Because both atopic dermatitis (AD) and contact dermatitis (CD) are characterized by a similar morphologic appearance and similar distribution of skin involvement, the diagnosis of CD in AD has been difficult. Recent studies have shown that patients with AD have similar if not higher rates of positive patch test results to common contact allergens, including metals and fragrance compared to patients without AD.
AD and CD have common areas of involvement, including the lips, eyelids, hands, and flexural areas which oftentimes make it difficult to diagnose one disease instead of the other. Patch testing should be considered when clinically suspicious for contact dermatitis. Consider CD in patients with AD and who have disease that is difficult to control, worsens with therapy, or spreads to new or previously unaffected sites. Suspect CD to topical corticosteroids, antiseptics, antibiotics, and emollients of patients with AD. Patch testing is performed with preloaded series (T.R.U.E. Test) or allergens that are manually loaded onto chambers. The use of personal products as supplemental allergens is suggested in patients with suspected cosmetic dermatitis. Once contact allergens have been identified from testing, avoidance of allergens is indicated. The advantage is implementation of an avoidance regimen. A period of 8-12 weeks of allergen avoidance has been suggested.