Aeroallergen patch testing in patients of suspected contact dermatitis

Background: Aeroallergens are airborne substances present in the environment with the potential to trigger an allergic reaction in the respiratory tract, mucosae, or skin of susceptible individuals. The relevance of aeroallergens in the pathogenesis of atopic dermatitis has been reported by many investigators. However, very few studies have been conducted to investigate their role in the production of allergic contact dermatitis (ACD). Aims: To determine the prevalence of aeroallergen patch test positivity in patients of suspected ACD and to study the clinical characteristics of patients testing positive with aeroallergens. Materials and Methods: Patients presenting to our department with suspected contact allergy and undergoing patch testing with Indian Standard Series (ISS) between January 2010 and June 2011 were studied. After a detailed history and clinical examination, patients were patch tested with ISS and aeroallergen series. Based on the history and clinical suspicion, patients were additionally patch tested with 15% Parthenium. Prior tape stripping was done in some patients. Results: Out of total 114 patients, 26 (22.8%) showed sensitivity to aeroallergen series. Parthenium was the commonest aeroallergen being positive in all 26 patients followed by Xanthium in two. None reacted to other allergens. Although positivity was more in patients with prior tape stripping, the difference was not statistically significant. Conclusion: Most common aeroallergen found to be positive in our study was Parthenium hysterophorus. In view of low positivity to other allergens, routine aeroallergen patch testing in patients with suspected contact dermatitis may not be necessary.