Font Size

Contact Dermatitis (cont.)

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 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 sap or latex that contaminates damaged 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 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 (atopic dermatitis), are more likely to develop contact dermatitis.
Medically Reviewed by a Doctor on 6/24/2015

Must Read Articles Related to Contact Dermatitis

Poison Ivy, Oak, and Sumac
Allergy: Poison Ivy, Oak, and Sumac Poison ivy, poison oak, and poison sumac can causes an learn more >>
Eczema Eczema is a term frequently used to describe any s...learn more >>

Patient Comments & Reviews

The eMedicineHealth doctors ask about Contact Dermatitis:

Contact Dermatitis - Symptoms

What are the symptoms of your contact dermatitis?

Contact Dermatitis - Treatment

What treatment was effective for your contact dermatitis?

Contact Dermatitis - Experience

Please describe your experience with contact dermatitis.

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 »

Medical Dictionary