Calluses and corns are circumscribed areas of hyperkeratosis at a site of intermittent pressure or friction. Calluses are more superficial, diffuse, and are usually asymptomatic. Corns are deeper, more focal, and frequently painful. Diagnosis is based on appearance. Treatment is with manual abrasion with or without keratolytics. Prevention involves altering biomechanics, such as changing footwear. Rarely, surgery is required.
Topic Resources
Calluses and corns are caused by intermittent pressure or friction, usually over a bony prominence (eg, calcaneus, metatarsal heads).
Corns consist of a sharply circumscribed keratinous plug, pea-sized or slightly larger, which extends through most of the underlying dermis. An underlying adventitial bursitis may develop. Hard corns occur over prominent bony protuberances, especially on the toes and plantar surface. Soft corns can occur between the toes. Most corns result from poorly fitting footwear, but small seed-sized corns on non–weight-bearing aspects of the soles and palms may represent inherited keratosis punctata.
Calluses lack a central plug and have a more even appearance. They usually occur on the hands or feet but may occur elsewhere, especially in a person whose occupation entails repeated trauma to a particular area (eg, the mandible and clavicle of a violinist).
Layers of the Skin
In this figure, the 5 layers of the epidermis along with its basement membrane and the dermis can be seen. Note that the stratum lucidum is present over the palms and soles only. The basement membrane is disproportionately enlarged to display its layers. The sublamina densa anchors the dermis to the upper layers of the basement membrane. |
Symptoms and Signs of Calluses and Corns
Calluses are usually asymptomatic but, if friction is extreme, may become thick and irritated, causing mild burning discomfort. At times, the discomfort of calluses near the toes may mimic that of interdigital neuralgia.
Corns may be painful or tender when pressure is applied to them. A bursa or fluid-filled pocket sometimes forms beneath a corn.
Diagnosis of Calluses and Corns
History and physical examination
A corn may be differentiated from a plantar wart or callus by paring away the thickened skin.
After paring, a callus shows smooth translucent skin, whereas a wart appears sharply circumscribed, sometimes with soft macerated tissue or with central black dots (bleeding points) representing thrombosed capillaries. Also, warts disrupt dermatoglyphs (the unique pattern of ridges on the skin of the fingers, palms, toes, and soles) while calluses do not.
A corn, when pared, shows a sharply outlined yellowish to tan translucent core that interrupts the normal architecture of the papillary dermis.
Treatment of Calluses and Corns
Manual removal
Keratolytics
Cushioning
Altering foot biomechanics
Sometimes expert foot care
Manual removal
A nail file, emery board, or pumice stone used immediately after bathing is often the most practical way to manually remove hyperkeratotic tissue.
Keratolytics
Keratolytics (eg, 17% salicylic acid in collodion, 40% salicylic acid plasters, 40% urea) can also be used, taking care to avoid applying the agents to unaffected skin. Surrounding skin may be protected by covering it with petrolatum before application of the keratolytic.(eg, 17% salicylic acid in collodion, 40% salicylic acid plasters, 40% urea) can also be used, taking care to avoid applying the agents to unaffected skin. Surrounding skin may be protected by covering it with petrolatum before application of the keratolytic.
Cushioning and foot biomechanics
Cushioning and altering foot biomechanics can help to both prevent and treat corns. Although difficult to eliminate entirely, pressure on the affected surface should be reduced and redistributed to prevent recurrence or exacerbation of existing lesions.
For foot lesions, soft, well-fitting shoes are important; they should have a roomy toe box so that toes can move freely in the shoe. Stylish shoes can often prevent this freedom of motion. Shoes that increase the discomfort of a lesion should be eliminated from the wardrobe. Pads or rings of suitable shapes and sizes, moleskin or foam-rubber protective bandages, arch inserts (orthotics), or metatarsal plates or bars may help redistribute the pressure.
For corns and calluses on the plantar surface of the metatarsals, an orthotic should not be full length but should extend only to the part of the foot immediately behind the corn or callus. Surgical off-loading or removal of the offending bone is rarely necessary.
Expert foot care
Patients who have a tendency to develop recalcitrant painful calluses and corns may need regular care from a podiatrist.
Patients who also have impaired peripheral circulation, particularly if they also have diabetes, require intensive foot care.
Key Points
The cause of corns and calluses is usually intermittent pressure or friction, usually over a bony prominence.
After paring away the thickened overlying skin, a wart will bleed, whereas a corn will not.
Mechanical abrasion and keratolytics can be used to help remove corns and calluses.
Cushioning and redistributing pressure in the foot is recommended to help prevent corns and calluses.
