American Medical Association Family Medical Guide - American Medical Association [754]
Corns and Calluses
Corns and calluses are areas of skin that have thickened because of constant pressure and friction. Corns develop on the top or sides of the toes or between the toes. Calluses are larger areas of thickened skin that usually appear on the ball of the foot, on the heel, or over a bunion (see page 989), although they also can develop on the palms of the hands or on the tips of the fingers. Corns and calluses usually develop after wearing new or poorly fitting shoes. Wearing high heels can cause calluses from increased pressure on the ball of the foot. Calluses can develop on the hands in people who do heavy or infrequent manual work. Some people are susceptible to calluses and corns because they have less cushioning tissue between the bones and skin of their feet.
Symptoms and Diagnosis
The tissue under the thickened skin of a corn or callus can be tender. You probably don’t need to see a doctor unless it becomes very painful. However, if you have a corn or callus and have a disorder such as diabetes (see page 889), which decreases sensitivity in the feet, see a doctor right away; poor circulation to the area can cause a deep ulcer to develop in the callus.
Treatment
You can relieve pressure on a corn or callus on your foot by going barefoot every chance you get and by using over-the-counter protective pads. Pads that contain salicylic acid can help dissolve thickened skin. You can soften a callus on your feet or hands with a moisturizer. Gently rub away dead skin from the callus with a pumice stone or file, being careful not to press hard enough to inflame the sensitive tissue underneath. Wear comfortable shoes or protective gloves. The corn or callus should disappear within several weeks. If these measures don’t work, your doctor may trim the corn or callus or use a strong chemical to dissolve it.
Dermatitis
Dermatitis is inflammation of the skin that can result from an allergy but in many cases occurs for unknown reasons. Many types of dermatitis are also known as eczema (see page 120). There are several types of dermatitis or eczema.
Atopic dermatitis
Atopic dermatitis (also called atopic eczema) is a skin reaction associated with allergies. In atopic dermatitis, the skin is much more sensitive than usual to many substances. Environmental factors seem to trigger atopic dermatitis in people who are genetically susceptible. Children are at increased risk of developing atopic dermatitis if they have a family history of other atopic diseases, such as hay fever (see page 914) or asthma (see page 640). Adults with atopic dermatitis have a susceptibility to developing contact dermatitis (see below) or irritant dermatitis (see above right).
Contact dermatitis
Contact dermatitis is a type of atopic dermatitis caused by a reaction to particular substances that have touched the skin. Some skin reactions related to contact dermatitis are relatively mild and do not occur in most people. For example, an allergic reaction to contact with a metal such as nickel may cause a red, flaky, itchy patch of skin where the metal (usually on jewelry such as a watch or earrings) touches the body (see page 120). The reaction may take weeks or months to develop.
Some people have more severe allergic reactions to contact with poison ivy and other plants. A delayed hypersensitivity reaction usually occurs 2 days after contact with the plant. The skin can become red and itchy (even