Corns and calluses
Corns and calluses are thickened, protective patches of skin that develop in response to repeated friction or pressure, primarily on the feet and hands. Corns, or clavi, typically arise from pressure on areas of thin skin and can be painful, presenting as small, smooth lesions with a hard surface. They are classified into hard corns, which have a conical shape, and soft corns, which often form in moist areas between toes and may become inflamed. Calluses, or tylomas, occur on thicker skin areas and are generally painless; they cover larger surfaces and lack a central core.
Both conditions serve as a defense mechanism against ongoing pressure, often resulting from ill-fitting footwear or manual labor. Treatment usually focuses on alleviating the source of friction, such as opting for well-fitted shoes and using protective padding. Over-the-counter treatments may help soften the thickened tissue, and in some cases, professional removal or surgery may be necessary if complications arise. Understanding these skin conditions can help individuals manage symptoms effectively and prevent further issues.
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Subject Terms
Corns and calluses
Anatomy or system affected: Feet, hands, skin
Definition: Areas of thickened skin that form as a result of constant pressure or friction over a bony prominence
Causes and Symptoms
Both corns (clavi) and calluses (tylomas or tyloses) occur when chronic pressure or friction causes hypertrophy of the dermal skin layer and a proliferation of keratin as a protective response. Both corns and calluses usually occur on the feet. Corns develop from pressure on normally thin skin. Calluses develop over areas where the skin is normally thicker. They commonly develop on the plantar (sole) surface of the foot and on the palmar (palm) surface of the hand. Corns are frequently painful, whereas calluses usually are not painful. Corns are small, flat, or slightly elevated lesions with a smooth, hard surface. Calluses cover a larger area than corns and are less well-demarcated.
There are two classifications of corns: hard and soft. Hard corns have a conical structure composed of keratin, with the point of the cone directed inward, causing pain when pressed into the soft, underlying tissue. Hard corns have a circumscribed border that demarcates the lesions from the surrounding soft tissue. Hard corns usually develop on the top or sides of the toes, where shoes press on the interphalangeal joints of the toes, or the plantar surface of the foot, where pressure is exerted against bony prominences.
Soft corns develop in areas where a bony prominence causes constant pressure against soft tissue, resulting in a blanched thickening of the skin. Because soft corns commonly develop on interdigital surfaces, such as between the fourth and fifth toe, they are characteristically moist and macerated and can become inflamed.
Calluses develop as a protection against continual pressure. They do not have the central core of keratin and, as a result, are not sensitive to pressure. Normal skin markings are present over callused areas. Calluses usually develop on weight-bearing areas of the foot under the metatarsal heads and the heel. Calluses on the palm are frequently the result of manual occupations.
Treatment and Therapy
Treatment of corns and calluses depends on symptoms. Since corns and calluses are caused by chronic pressure, preventive measures include removing the source of friction or pressure. Well-fitting shoes that do not crowd the toes relieve pressure on interdigital areas. Soft, sufficiently wide, or open-toed shoes are good choices. Soft insoles and properly fitting socks or stockings also reduce pressure. Wrapping lamb’s wool or other padding over pressure points can increase air circulation and reduce pressure and discomfort. Corns and calluses can be treated with over-the-counter keratolytic agents. Salicylic acid plasters are used to soften the tissue, which can then be removed with a pumice stone. When corns, or occasionally calluses, become inflamed or painful, they can be removed by paring or trimming. This should be done by a health care provider, especially in patients with compromised circulation to the feet. In rare circumstances, surgery may be required if a corn or callus becomes infected or if the chronic pressure on particular areas is caused by a structural abnormality of the foot, such as a hammertoe, an abnormal bend in the toe joint.
Bibliography
Copeland, Glenn, and Stan Solomon. The Foot Doctor: Lifetime Relief for Your Aching Feet. Rev. ed. Macmillan Canada, 1996.
"Corns and Calluses." American Podiatric Medical Association, www.apma.org/corns. Accessed 20 July 2023.
"Corns and Calluses." Mayo Clinic, 16 Dec. 2022, www.mayoclinic.org/diseases-conditions/corns-and-calluses/diagnosis-treatment/drc-20355951. Accessed 20 July 2023.
Lippert, Frederick G., and Sigvard T. Hansen. Foot and Ankle Disorders: Tricks of the Trade. Thieme, 2011.
Lorimer, Donald L., et al., eds. Neale’s Disorders of the Foot. 8th ed. Churchill Livingstone/Elsevier, 2010.
Mackie, Rona M. Clinical Dermatology. 5th ed. Oxford University Press, 2003.