Top 10 Causes of Skin Allergy

By Daniel J. DeNoon WebMD Health News
Reviewed by Louise Chang, MD

Jewelry metals and fragrances top the list of substances most likely to cause serious skin rashes, Mayo Clinic dermatologists report. When you get a skin rash after contact with an allergy-causing substance (an allergen) doctors call it allergic contact dermatitis. It can be a devastating condition, says Mayo's Mark D. P. Davis, MD.
"Patients with contact dermatitis can get a very itchy rash from head to toe, or in a confined area," Davis says, in a news release. "If it's on the hands and feet it can be disabling, and patients at times can't do their jobs."
How do you know what causes your itchy rash? Using a panel of common allergens, doctors put a small amount on a patch of skin and see whether there is a reaction. It's called patch testing. Davis' and other Mayo researchers patch tested more than 1,500 patients with a series of up to 73 allergens in their study. The top 10 culprits:

1. Nickel (nickel sulfate hexahydrate). A metal frequently encountered in jewelry and clasps or buttons on clothing.
2. Gold (gold sodium thiosulfate). A precious metal often found in jewelry.
3. Balsam of Peru (myroxylon pereirae). A fragrance used in perfumes and skin lotions, derived from tree resin.
4. Thimerosal. A mercury compound used in local antiseptics and in as a preservative in some vaccines.
5. Neomycin sulfate. A topical antibiotic common in first aid creams and ointments, also found occasionally in cosmetics, deodorant, soap, and pet food
6. Fragrance mix. A group of the eight most common fragrance allergens found in foods, cosmetic products, insecticides, antiseptics, soaps, perfumes, and dental products.
7. Formaldehyde. A preservative with multiple uses. It's found in paper products, paints, medications, household cleaners, cosmetic products, and fabric finishes.
8. Cobalt chloride. Metal found in medical products; hair dye; antiperspirant; objects plated in metal such as snaps, buttons or tools; and in cobalt blue pigment.
9. Bacitracin. A topical antibiotic.
10. Quaternium 15. A preservative found in cosmetic products such as self-tanners, shampoo, nail polish, and sunscreen or in industrial products such as polishes, paints, and waxes.
Davis reported the findings at this week's annual meeting of the American Academy of Dermatology in San Francisco. When a patch test is positive, the best thing for patients to do is to avoid the substance to which they are allergic. Treatment with corticosteroid cream can help -- but 3% of patients are allergic to the cream, Davis says.
How well does patch testing work from the patient's point of view? In another conference report, Mayo's Leigh Ann Scalf, MD, and colleagues surveyed about 1,500 patch-test patients.
More than three out of four said they were at least "somewhat satisfied," and more than half said they were "very satisfied." After testing, 58.3% of patients reported improvement in their condition. Why so few? A third conference report suggests an answer. Davis, Scalf, and Joseph Genebriera, MD, find that fewer than half of patch-test patients remember all of the things that make them itch.