Background: The pathogenic importance of the ubiquitous house dust mite, Dermatophagoides pteronyssinus (Dp), in atopic dermatitis is unclear.
Objective: We aimed to explore the relevance of Dp hypersensitivity in adult patients with atopic dermatitis by using an in vivo topical challenge method and in vitro assays for T-cell reactivity.
Methods: Dp and control skin prick test solutions were applied to the cubital fossae of 20 patients twice daily for 4 days; the severity of dermatitis and pruritus in the challenge sites were determined before and after testing. The same solutions were used in PBMC proliferation assays that included 10% fresh, autologous serum, the latter aimed at maximizing IgE facilitated allergen presentation.
Results: Although most patients had markedly elevated Dp-specific serum IgE levels, only 6 of 20 patients developed increases in cubital fossa dermatitis severity and pruritus scores that were greater at sites of application of Dp solution than at control sites. In addition, PBMC proliferation in response to Dp solution in the presence of autologous serum was significantly greater in the in vivo challenge-positive patients than in those who did not respond to challenge. A subgroup of patients (7/20) also developed transient but pronounced contact urticaria at sites of Dp application.
Conclusion: These findings suggest that hypersensitivity to Dp might be clinically relevant in approximately one third of the adult atopic dermatitis population studied. They also point to methods of identifying patients who might respond to house dust avoidance measures.