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Epicutaneous Patch Testing

Patch testing is a type of skin testing that can help to determine if you/your child’s rash/dermatitis is caused by an allergy to certain chemicals (allergens) that come in contact with the skin, also known as an allergic contact dermatitis.  These chemicals may be found in topical medicines, creams, lotions, soaps, clothing, shoes, jewelry, perfumes, cosmetics, and shampoos, among other exposures.  Patch testing does not test for allergies to foods, pollen or other seasonal or environmental allergies.

 

Allergic contact dermatitis results when the immune system becomes sensitized to one or more chemicals through contact with the skin or mucous membranes (e.g. eyes, lips). Specifically, helper T-cells (Th1-cells) become sensitized to small molecular weight chemical allergens, called haptens.  It may take weeks to years of exposure in order to become sensitized, but once sensitized, a rash will develop within several days of exposure to the allergen.

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Common allergens that cause allergic contact dermatitis include the following:

  • metals (nickel, cobalt, gold)
  • corticosteroids (hydrocortisone, clobetasol)
  • preservatives (methylisothiazolinone, formaldehyde)
  • antibiotics (neomycin, bacitracin)
  • fragrances
  • adhesives (acrylates, colophony)

Patterns of allergic contact dermatitis distribution include the following

  • hand dermatitis
  • eyelid dermatitis
  • foot dermatitis
  • lip/oral dermatitis
 

For more specific information on patch testing, including pre-testing instructions and other considerations, please select from the following links: