Relevance of patch testing in patients with nummular dermatitis

Background: A chronic dermatosis like nummular dermatitis may be complicated by contact dermatitis due to an impaired cutaneous barrier. This study is aimed at evaluating secondary contact dermatitis in patients with nummular dermatitis.
Methods: Patch testing with the Indian Standard Series was performed in 50 of 78 patients with a clinical diagnosis of nummular eczema. Significant reactions were graded as per ICDRG criteria.
Results: Significant reactions were noted in 23 of 50 tested patients. The most frequent sensitizers were colophony, nitrofurazone, neomycin sulfate and nickel sulfate (7.14% each) Reactions to antigens in topical medications, cosmetics and toiletries constituted 64.28% of all the reactions.
Conclusions: Patients with nummular dermatitis are at significant risk of developing secondary allergic contact dermatitis, which contributes to the severity and chronicity of their dermatitis. Patch testing has the potential to improve the quality of life in these patients. Hence, patients with chronic recalcitrant nummular dermatitis must be patch tested.