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Medical Author:

Gary W. Cole, MD

Gary W. Cole, MD

Dr. Cole is board certified in dermatology. He obtained his BA degree in bacteriology, his MA degree in microbiology, and his MD at the University of California, Los Angeles. He trained in dermatology at the University of Oregon, where he completed his residency.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Contact Dermatitis Causes

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, nonprotein molecule.
• In order to become allergic to such a substance, one must have had at least one previous exposure that eventually triggers 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 small chemical allergens.
• When these lymphocytes come in contact with the allergen, they release a variety chemicals that are able either directly or by stimulating other cells 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 of the Anacardiaceae family. The allergenic chemical is present in the sap or oil.
• Many other substances can cause allergic reactions, including components of hair dyes or straighteners; the metallic nickel, which is found 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 (Mycifradin, 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 directly damaging and irritating 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, are most likely to develop contact dermatitis.