of the corn is on the cutaneous surface; the apex points inward, pressing against subjacent structures such as bony prominences. A semiopaque area by hyperkeratosis surrounds the surface of the hard core of the corn, and the adjacent skin may be red and scaly. There are two varieties of corns: hard corns, which develop on the exposed surfaces of the feet and toes; and soft corns, which occur between the toes and are softened by sweat. The surface of the hard corn is shiny and polished; its horny core is in the densest part of the lesion, visible when the upper layers are shaved off. Direct pressure on the core evokes dull, penetrating, or exquisite stabbing pain through pressure on the underlying sensory nerves of the papillary layer of the dermis. This pain is often worse when the humidity is high. The soft corn usually occurs in the fourth interdigital space and is associated with an exostosis (a bony growth that protrudes from the normal bone structure). It appears white because of maceration. Both hard and soft corns may develop a sinus tract that communicates with the underlying bursa. Sinus tract formation and bacterial invasion are more likely to occur with soft corns because of the tissue maceration. Persons with diabetes mellitus or arteriosclerosis may be especially predisposed to sinus tract formation. Hemorrhagic corns may also develop, especially in persons with diabetes.



A callus is a diffuse thickening of the stratum corneum (the uppermost layer of the skin). It is a circumscribed, non-penetrating plaque of hyperkeratosis induced by pressure, repeated friction, or shearing trauma. True calluses lack a hard central core, which is the characteristic of a corn. The diffuse thickening tends to occur at areas that naturally have a thick horny layer and are subjected to intermittent pressure. Commonly affected areas include the soles and palms, over the bony prominences of the joints.


Differentiation from warts

Plantar corns and calluses may be confused with plantar warts. A wart may appear as a small, raised bump with a rough surface and clearly defined borders. It is usually the same color as the surrounding skin but sometimes is darker. Warts tend to be endophytic (growing inward) when they are located on a weight-bearing surface. However, a wart may appear clinically identical to a simple corn or callus. Plantar warts, like corns, are often painful with walking and may look like simple hyperkeratosis. Differentiating these warts from calluses can be aided by gentle paring with a scalpel, which reveals the soft, granular, elongated dermal papillae (mounds of dermis that project up into the epidermis) of a wart. In addition, warts often display the fine black dots (bleeding points) of thrombosed capillaries within a defined margin of white or brownish tissue; the skin markings characteristically are obliterated. In contrast, calluses have clear horny tissue; they have no nucleus, and the normal skin marking are preserved. (When the horny core of a corn is removed, the normal skin markings are visible through the lesion). Pressing the affected site may help differentiate a corn or callus from a wart. This simple clinical test assumes that corns and calluses are more painful with direct pressure than with pinching and that the reverse is true of warts






The hyperkeratotic response of calluses is thought to be a protective mechanism from pressure and friction. In a review of the abnormal biomechanics of feet, experts Gibbs and Boxer suggest that osteoarthritis, tight shoes, and an abnormal gait are all likely to lead to hyperkeratosis. Frictional forces first cause a hyperkeratotic lesion, which may then develop into a corn. Corns and calluses occur frequently among athletes because of friction of clothing and protective equipment, or poorly fitting shoes. Calluses may actually be advantageous for certain athletes, e.g., on the hands of a baseball player, gymnast, or archer, or on the feet of a runner, basketball player, or dancer. Musicians may also develop and benefit from calluses, e.g., on the upper lip of a trumpet player, fingers of a guitarist, the lower lip of a saxophone player, or the neck of a violinist.



The treatment of corns and calluses begins, first of all, by relieving the causative pressure or friction. Corrective footwear or properly fitted orthotic inserts may relieve excessive external forces. In addition, shoes may be stretched to reduce pressure over existing corns or calluses. Hyperkeratosis caused by shearing of the skin over the metatarsal heads may be helped be evenly distributing the weight through the use of Spence insoles. Hyperkeratosis resulting from an inverted foot may be relieved by support beneath the medial aspect of the foot. Raising the heel may relieve hyperkeratosis resulting from a high arch. Corns may be further treated in the following manner. Soak the corn in hot water. Then, pare the surface with a sharp knife or razor. Place a soft felt ring around the site, and paint the base with silver nitrate solution (10%). Performing this simple regimen once a week may yield satisfactory results. If this treatment is unsuccessful, topical medications for corn and callus removal may be in order. One option is the use of salicylic acid plaster (40% Mediplast available OTC), which is applied after paring the corn and removing the central core. In a 48-hour cycle the plaster is removed; the white, macerated skin is rubbed off; and the plaster is reapplied. Bichloroacetic acid has been successful with similar treatment methods. For relieving the pain caused by a corn, 0.01 to 0.02 ml of triamcinolone suspension (40mg/ml) injected under the corn may be helpful. In the case of soft corns or hard corns that are unresponsive to local therapy, an orthopedic surgeon should be consulted regarding the need to remove the underlying exostosis. Relief may be provided by open surgical shaving of the bone or by minimal-incision surgery. In which a rotating burr placed through a nick in the skin grinds the exostosis. Treatment may be more prolonged for calluses than for corns. Calluses in the presence of oils remain hard and brittle, but if allowed to absorb water become soft and pliable. After completing the first step in treatment (removing pressure with proper footwear or padding), hydration of the callus followed by paring with a scalpel or rubbing with a pumice stone is advised. Salicylic acid plaster (40% Mediplast available OTC) applied to the callus may help diminish the hyperkeratosis and may relieve pressure and pain. Painful calluses such as fissured heel calluses may be softened with nightly application of propylene glycol (two part to one part water) under plastic occlusion. Some ways to prevent, or at least minimize, the development of undesirable corns and calluses are presented in the following memory jogger.



Athletes might take the following precautions in an attempt to help prevent, or at least minimize, the development of undesirable corns and calluses. - Wear shoes that fit properly. - Wear gear such as gloves, kneepads, or thick socks to protect against friction. - Use corn/callus pads on the feet to reduce pressure on irritated areas. - Stretch the shoes at areas over existing corns and calluses. - When possible, avoid activities that place constant pressure on specific skin areas.



Although friction is an essential part of one's existence, there are treatments available to provide relief from the consequences of friction, such as corn and calluses. The treatments outlined for these hyperkeratotic lesions can provide satisfactory results when carried out faithfully.