Aeroallergen patch testing for patients presenting to contact dermatitis clinics

Abstract

Background: The role of aeroallergens in the production of allergic contact dermatitis or “allergic contact dermatitis-like” atopic dermatitis is controversial. Although techniques and allergens lack standardization, most studies find positive patch test results in 30% to 40% of patients with atopic dermatitis. Objective: Our purpose was to determine the prevalence and clinical significance of positive aeroallergen patch tests in patients undergoing standard patch testing for suspected “nonaeroallergen” allergic contact dermatitis. Methods: One hundred three consecutive patients referred to three university patch test clinics for patch testing were also patch tested with six common aeroallergens in glycerine—dust, mold, cat epithelium, tree, grass, and weed—as well as with a glycerine control. Patches were removed at 48 hours. Readings were performed at this time and at 3 to 7 days after initial application. Results: As determined by history, these 103 patients included 16 patients with both atopic dermatitis and mucosal atopy, 10 patients with atopic dermatitis only, 22 patients with mucosal atopy only, and 55 patients with neither atopic dermatitis nor mucosal atopy. Allergic reactions were seen to one aeroallergen in five patients (three with atopic dermatitis and mucosal allergy, and two with no history of atopy). The prevalence (3 of 16 [18.8%]) of reactions in patients with both atopic dermatitis and mucosal allergy was significantly greater than the prevalence (2 of 87 [2.3%]) in patients with only one or neither of these two atopic disorders ( p = 0.02). None of these aeroallergen contact hypersensitivities were deemed significant in the patients' current dermatitis. However, reactions were of past relevance in two of the three patients with atopic dermatitis and mucosal allergy. Conclusion: In this referral group, none of the six common aeroallergens tested was relevant in the origin of suspected “nonaeroallergen” allergic contact dermatitis. This study suggests that aeroallergen patch testing is of little use in the evaluation of patients referred for routine patch testing for suspected “nonaeroallergen” allergic contact dermatitis. Similar but larger studies inclusive of the assessment of relevance, as well as masked controlled clinical trials assessing the effect of aeroallergen exposure and avoidance, are needed to evaluate this issue more fully.