Allergic contact dermatitis is a condition that occurs when the skin comes into contact with a substance that produces an allergic reaction (e.g., rash). In most case, these substances (called allergens) are harmless. However, some people are born with or develop a hypersensitivity to them. When exposed to allergens (usually organic substances or chemicals), these people experience an allergic reaction.
Allergic contact dermatitis is the second most common type of contact dermatitis, and occurs more often in patients who have other allergies.
Common causes for allergic contact dermatitis of the foot and ankle are exposure to poison ivy, poison oak, or poison sumac, and exposure to dyes used in shoes and sneakers. Even all-white sneakers are made with dye and rubber, both of which are common allergens that can cause rashes and dry scaly skin in people who are hypersensitive to them.
Allergic contact dermatitis often develops when a person buys a new pair of shoes. Dye and other allergens are present in high concentrations in new shoes and are most likely to cause a reaction.
Heat and perspiration generated during exercise may cause dyes in shoes or sneakers to wick (carry through) to the skin, worsening the condition. The dye may not be visible on the sock or skin, but if the person is allergic to it, a dry, itchy rash may develop within 1 or 2 days.
The same reaction can occur with leather shoes, which also contains dye that can cause an allergic reaction.
Treatment for allergic contact dermatitis usually involves using a topical corticosteroid cream and/or an oral antihistamine. A podiatrist can recommend manufacturers of hypoallergenic shoes that do not cause allergic reactions.
In severe cases, systemic methods such as oral and injectable corticosterioids, antibiotics, and other anti-inflammatory and immunologic agents may be necessary.
Anyone who experiences symptoms of allergic contact dermatitis should consult a podiatrist. The podiatrist will take a skin sample that is examined under a microscope for the presence of dermatophytes and other fungi that live on dead tissues of the hair, toenails, and skin. Red, itchy skin on the feet, especially in athletes and those who exercise regularly, may indicate athlete's foot or other fungal infections.
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