Contact dermatitis is an inflammation of the skin that results from contact with an inciting substance. More than 50 percent of cases occur on the hands. Irritant contact dermatitis, the most common type, is direct damage from contact with a harmful chemical. Doctors distinguish irritant contact dermatitis from allergic contact dermatitis, or ACD. The rashes may look similar, but allergic contact dermatitis results from an immune response to a substance, explains a January 2006 review article published in the journal "Medical Clinics of North America."
Appearance
Allergic contact dermatitis occurs only in a subset of people who are allergic to a substance. According to the American Academy of Dermatology, the first exposure to a chemical doesn't cause a reaction but "sensitizes" the immune system to that chemical. The next exposure sets off the immune cascade resulting in a red, scaly rash with tiny blisters called vesicles at the site of skin contact with the substance. The rash appears 12 to 48 hours after this second exposure. As the vesicles erupt, the rash oozes and eventually crusts.
Common Causes
Allergic contact dermatitis of the hands has several common causes. Poison ivy represents the classic delayed hypersensitivity reaction of ACD. More than 70 percent of the U.S. population would have an allergic reaction to the oil from the plant. According to the American Academy of Dermatology, nickel is another common allergen, often found in jewelry. The presence of sweat worsens allergic reactions to nickel. Fragrances and preservatives in lotions often cause rashes on the hands of allergic individuals as well, according to the academy. Topical antibiotics---for example, neomycin and bacitracin---that people frequently apply to cuts or abrasions account for other cases of ACD in the general population.
Occupational Hazards
A March 2000 article in the "Journal of Allergy and Clinical Immunology" estimates that ACD accounts for approximately $250 million dollars per year in workplace-related medical costs. In 2004, a study in the journal "Dermatitis" found that over half of hand dermatitis cases resulted from workplace exposure. The article also explains that healthcare workers are most frequently affected on the job, often as a result of ACD reactions to latex or other components of rubber gloves. Hair stylists are also commonly affected. According to the American Academy of Dermatology, hair color includes the ingredient paraphenylene diamine, a common allergen that can cause a reaction on the hands of a stylist who applies the coloring. Other commonly affected workers are mechanics, welders and construction personnel who work with materials that contain chromates.
Testing
Nearly 3,000 chemicals have been identified as causative agents of ACD, which complicates the diagnosis of ACD by making it difficult to pinpoint the responsible substance. Patch testing involves the application of a panel of suspected allergens on a patient's skin. Patients and their physicians observe the skin for a reaction during the next three days. This simple test is over 100 years old, according to the "Medical Clinics of North America," review and is still considered the gold standard for obtaining a diagnosis.
Treatment
Avoiding further contact with a responsible agent is the first and most important step in treating ACD. Additional treatments outlined in the "Journal of Allergy and Clinical Immunology" includes steroid medications, which have anti-inflammatory and immune-modulating properties. A doctor may prescribe them for topical application or as a pill. Light therapy provides another possible treatment. A qualified physician should prescribe or supervise all treatments.
References
- "Medical Clinics of North America"; Allergic Contact Dermatitis; B. J. Mark and R. G. Slavin; January 2006
- American Academy of Dermatology: Allergic Contact Rashes
- "Journal of Allergy and Clinical Immunology"; The Diagnosic Evaluation, Treatment, and Prevention of Allergic Contact Dermatitis in the New Millennium; Donald V. Belsito, MD; March 2000
- "Dermatitis"; Etiology of Hand Dermatitis among Patients Referred for Patch Testing; J. T. Templet, et al.; 2004
