365 Patch Testing Results in Contact Dermatitis from the Allergist's Perspective

BACKGROUND: Contact Dermatitis (CD) is a frequently encountered skin disease by allergists and dermatologists that results from contact with external allergens. Patch Testing (PT) remains the gold standard in the diagnosis of allergic CD. Studies evaluating PT from allergy practices are lacking. METHODS: A multi-center, retrospective chart review of PT within the last 5 years at allergy practices in 3 institutions. We report PT results using allergens in the Thin-Layer Rapid-Use Epicutaneous Test (TT) and additional supplemental allergens [North American Contact Dermatitis (NACD) Panel, Dormer Cosmetic Panel, hairdresser's panel, corticosteroid panel and personal products]. Additionally, patient characteristics including age, gender, occupation, dermatitis site, history of atopic disease and final diagnosis were also obtained. RESULTS: A total of 427 patients (mean age = 49.8 years) were patch tested, 82% were female, 54% reported an atopic history (history of asthma, atopic dermatitis, allergic rhinitis or food allergy), 30% were tested with TT, 60% with NACD panel, 30% with cosmetic series, 15% with corticosteroid series and 35% with personal products. The 5 most common positive PT allergens were nickel sulfate, fragrance mix I, P-phenylenediamine, thimerosal and cobalt chloride. The most common dermatitis sites were eyelid/periorbital (31%), facial (25%) and trunk (21%). 56.9% of patients were positive to at least one TT allergen. 25.6% of patients were positive to both a TT and a supplemental allergen (these patients would have been “partially evaluated” with TT allergens alone as they are positive to at least 1 TT allergen and 1 supplemental allergen). 12.5% of patients were negative to a TT allergen and positive to at least 1 supplemental allergen only (these patients would have been “missed” as they are negative to all TT allergens, but positive to at least 1 supplemental allergen). CONCLUSIONS: Nickel remains the most common allergen. When evaluating patients with CD, testing with TT allergens alone would miss 12.5% of patients while 25.6% of patients would be only partially evaluated. As half of our patients were positive to at least 1 TT allergen, the TT remains an adequate screening tool but a more comprehensive panel may be needed to fully evaluate contact dermatitis.