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Contact Dermatitis

What Is Contact Dermatitis?

Dermatitis is an inflammation of the skin. Contact dermatitis is a localized rash or irritation of the skin caused by direct contact the inducing substance to which the skin reacts. Such substances are toxic to the skin and are termed primary irritants. Others may induce an immunologic reaction called allergic contact dermatitis and include plant oils, metals, cleaning solutions, cosmetic additives, perfumes, industrial chemicals, topical antibiotics, and latex rubber additives.

What Are Causes of Contact Dermatitis?

There are two types of contact dermatitis: allergic and irritant. They often can appear to be visually identical.

  • Allergic contact dermatitis often results from an immune response to a small, structurally simple molecule.
    • In order to become allergic to such a substance, one must have had at least one previous exposure that eventually induces an immune response.
    • This dermatitis is not caused by an antibody but is due to a cellular immune response mediated by a type of blood cell (T-lymphocytes) that has surface molecules that enable it to recognize specific chemical allergens.
    • When these lymphocytes come in contact with the allergen, they release a variety chemicals that are able to produce an itchy dermatitis.
    • Typically, this sort of reaction occurs only on the skin and requires at least 24 to 48 hours to develop.
    • Common plants that produce allergic contact dermatitis include poison ivy, poison oak, and poison sumac. The allergenic chemical is present in the oil or latex that covers stems or leaves.
    • Many other substances can cause allergic reactions, including components of hair dyes or straighteners; metallic nickel in jewelry and belt buckles; leather tanning agents; and chemical additives to latex rubber.
    • The fragrances in soaps and preservatives and emulsifiers in shampoos, lotions, perfumes, and cosmetics can cause reactions.
    • Medications applied to the skin, like neomycin (Neosporin, Neo-Fradin, Neo-Tab), are a common cause of this type of dermatitis.
  • Irritant contact dermatitis results from coming in contact with a substance that is directly toxic to your skin. No allergy is required, and it will occur on the first exposure.
    • The longer the substance remains on the skin, the more severe the reaction.
    • Many chemicals, including industrial cleaning products and solvents, can cause this condition.
    • Household cleaners such as detergents can also cause dermatitis.
  • People with other skin conditions, such as eczema (atopic dermatitis), are more likely to develop contact dermatitis.
Medically Reviewed by a Doctor on 3/30/2017

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Patient Comments & Reviews

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Contact Dermatitis Sign

Rash

Rash is a general, nonspecific term that describes any visible skin outbreak. Rashes are very common in all ages, from infants to seniors, and nearly everyone will have some type of rash at some point in their life. There are a wide variety of medical diagnoses for skin rashes and many different causes.


Read What Your Physician is Reading on Medscape

Contact Dermatitis, Allergic »

The term contact dermatitis sometimes is used incorrectly as a synonym for allergic contact dermatitis (ACD).

Read More on Medscape Reference »


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